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LO 3.36: The student is able to describe a model that expresses the key elements of signal transduction pathways by which a signal is converted to a cellular response. SP 1.5: The student can re-express key elements of natural phenomena across multiple representations in the domain.

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M.C. Question: Which of the following about receptor Tyrosine Kinases is false?


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    1. LO 3.36: The student is able to describe a model that expresses the key elements of signal transduction pathways by which a signal is converted to a cellular response. SP 1.5: The student can re-express key elements of natural phenomena across multiple representations in the domain. Explanation: There are three main stages of cell signaling. These stages are reception, transduction, and response. In reception, a chemical signal acts as a ligand and binds to a receptor. These receptors may include G-protein-linked receptors, receptor Tyrosine Kinases, Ion Channel receptors, and intracellular receptors. The binding of the signal molecule will in some way change the shape of the receptor. This is what begins the transduction stage. In transduction, kinases add a phosphate group to relay proteins. This activates second messengers such as cAMPto pass along the signal. This then leads to the final stage, response. The response is always specific to the signal molecule that started this process. The most common examples of a response are the transcription of a gene into mRNA and also the translation of mRNA into a protein that has a specific function. M.C. Question: Which of the following about receptor Tyrosine Kinases is false? A) They can trigger more than one signal transduction pathway at once. B) They are involved in cell reproduction. C) The receptor is a dimer before the signal molecule binds.D)The receptor has two binding sites. E) The receptor attaches phosphates to tyrosines. Learning Log/FRQ style question: Compare and contrast the differences between membrane-bound receptors and intracellular receptors.

    2. Answer Key- LO 3.36 Which of the following about receptor Tyrosine Kinases is false? A) They can trigger more than one signal transduction pathway at once. B) They are involved in cell reproduction. C) The receptor is a dimer before the signal molecule binds.D) The receptor has two binding sites. E) The receptor attaches phosphates to tyrosines. Compare and contrast the differences between membrane-bound receptors and intracellular receptors. Membrane-bound receptors are located in the plasma membrane of a cell. Their ligands are water soluble and are too large to pass through the membrane without any assistance. These include G-protein-linked receptors, receptor tyrosine kinases, and ion channel receptors. Once the signal molecule binds to the receptor, it causes a transduction pathway which leads to a specific cellular response. On the other hand, intracellular receptors are located either in the cytoplasm or in the nucleus. The signal must be able to freely pass through the plasma membrane in order to be able to bind to this type of receptor. This may either be due to the signal molecule being very small in size or to it being hydrophobic. Most molecules that bind to intracellular receptors are hydrophobic steroid hormones. When the signal molecule binds to the receptor, it stimulates the transcription of the gene into mRNA which is then translated into a specific protein.

    3. LO 1.29: The student is able to describe the reasons for revisions of scientific hypotheses on the origin of life on Earth. SP 6.3: The student can articulate the reasons that scientific explanations and theories are refined or replaced. • Explanation:Scientific hypotheses are revised when new evidence arises that changes previous thoughts. Primitive Earth was very different than the Earth known today. There was little oxygen, but much more water, carbon monoxide, carbon dioxide, and ammonia. There was a lot of lightning, volcanic activity, UV radiation, and meteorite bombardments. In the 1920s, Oparin and Haldane hypothesized that early Earth was a reducing (electron adding) environment, in which organic compounds were formed by inorganic compounds. The energy for these reactions would have been powered by lightning and UV radiation. Haldane proposed that early oceans were solutions of organic molecules, “primitive soup”, from which life arose. In 1953, the Miller-Urey experiment tested Oparin and Haldane’s hypothesis. They created lab conditions comparable to those that existed on early Earth, and is shown in the figure below. This experiment yielded all 20 amino acids, several sugars, purines and pyrimidines, ATP (when phosphate is added), and all monomers. Many labs have since repeated this experiment using different recipes for atmosphere, and organic molecules were also produced in some of those. Sydney Fox then expounded on the previous hypotheses, and to show how these monomers connected to make polymers, dripped monomers on hot sand, clay, or rocks. This created proteinoids -polypeptides created by abiotic means. The next step is protobionts, which are abiotically produced molecules surrounded by a membrane. They are primitive cells with imprecise reproduction and a simple metabolism. • Multiple Choice Question: • In which of these cases would organic molecules most likely • NOT be created in a Miller-Urey type experiment? • A) There was high levels of UV radiation • B) produced in something similar to the “primitive soup” • C) the environment was not reducing • D) methane was present • FRQ: • Describe in detail the Miller-Urey experiment. Then, • discuss how this experiment, and the Fox experiment, fit into • the timeline of the origin of life from inorganic molecules to • protobionts.

    4. Answer Key- LO 1.29 • In which of these cases would organic molecules most likely NOT be • created in a Miller-Urey type experiment? • A) There was high levels of UV radiation • B) produced in something similar to the “primitive soup” • C) the environment was not reducing • D) methane was present • Describe in detail the Miller-Urey experiment. Then, discuss how this experiment, and the Fox experiment, fit into the timeline of the origin of life from inorganic molecules to protobionts. • The first stage of the Miller-Urey experiment, water was heated and the vapor traveled upward. There, it came in contact with hydrogen gas, methane, and ammonia, and was shocked by electrodes. Then, it condensed and cooled. The now cooled water containing the organic molecules was then sampled for a chemical analysis. This experiment simulates the conditions scientists postulate existed on early Earth and demonstrate how organic molecules were made from inorganic molecules. The ammonia, methane, and hydrogen gas in the atmosphere and in the “primitive soup” oceans would have come in contact with the lightning, simulated by the electrodes, combining to make organic molecules. Next, these monomers would have combined to make polymers by interacting, as Fox hypothesized and tested, on hot sand, clay, or rocks, to make proteinoids. After, theses proteinoids combined to create protobionts which were the first primitive cells.

    5. LO 1.27 The student is able to describe a scientific hypothesis about the origin of life on Earth.SP 1.2 The student can describe representations and models of natural or man-made phenomena and systems in the domain Explanation: It is believed that the origin of life on Earth began through simple cells that were created though four main stages: 1)The abiotic synthesis of small organic molecules 2) The joining of these monomers into polymers 3) The packaging of these molecules into protobionts 4) The origin of self replicating molecules. The first atmosphere of Earth was thick with water vapor, nitrogen, carbon dioxide, methane, ammonia, and hydrogen. Abiotic synthesis of organic molecules was facilitated by the reducing environment of early earth, mixed with organic molecule solution from the oceans and charged by lightning or UV radiation. This theory was tested by Miller and Urey who simulated the former conditions in the lab and indeed synthesized organic molecules, such as amino acids and nucleotides. These monomers are then abiotically joined into polymers through dripping amino acids onto hot clay, sand, or rock. The polymers formed spontaneously and of their own accord, with each polymer being original. These macromolecules (proteins and nucleic acids)could now serve as weak catalysts for reactions. The macromolecules aggregated and were surrounded by a membrane-like structure. These were known as protobionts which performed some of the properties of life such as reproduction, metabolism, and maintaining an internal chemical environment different from its surroundings. Protobionts used molecules around them and synthesized some until they were replaced by organisms that produced all needed compounds from the environment. Diversification occurred and led to autotrophs and heterotrophs which were the first prokaryotes. Endosymbiosis followed, in which the prokaryotes, chloroplasts and mitochondria, were ingested by a larger cell, resulting in interdependence and the creation of a single organism which would be the eukaryotic cell. FRQ: Use three of the four following terms to identify and explain a scientific hypothesis regarding the origins of life on Earth. i) polymers ii) protobionts iii) Endosymbiosis iv)lightning/UV radiation MC: Which of the following are regarded as essential to the origins of life i. the biotic synthesis of polymers ii. The maintained internal chemical state of protobionts iii. Endosymbiosis of chloroplast/mitochondria and a host cell a) i b) ii c) iii d) i and iii e) ii and iii

    6. Answer Key MC: Which of the following are regarded as essential to the origins of life i. the biotic synthesis of polymers ii. The maintained internal chemical state of protobionts iii. Endosymbiosis of chloroplast/mitochondria and a host cell • i b) ii c) iii d) i and iii e) ii and iii FRQ: Use three of the four following terms to identify and explain a scientific hypothesis regarding the origins of life on Earth. i) polymers ii) protobionts iii) Endosymbiosis iv)lightning/UV radiation In early Earth, monomers were synthesized abiotically from gasses in the atmosphere such as hydrogen, methane, and ammonium along with energy from lightening/UV radiation. Polymers were created by monomers being dropped onto hot clay, sand, or rock and spontaneously forming into macromolecules such as proteins or nucleic acids. The macromolecules would join together with a membranous structure surrounding, making them into protobionts. Protobionts were key as not only could they reproduce and metabolize, but they could maintain their own internal chemical balance that was different from the rest of the environment. Protobionts led to diversification and the first prokaryotes, which became essential to endosymbiosis as chloroplasts and mitochondria were enveloped by a host cell and became integrated into it, resulting in a eukaryotic structure.

    7. LO 2.19 The student is able to make predictions about how positive feedback mechanisms amplify activities and processes in organisms based on scientific theories and models. SP 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models. Explanation: Positive feedback mechanisms amplify responses in biological organisms, and moving farther away from the target set point. Some common examples of positive feedback would be with labor in childbirth, ripening of fruits, and lactation in animals. In childbirth, the pressure that is caused by the baby’s head against receptors near the opening of the uterus stimulates uterine contractions. These cause greater pressure against the opening, which increases the contractions, and this causes more pressure. With positive feedback, it completes childbirth. With lactation in mammals, the suckling on the mothers breasts produces prolactin, which leads to milk production. More suckling leads to more prolactin which leads to more to milk production which then leads to more lactation. This is one of few examples of positive feedback since the product which is milk leads to more suckling which leads to more lactation. Positive feedback can cause instability in an environment. M.C. Question: Which of the following statements is an example of positive feedback? A)When humans body temperature drops too low, the body shivers to bring it back up B)Predator-prey relationships – if the number of prey decreases, the predator will starve C)Blood clotting – when the vessel is injured, platelets cling to the injured site and release chemicals to attract more platelets. The platelets continue to come until a clot is formed D)Blood sugar regulation in humans. When it rises, insulin sends a signal to the liver to store the glucose Learning Log/FRQ-style Question: What is the difference between positive feedback and negative feedback? Give an example of each. Identify which is more common, positive feedback or negative feedback?

    8. ANSWER KEY - LO 2.19 Which of the following statements is an example of positive feedback? A)When humans body temperature drops too low, the body shivers to bring it back up B)Predator-prey relationships – if the number of prey decreases, the predator will starve C)Blood clotting – when the vessel is injured, platelets cling to the injured site and release chemicals to attract more platelets. The platelets continue to come until a clot is formed D)Blood sugar regulation in humans. When it rises, insulin sends a signal to the liver to store the glucose What is the difference between positive feedback and negative feedback? Give an example of each. Identify which is more common, positive feedback or negative feedback? Positive feedback is when the rate of a process increases as the amount of product increases. Negative feedback is the opposite, and is when the rate of the process decreases as the amount of product increases. In negative feedback, the output reduces the effect of the stimulus while in positive feedback the output enhances the stimulus. An example of negative feedback would be sweating. When our body temperature gets too high, negative feedback works to try and stop the temperature from increasing, thus we start sweating. An example of positive feedback would be during childbirth when the body releases the hormone oxytocin to speed up contractions. This increase in the hormone causes there to be more contractions which then causes more oxytocin to be released and this goes on until the baby is born and positive feedback is stopped. Out of the two, negative feedback is more common.

    9. Hypothalamus Neurosecretory cells of the hypothalamus Axon Posterior pituitary Anterior pituitary ADH HORMONE Oxytocin Mammary glands, uterine muscles TARGET Kidney tubules LO4.9: The student is able to predict the effects of a change in a component(s) of a biological system on the functionality of an organism(s). SP6.4: The student can make claims and predictions about natural phenomena based on scientific theories and models. Explanation: Biological systems, like the Endocrine system contain many components that aid in the function of the system. For example, the hypothalamus plays an important role in the system by receiving information from nerves throughout the body and from other parts of the brain and initiates endocrine signals appropriate to conditions. The hypothalamus contains neurosecretory cells that store and regulate hormonal secretions in the pituitary gland. The posterior pituitary gland is an extension of the hypothalamus. Specific neurosecretory cells make the ADH hormone which increases water retention and decreases urine volume. The neurosecretory cells also make oxytocin which forces target cells in the uterine muscles to contract during childbirth. If a change in secretion of ADH occurs, then water retention would potentionally decrease and cause an increase of urine volume. Using the idea of the role of the posterior pituitary gland, it is easily able to lead to predictions of the role of the anterior pituitary gland. M.C Question: Which of the following would most likely occur due to the inhibition of the thyroid glands? • An Increase in blood glucose • Lack of regulation of T3 and T4 secretion • Retention of sodium ions and water by kidneys • Build up of proteins and fats leading to decreased blood glucose FRQ: Choose one of the biological systems listed below and list the components and function of the system. • Endocrine • Nervous • Respiratory Explain the effects of inhibition of one of the components in the system mentioned above.

    10. Answer Key-LO 4.9 Which of the following would most likely occur due to the inhibition of the thyroid glands? • An Increase in blood glucose • Lack of regulation of T3 and T4 secretion • Retention of sodium ions and water by kidneys • Build up of proteins and fats leading to decreased blood glucose Choose one of the biological systems listed below and list the components and function of the system. • Endocrine • Nervous • Respiratory Explain the effects of inhibition of one of the components in the system mentioned above. The central nervous system is made up of the brain and spinal cord. The peripheral nervous system is made up of the nerve fibers that branch off from the spinal cord and extend to all parts of the body, including the neck and arms, torso, legs, skeletal muscles and internal organs. The brain sends messages through the body to control the movement of the muscles and the function of internal organs. The messenger of the nervous system are neurons. Neurons communicate with each other using axons and dendrites. When a neuron receives a message from another neuron, it sends a signal down the length of its axon. At the end of the axon, the electrical signal is converted into a chemical signal, and the axon releases messengers called neurotransmitters. The neurotransmitters are released into the between the end of an axon and the tip of a dendrite from another neuron, asynapse. If the neurons were inhibited, then the brain would not be able to send messages through the rest of the body to send signals to create movements and functions of other parts of the body and internal organs.

    11. LO 4.23: The student is able to construct explanations of the influence of environmental factors on the phenotype of an organism. SP 6.2: The student can construct explanations of phenomena based on evidence produced through scientific practices. Explanation: The interactions between diverse environment conditions, multiple genetic loci and possible phenotypic expression is unpredictable and therefore a constant topic of study for scientists. The use of microarray analysis allows for the examination of thousands of genes, in differing environmental conditions, at once in order to better understand the relationship between phenotype and the environment. There are an endless amount of environmental factors that can alter an organism’s phenotype including: temperature, diet, and light cycles.The ability for phenotype to be altered by environmental changes is referred to as phenotypic plasticity. This is what allows organisms to cope with their environment and what increases their chances of survival. The higher the phenotypic plasticity, the greater the organism’s ability to adapt and survive in changing environments.Variations in an organism’s habitat can also trigger modes of natural selection such as directional, disruptive, and stabilizing. Directional selection occurs when an environment is unlike the organism’s original habitat, shifting the entire makeup of the population so that the individuals with the favored characteristic will survive and produce offspring. Disruptive selection is when conditions favor organisms on both extremes of a phenotypic range. And stabilizing selection favors intermediate variants in the population, maintaining a specific phenotype’s average success. The shift in favored phenotypic expression among populations creates a higher rate of reproductive success for those organisms and thus increases the rate of survival. M.C. Question: Which of the following does not represent an environmental factor that could alter an organism’s phenotype? a) Temperature b) Soil Acidity c) Meiosis d) Predation FRQ Question: 1a) Choose two of the following factors to evaluate the correlation between an organism’s phenotype and the environment. Temperature pH Diet

    12. Answer Key (L.O. 4.23) M.C. Question: Which of the following does not represent an environmental factor that could alter an organism’s phenotype? a) Temperature- This may change the thickness of an organism’s coat to protect against environmental conditions b) Soil Acidity- The color of flowers changes due to the soil’s properties c) Meiosis- Sexual reproduction does not involve an organism’s outside environment d) Predation- Organisms may be forced to develop protection or camouflage against predators in their environment FRQ Question: 1) Choose two of the following factors to evaluate the correlation between an organism’s phenotype and the environment. • Temperature • pH • Diet FRQ Response: In the case of the arctic fox, the environment’s temperature effects the color of the fox’s coat. The summer months produce a brown coat for the fox, and the winter season causes the coat to turn white. These changes allow for the fox to survive more successfully by its ability to blend in with its surroundings. The acidity of soil has a similar color-changing effect for some flowers. Hydrangeas, for instance, will bloom blue flowers with a lower pH balance in the soil; however, if the soil is more neutral a pink color will appear. These two shifting environmental conditions happen to change the color of the organisms- targeting that specific phenotypic characteristic in the two individuals.

    13. LO 2.14:The student is able to use representations and models to describe differences in prokaryotic and eukaryotic cells.SP 1.4: The students can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Explanation: Prokaryotic and eukaryotic cells, while both contain the materials necessary for life, are different in many aspects. One noticeable difference is that eukaryotic cells are bigger than prokaryotic cells. Eukaryotic cells contain many “organelles,” organized membrane-bound structures that help the cell function by performing specific tasks, within them, while prokaryotic cells lack these, usually containing DNA and a protein making structure called ribosomes. Actually, both eukaryotic and prokaryotic cells contain ribosomes, but eukaryotic cells have bigger ribosomes than prokaryotic cells do. As previously mentioned, eukaryotic cells contain organelles that help them function. The presence of these organelles help the eukaryotic cell perform more specific tasks that help the whole cell function more efficiently than a prokaryotic cell, which lacks these organelles. The most important organelle within a eukaryotic cell is the Nucleus, which helps to protect the DNA and control the rest of the cell. Since prokaryotic cells don’t have membrane-bound organelles, which includes the nucleus, their DNA is floating around the cytoplasm, the gel like substance that fills both prokaryotic and eukaryotic cells. Speaking of DNA, prokaryotic and eukaryotic cells contain differing DNA structures. In eukaryotic cells, there are multiple “chromosomes,” which are tightly compacted strings of linear DNA, contained in the nucleus. In prokaryotes, on the other hand, there is one, circular, piece of DNA. Since the DNA in prokaryotic and eukaryotic cells are stored differently, they also undergo different types of DNA replication. In prokaryotic cells, the reading of the DNA, called transcription, and the making of new DNA from that reading, called translation, are performed simultaneously in the cytoplasm. However, in eukaryotic cells, transcription and translation occur in separate places. Transcription happens in the Nucleus, where the DNA is stored. Then, the reading of the DNA, called RNA, goes into the cytoplasm, where the RNA is read and converted into new DNA that complements the original DNA. M.C. Question: Prokaryotic and eukaryotic cells both contain materials necessary for life. However, there are some key differences between the two. Which of the following are considered differences between prokaryotic and eukaryotic cells? I. Eukaryotic cells contain circular DNA, while prokaryotic cells contain linear DNA II. Prokaryotic cells are smaller than eukaryotic cells III. Prokaryotic cells have bigger ribosomes than eukaryotic cells A) I only B) II only C) I and II only D) I, II, and III Learning Log/FRQ-Style Question: Suppose that a scientist has two slides prepared for observation under the microscope. One slide contains a prokaryotic cell, and the other contains a eukaryotic cell. However, the scientist forgot to label the slides, and now he can’t remember which is which. Shown below are pictures of the two slides. a)Describe three differences between prokaryotic and eukaryotic cells b) Label the two slides as either prokaryotic or eukaryotic, and give at least two observations that led to your decision.

    14. Pictures for FRQ Question Slide A Slide B

    15. Answer Key – LO 2.14 M.C. Question: Prokaryotic and eukaryotic cells both contain materials necessary for life. However, there are some key differences between the two. Which of the following are considered differences between prokaryotic and eukaryotic cells? I. Eukaryotic cells contain circular DNA, while prokaryotic cells contain linear DNA II. Prokaryotic cells are smaller than eukaryotic cells III. Prokaryotic cells have bigger ribosomes than eukaryotic cells A) I only B) II only C) I and II only D) I, II, and III Learning Log/FRQ-Style Question: Suppose that a scientist has two slides prepared for observation under the microscope. One slide contains a prokaryotic cell, and the other contains a eukaryotic cell. However, the scientist forgot to label the slides, and now he can’t remember which is which. Shown below are pictures of the two slides. a) Describe three differences between prokaryotic and eukaryotic cells b) Label the two slides as either prokaryotic or eukaryotic, and Label the two slides as either prokaryotic or eukaryotic, and give at least two observations that led to your decision. • One difference between prokaryotic and eukaryotic cells are the size. Eukaryotic cells are bigger than prokaryotic cells are. This size difference is due to the fact that eukaryotic cells contain more than prokaryotic cells do. These contents are another difference between the two types of cells. Eukaryotic cells contains membrane-bound organelles, which are specialized structures that perform specialized functions within the cell and help the cell to function more efficiently. Prokaryotic cells do not contain these organelles. The third difference is the DNA within the two types of cells. In prokaryotic cells, the DNA is unbound, while in eukaryotic cells have a special organelle called the nucleus that functions as storage facility for the DNA, as well as the control center for the rest of the cell that the DNA functions from. • Slide A is the eukaryotic cell and Slide B is the prokaryotic cell. Slide A is the eukaryotic cell because it contains organelles, and the DNA is bound within a nucleus. Slide B is the prokaryotic cell because the DNA is unbound, and there are no organelles present.

    16. LO 2.29: The student can create representations and models to describe immune system responses. SP 1.1: The student can create representations and models of natural or man-made phenomena and systems in the domain. SP 1.2: The student can describe representations and models of natural or man-made phenomena and systems in the domain. Explanation: One of the many systems in our body is the immune system, a three level system of defense against pathogens such as viruses, bacteria, fungi, protists and other foreign/harmful substances that may enter our body. The body has two categories of immune defense: innate immunity, which is short term and attacks a broad range of antigens, and acquired immunity, which is long term and antigen-specific. Within the first line of defense there are external modes of defense such as barriers and traps as well as internal modes of defense such as unfavorable pH and lysosome enzymes. The second line of defense, though it doesn’t “remember” the pathogen, effectively rids the body of the harmful substances. Phagocytic white blood cells called leukocytes ingest pathogens and digest them with the help of lysosomes. The third line of defense, called acquired immunity, utilizes B cells and T cells (lymphocytes) and antibodies to attack and remember pathogens. When a pathogen gets past the first and second lines of defense, phagocytes engulf the pathogen and present MHC proteins on the outer surface of the cell membrane specific to the pathogen. Helper T cells then recognize the MHC proteins and “alert” the rest of the immune system by releasing cytokines. Cytotoxic T cells attack the Antigen presenting cell (APC) by releasing perforin into the cell causing it to undergo apoptosis while memory T cells are produced. Cytokines also signal fro plasma B cells and memory B cells. Plasma cells immediately produce antibodies as a rapid response. Memory B cells continually circulate in the body and provide long term immunity. All three of these lines of defense are necessary to quickly remove antigens from the body and prevent future attacks. MC Question: Which of the following statements concerning innate immunity is not true? A) The pH of stomach acid causes pathogens to denature B) Anitbodies received from breast feeding are part of innate immunity C) Innate immunity comes from structures we’re born with D) Sneezing and coughing are modes of elimination FRQ Question: What is the difference between innate and acquired immunity? Give examples of both. Active and passive immunity? Give examples of both.

    17. Answer Key LO 2.29 MC Question: Which of the following statements concerning innate immunity is not true? A) The pH of stomach acid causes pathogens to denature B) Anitbodies received from breast feeding are part of innate immunity C) Innate immunity comes from structures we’re born with D) Sneezing and coughing are modes of elimination FRQ Question: What is the difference between innate and acquired immunity? Give examples of both. Active and passive immunity? Give examples of both. How do these differences affect the body in short term and long term circumstances? Innate immunity is comprised of the first two lines of defense and has only short term results. These modes of defense, including the skin and mucous membranes as well as leukocytes and natural killer cells, attack a very broad spectrum of antigens and rid the body of them very quickly. Acquired immunity is the third line of defense and allows the body to “remember” and recognize antigens it has already fought off. This line of defense attacks the antigen and produces memory T cells to prevent further attacks. Cytotoxic T cells and antigen presenting cells (APCs) are both part of this line of defense. Acquired immunity has two types of defense. Active defense is when antibodies and memory T cells are produced through the forming of an APC when the body is attacked by a certain antigen. Passive defense is when the body is not infected with the antigen but receives the antibodies from an outside source such as vaccinations or breast feeding.

    18. LO 2.38: The student is able to analyze data to support the claim that responses to information and communication of information affect natural selection. SP 5.1: The student can analyze data to identify patterns or relationships. Explanation: Natural selection (reproduction of the fittest) is a response to things like environmental changes and mutations in specific members of a population. Plants are the best example for this LO. If the entire plant isn’t exposed to the same kind of light all around and for the same amount of time, then some leaves will grow larger and survive longer than the smaller leaves because they have a larger surface area to do photosynthesis (they can absorb more light than the smaller leaves). We can observe this with a graph showing the results of having a plant exposed to different wavelengths of light and their resulting light absorption (the higher the light absorption, the higher the photosynthetic rate). In this well-known experiment by Thomas Engelmann, it was proven that photosynthesis happens best under blue-purple light and red-orange light. This is because oxygen-using bacteria will migrate to places where a lot of oxygen is released because of photosynthesis. We have to know how to analyze the graph to reach these conclusions. By observing that the white line is the highest around 400-425 nm and 650-675 nm, we can come to a conclusion that the chlorophyll absorption spectrum of visible light is the most efficient under blue-purple and red-orange light. This supports the LO because the data analyzed proves that a response to information (wavelength) affects natural selection (the plants exposed to the more efficient wavelength will do photosynthesis faster and more efficiently and thus survive longer). M.C. Question: According to the graph on the right, chlorophyll absorbs the most light under which wavelength(s) of light? 500 nm 700 nm 425 nm 675 nm Both C and D Learning Log/FRQ-style Question: A researcher is doing an experiment on algae to see what kind of wavelength of light encourages photosynthesis the most efficiently. She grows algae in front of a prism of light to expose different areas to different wavelengths. Using the graph on the right to help you, predict what the her results will be, and explain why the results are the way they are.

    19. ANSWER KEY – LO 2.38 According to the graph on the right, chlorophyll absorbs the most light under which wavelength(s) of light? 500 nm 700 nm 425 nm 675 nm Both C and D (correct answer) A researcher is doing an experiment on algae to see what kind of wavelength of light encourages photosynthesis the most efficiently. She grows algae in front of a prism of light to expose different areas to different wavelengths. Using the graph on the right to help you, predict what her results will be, and explain why the results are the way they are. The scientist will reach the results that chlorophyll will absorb light the best, and therefore do photosynthesis the most efficiently, under the purple-blue light (425 nm). This is because this wavelength of light can release lots of oxygen during photosynthesis (because the absorption is so high), so the oxygen-using bacteria will travel to the area that has the most oxygen to use. Algae will grow the best and the fastest under this light. On the flip side, the algae under the green light (525 nm) will hardly grow at all. Chlorophyll can’t absorb green light, which is why leaves (or algae in this case) appear to be green in the first place. Since the chlorophyll can’t absorb the green light, there’s no starting place for photosynthesis and it just won’t happen.

    20. LO 3.21- The Student can use representations to describe how gene regulation influences cell products and functions. SP 1.4 The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Explanation- Brain and kidney cells each contain DNA but their functions are vastly different. This is due to gene regulation, which turns “on” and “off” certain genes, this effects the expression of the genes in the cell and influences the cell products and the overall function of the cell. Gene regulation happens at many different levels, for example the DNA level or the RNA level. At the DNA level, for example, there is DNA methylation, which is a turn of switch that puts caps on sections of DNA with methyl groups and Histoneacetylation, which is an on switch that unwinds DNA for easier translation. At the RNA level there is the activation of transcription with proximal and distal control elements and enhancers and silencers. All the regulators at the RNA level effect transcription. In eukaryotes, the control of transcription depends on the binding of activators to DNA control elements. For example before the start of transcription an activator protein binds to the distal control element which forms a enhancer (activator). The a DNA-bending protein then bends the DNA and helps it connect to general transcription factors at the TATA/Promoter region of the strand. This will eventually initiate RNA synthesis. The different combinations of control elements affects what genes are expressed on the strand of new RNA. After the mRNA is processed and is translated by a ribosome the protein is formed it will be sent off to do work. These different gene regulators, regulate what genes are expressed which when translated makes many different kind of proteins. This allows brain cells and kidney cells, which both contain the same genome, to have very different functions and produce different things that the body needs. For example a kidney cell will the enzyme Calcitriol, while the brain cell will produce neurotransmitters. M.C. Question – Which of the following regulator of gene expression occurs at the DNA level? A) DNA methylation turns off a switch for sections of RNA and puts caps on the RNA with methyl groups which is a key process in regulation of gene expression. B) Proximal and distal elements bind upstream from the promoter, effect the gene expression. C) DNA creates a protein that is degraded because it is tagged by ubiquiden to be engulfed by Protosomes. D) Enzymes called histoneacetelyation, acetylate lysine amino acids on histone proteins by transferring an acetyl group from acetyl CoA to form N-acetyl lysine as a important part of gene expression. Learning Log/FRQ Style Questions Both liver cells and lens cells have the genes to make the proteins albumin and crystallin, but only liver cells make albumin (a blood protein) and only lens cells make crystallin. This is possible through transcription factors. Describe the process and influence of activator and repressor proteins on the DNA which allows for liver and lens cells to make different proteins.

    21. M.C. Question Answer – Which of the following regulator of gene expression occurs at the DNA level? A) DNA methylation turns off a switch for sections of RNA and puts caps on the RNA with methyle groups which is a key process in regulation of gene expression. B) Proximal and distal elements bind upstream from the promoter, effect the gene expression. C) DNA creates a protein that is degraded because it is tagged by ubiquiden to be engulfed by Protosomes. D) Enzymes called histoneacetelyation, acetylate lysine amino acids on histone proteins by transferring an acetyl group from acetyl CoA to form N-acetyl lysine as a important part of gene expression. Learning Log/FRQ Style Questions- Answer Both liver cells and lens cells have the genes to make the proteins albumin and crystallin, but only liver cells make albumin (a blood protein) and only lens cells make crystallin. This is possible through transcription factors. Describe the process and influence of activator and repressor proteins on the DNA which allows for liver and lens cells to make different proteins. Transcription factors allow for gene’s to express different traits. Enhancers, or activators proteins, bind to distal control elements which form an enhancer on the DNA. This enhancer has three binding sites. Then a DNA bending protein brings the bound activators closer to the promoter. The activators then bind to general transcription factors and mediator proteins which affect transcription initiation at the promoter site. The promoter site includes the TATA box. The liver cell and lens cells have different types of activators and repressors which allows for creation of two very different proteins. These proteins allow for different cell functions. By: Gracie Nicklas-Morris

    22. LO 2.32: The student is able to use a graph or diagram to analyze situations or solve problems that involve timing and coordination of events necessary for normal development in on organism. SP 1.4: The student can use representations and models to analyze situations or solve problems qualitatively and quantitatively. Explanation: Fruit flies, for example, are good model organisms because they share key developmental life cycle events with humans. Their egg cells develop within the female ovaries, surrounded by ovarian cells called nurse cells and follicle cells. The egg cell is able to develop and is fertilized within the mother and then laid. The first ten mitotic divisions have 2 notable features: they consist of S and M phases, with no growth, so the amount of cytoplasm does not change, and cytokinesis does not occur, so the embryo is one of big multinucleate cells. At the tenth nuclear division, the nuclei begin to migrate, forming and early blastula-like stage called blastoderm. At division 13, plasma membranes finally partition the nuclei into separate cells. A centrally placed yolk nourishes the embryo, and the egg shell continues to protect it. Clearly visible segments of the embryo form. Then, some cells move to new positions, and organs form. The fly may now develop into its adult form. M.C. Question: The criteria for a good model organism for studying development would probably include all of the following except: A- observable embryonic development B- short generation time C- a relatively small genome D- preexisting knowledge of the organism’s life history E- a rare pattern of development when compared to most organisms Learning Log/FRQ-style Question: The DNA sequences called homeoboxes, which help homeotic genes in animals direct development, are common to flies and mice. Given this similarity, explain why these animals are so different.

    23. ANSWER KEY – LO 2.32 M.C. Question: The answer is E- a rare pattern of development when compared to most organisms. Learning Log/FRQ Style Question: Homeotic genes differ in their homeotic sequences, which determine their interactions with other transcription factors and which genes are regulated by the homeotic genes. These interactions differ in the two organisms, as do the expression patters of the homeotic genes. The expression patterns are regulated on the DNA level by DNA methylation and histone acetylation. DNA methylation turns off a gene by capping it with a methyl group. Histone acetylation attaches actely groups (-COCH3) to positively charged lysines in histone tails. When histone tails are acetylated, their positive charges are neutralized and they no longer bind to neighboring nucleosomes. This “unwinds” DNA for an easy transcription.

    24. LO 1.16: The student is able to justify the scientific claim that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. SP 6.1: The student can justify claims with evidence. Explanation: All life on Earth is related and can be traced back through lines of descent to a common ancestor. Organisms inherit traits from their parents, and their parents from their parents. The traits are and have been passed down through the genes over and over with occasional mutations, allowing for extreme differences and similarities between the ancestor and current organisms. All organisms have DNA and/or RNA, a universal genetic code with which they carry their genetic information and pass it on through transcription, translation, and replication. Major features of the genetic code, such as the nucleotide bases A, T/U, C, and G, are shared by all modern living systems. Metabolic pathways, as well, are conserved across all domains of life; for example, glycolysis of respiration is performed by all organisms and structural evidence supports the relatedness of all eukaryotes. Lost and acquired traits can be represented in phylogenetic trees, branching diagrams that graphically model evolutionary history based on similarities and differences in genetic and physical characteristics. M.C. Question: Based on information provided in the diagram directly below, which two organisms are most closely related to one another? A) Chordata and Anthropoda B) Tardigrada and Nematoda C) Kinorhyncha and Annelidia D) Mollusca and Entoprocta Learning Log/FRQ-style Question: Compare and contrast a basic eukaryotic cell and a basic prokaryotic cell. Identify similar processes and features and explain why they can be present in the different types of cells.

    25. Answer Key – LO 1.16 Based on information provided in the diagram directly below, which two organisms are most closely related to one another? A) Chordata and Anthropoda B) Tardigrada and Nematoda C) Kinorhyncha and AnnelidiaD) Mollusca and Entoprocta Learning Log/FRQ-style Question: Compare and contrast a basic eukaryotic cell and a basic prokaryotic cell. Identify similar processes and features and explain why they can be present in the different types of cells. A cell is the basic unit of life as according to cell theory and all cells are either eukaryotic or prokaryotic. Prokaryotic cells are cells lacking a membrane-bound nucleus or any other membrane-bound organelles. Prokaryotes generally always have a cell wall and are unicellular organisms. Eukaryotic cells are cells that contain a nucleus and membrane-bound organelles. All multicellular organisms, such as plants, animals, and fungi, are eukaryotes, though eukaryotes can also include unicellular organisms as well, such as protozoa. Eukaryotes and prokaryotes both have DNA as their genetic material and are both membrane bound, though eukaryotes contain their DNA in the nucleus where prokaryotes have DNA that floats freely around the cell. Eukaryotic DNA is much more complex than prokaryotic DNA and therefore much more extensive. The two cells reproduce in different ways, the prokaryotes dividing asexually by binary fission, or simple cell division, and eukaryotes dividing by mitosis and can also do sexual reproduction. Eukaryotes originally came from prokaryotes in a process called endosymbiosis. A large prokaryote engulfed a much smaller aerobically respiring one through endocytosis. Because of this,both cells are similar in their metabolisms and in the way they produce energy. Eukaryotes are generally about ten times larger than prokaryotes and have organelles, such as mitochondria, that produce energy for them that have evolved from the engulfed from the smaller aerobic prokaryote.

    26. LO 1.24: The student is able to describe speciation in an isolated population and connect it to change in gene frequency, change in environment, natural selection and/or genetic drift.SP 7.2: The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understanding and/or big ideas M.C. Question: Which of the following would result in the greatest change in an isolated population of humans? A) a large number of babies were recently born into the population B) a widespread disease struck the populationC) a major earthquake occurredD) many species of birds were hunted Explanation: An isolated population will often reach the state of equilibrium, where evolution is not occurring. This will only happen if the population is also large, if no mutations occur, if all mating is random, and if no natural selection is present. If any of these requirements are not met, the population will change through a microevolution. Small populations are more susceptible to random changes and can easily result in genetic drift, where the changes develop into a major alteration in the population. For example, one of the most common types of genetic drift is the bottleneck effect, where a small population's gene pool is affected by a disaster (the random change), and the remaining population must inbreed to repopulate. Another method of change in gene frequency is gene flow, where emigration and/or immigration involves in the gain or loss of alleles and the remaining population undergoes a microevolution since it was so longer isolated. Mutations often result in a favorable trait being developed, which would help a mutated individual and the individual would outcompete others in the population. Natural selection will allow the mutant to survive and successfully reproduce, passing on its favorable trait(s). The allelic frequency of this gene will increase, because it is recognized as favorable, and in time the majority of the population will have evolved (sometimes to a new species) to have this gene. • FRQ Question: Suppose an island population is cut off from the mainland. The island is prone to widely varying weather which can include raging storms , unbearable heat, and the occasional bout of snow if it gets cold enough. • Explain what effect that weather has on the population size. Hypothesize what could happen to the population’s gene pool and allelicfrequency if it were to hail for an entire year. • Hypothesize what could happen if an invading species entered the isolated population. Include an immediate effect and a long-term effect. An example graph of competition for food

    27. ANSWER KEY– LO 1.24 Which of the following would result in the greatest change in a population of humans that is in equilibrium? A) a large number of babies were recently born into the population; this would just add to the population size, and it is assumed that the death rate will counter the birth rate.B) a widespread disease struck the population; one of the most common disadvantages to a dense population is the easy spread of disease, which regulates the large populations back below carrying capacity (understanding of a population in equilibrium is required to infer that the population in question is in fact a large population).C) an earthquake occurred; while it could possibly result in many deaths, it is not a major earthquake, and its effect would most likely be an immediate and then a short-term one.D) many species of birds were hunted; though excessive hunting could lead to threatening of species, this answer only says that many different species were hunted, so the hunting of birds really only mimics predators preying on birds, which is normal. Suppose an island population is cut off from the mainland. The island is prone to widely varying weather which can include raging storms, unbearable heat, and the occasional bout of snow if it gets cold enough. a) Hypothesize what could happen to the population’s gene pool and allelic frequency if it were to hail for an entire year. b) Hypothesize what could happen if an invading species entered the isolated population. Include an immediate effect and a long-term effect. Exposure to extremely cold weather can kill just about any land animal that has not adapted to it. Considering how the weather is known tofluctuate in the population, it is logical to assume that the organisms have adapted to rapidly changing weather, but they are unfamiliar witha sustained climate. Due to this, the isolated population will be likely to suffer many deaths from lack of food, overexposure to cold, etc. Aftermany organisms have died, the remaining population will be forced to repopulate. At this point, the gene pool has been drastically reduced bythe loss of victims of the hail season. The repopulation will show a bottleneck effect, and the small gene pool will force the population to begininbreeding, and the specific alleles that the remaining individuals have will become very prominent in the population (since those alleles are theonly ones left). An immediate effect of the presence of an invading species is that it would be likely to compete with an indigenous species, or it could fill a new niche in the population and not have to compete with another species. However, should the invading species compete with the indigenousspecies, the invading one could easily win if it has a favorable trait from outside the isolated population’s gene pool. Should this be the case, the two species would continuously compete until eventually the invading species outcompetes the indigenous species. The long-term effect here is that the indigenous species was replaced and it either migrated elsewhere or became extinct.

    28. a) LO 3.35 The student is able to create representation(s) that depict how cell-to-cell communication occurs by direct contact or from a distance through chemical signaling. [See SP 1.1] b) SP 1.1 The student can create representations and models of natural or man-made phenomena and systems in the domain c) Explanation: Cell signaling can be divided into two subcategories. Paracrine signaling is from one cell to another in close range. It is a signal that is secreted into the extracellular fluid by a nearby cell and causes a differentiation of cells in close range after reception of the recognized signal. An example of paracrine signaling occurs during embryonic development. In developing embryos, stem cells are differentiated through this process. The forth cell of the embryo releases a signal to tell the half of cell three closest to cell four to activate the genes responsible for intestinal cells. Endocrine signaling is long distance signaling involving hormones and steroids. There are three stages: 1) Reception- ligand (signal molecule) binds to a receptor protein that causes a transduction pathway. 2) Transduction- conversion of the received signal to a specific cellular response. According to the science practice 1.1, a model of how transduction occurs in the 4 types of transduction pathways is necessary. 3) Response- cell responds to signal. There are 4 different types of endocrine receptors: 1) Intracellular receptors- steroid hormone receptors. These receptors are found within the cytoplasm. Small polar substances, like steroids, can pass easily through the cell membrane. This creates a more direct transcriptional change. 2) G- protein linked receptors- the ligand causes a change in receptor shape which attracts the inactive G-protein. Through the action of GTPase, GTP displaces GDP through hydrolysis, activating the G-protein. The active G-protein can then activate other specific molecules. 3) Tyrosine Kinase receptors- when the ligand binds, the receptor forms a dimer (two part structure). The tyrosine aa of the dimer is phosphorylated by the hydrolysis of ATP and this activates the relay proteins. 4) Ligand gated ion channels- when the ligand binds, a change in shape occurs and specific ions can move down the concentration gradient. An example would be neurotransmitters at the synapse of a neuron. Second messengers are another important part of endocrine signaling. 1) cAMP (cyclic AMP)- adenylyl cyclase converts ATP to cAMP. After a G-protein is activated, it activates the adenylyl cyclase. With the use of ATP, cAMP is formed. The cAMP then activates a protein kinase and an eventual cellular response. 2) IP3- second messenger that are releases Ca2+ from the endoplasmic reticulum. This happens every time a muscle contracts and during cell division. After a G-protein is activated and activates a relay protein, PIP3 (which is attached to the cellular membrane) is broken off into two parts. DAG stays in the membrane, and IP3 acts as a second messenger that travels to the ER to release the gated calcium channels. When PIP3 attaches to the channels, a shape change occurs and the calcium ions are released. The Ca2+ ions can also act as second messengers to activate various proteins and result in a cellular response. Signal amplification occurs when a single ligand activates millions of molecules during a cell response. The reason for all of the steps in the pathway is to cause an amplified response. Different responses to the same cell occur because of different relay proteins, and different receptor types. Scaffolding proteins can make this response even quicker by binding several different molecules together. It also brings proteins together so they can interact. Multiple Choice Question: A glucocorticoid is released from the adrenal cortex and must be received by the target cells. Which of the following receptors is most likely to receive the signal? G-protein linked receptor Intracellular receptor Tyrosine kinase receptor Ligand-gated ion channel Free Response Question: cAMP is a second messenger that is synthesized via a transduction pathway. Describe the process that leads to the production of cAMP and how cAMP causes a final cellular response. Explain the function of second messengers and describe one additional example of a second messenger in transduction pathways. Include with your answer a labeled diagram of the cAMP transduction pathway.

    29. Answer Key Multiple Choice Question: A glucocorticoid is released from the adrenal cortex and must be received by the target cells. Which of the following receptors is most likely to receive the signal? • G-protein linked receptor • Intracellular receptor • Tyrosine kinase receptor • Ligand-gated ion channel Explanation: The endocrine glands of the body release steroids, a specific type of hormone. The adrenal cortex is an endocrine gland and glucocorticoids are steroids that are responsible for regulating metabolism, inflammation, and for calming the body. Because steroids are small, polar substances, they can diffuse easily through the cell membrane. They then bind to an intracellular receptor that makes a direct transcriptional change. Free Response Question: cAMP is a second messenger that is synthesized via a transduction pathway. Describe the process that leads to the production of cAMP and how cAMP causes a final cellular response. Explain the function of second messengers and describe one additional example of a second messenger in transduction pathways. Include with your answer a labeled diagram of the cAMP transduction pathway. Explanation: A ligand, or signal molecule, binds to the g-protein linked receptor on the cell membrane. A G-protein is then activated with GTP. The G-protein then activates adenylyl cyclase. Adenylyl cyclase uses ATP to make cAMP. cAMP then acts as a second messenger in the pathway. cAMP is phosphorylated by protein kinases and a cellular response is initiated. Second messengers function as a way to amplify a cellular response. This can be seen when a G-protein pathway activates a relay protein that cleaves IP3 off of the PIP2 molecule. IP3 acts as a second messenger and travels to the endoplasmic reticulum which holds Ca2+ ions. When it binds to the membrane of the ER, the shape change causes the Ca2+ ions to be released and initiate cellular responses.

    30. LO 2.20: The student is able to justify that positive feedback mechanisms amplify responses in organisms. SP 6.1: The student can justify claims with evidence. Explanation: Positive feedback involves a change in some variables that trigger mechanisms that amplify rather than reverse the change. For instance, in childbirth, the pressure of the baby’s head against receptors near the opening of the uterus stimulates uterine contractions, which cause greater pressure against the uterine opening, heightening the contractions, which causes still greater pressure. Another good example of a positive feedback mechanism is blood clotting. Once a vessel is damaged, platelets start to cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed. M.C. Question: Ethylene, a plant hormone, plays what part in fruit development? A) It stimulates the ripening of unripe fruit. B) It allows for the fruit to begin its reproduction process. C) It causes the fruit to emit a pleasant fragrance that attracts animals to consume it. D) It allows the plant to uptake water through the root hairs which provides fruit with an energy source. Learning Log/FRQ-style Question: Explain how lactation in mammals is the result of a positive feedback response.

    31. ANSWER KEY- LO 2.20 Ethylene, a plant hormone, plays what part in fruit development? A) It stimulates the ripening of unripe fruit. B) It allows for the fruit to begin its reproduction process. C) It causes the fruit to emit a pleasant fragrance that attracts animals to consume it. D) It allows the plant to uptake water through the root hairs which provides fruit with an energy source. Explain how lactation in mammals is the result of a positive feedback response. A baby begins to suckle it’s mother’s nipple or teat and a few drops of milk are released. This acts as the stimulus. The milk releases encourages the baby and releases a hormone known as oxytocin in the mother, which further stimulates the release of milk. This is the response to the stimulus. As the baby continues to suckle, more milk is stimulated to be released by the mother. More stimulus results in more and greater of a response.

    32. LO 2.36 The student is able to justify scientific claims with evidence to show how timing and coordination of physiological events involve regulation.SP 6.1 The student can justify claims with evidence. MC Question: A deer running from the sight of a wolf is an example of: An olfactory response Taxis Classical conditioning Kinesis Imprinting The student should connect specific physiological responses that plants, animals, and fungi/protists/bacteria have to internal and external (environmental) stimuli. - In plants, phototropism is the process where a plant will grow (response) towards sunlight (stimulus). - In animals, hibernation (response) is regulated by seasonal changes in temperature (stimulus). - In bacteria, quorum-sensing coordinates transcription (response) within colonies of bacteria when the density of the colony has reached a threshold (stimulus). • FRQ: Of the following, choose two and describe how they involve the relationship between stimulus and response. Be sure to include an example for each. • Cell differentiation • Behavioral conditioning • Action potentials in neurons Phototropism

    33. Creating an Action Potential Answers LO 2.36 MC Question: A deer running from the sight of a wolf is an example of: An olfactory response Taxis – movement toward or away from stimulus Classical conditioning Kinesis Imprinting Stem cells become differentiated, or made specific, during induction within an embryo; signal molecules are released from an embryonic cell, beginning with a 4-cell embryo, and those molecules turn on a regulatory gene in a different cell which begins the transcription of proteins to make the cell differentiated. One example is the vulva formation of nematodes where an anchor cell releases signals onto the epidermis; the cells that receive the most molecules turn into the vulva. Behavioral conditioning includes both classical and operant conditioning. Classical conditioning is involuntary behavioral change that occurs when a stimulus is paired with a different desirable or undesirable stimulus to cause them to be associated together; Pavlov’s dogs were trained to salivate at the sound of a bell because they became used to hearing the bell before receiving food. Operant conditioning involves voluntary behavior where the subject, such as a bird, must perform a behavior to get a reward or avoid punishment, like pecking at a button to receive feed. An action potential is created when the amount of excitatory signals (EPSPs) overpowers the amount of inhibitory signals (IPSPs) received by a neuron; the neuron must leave its resting potential of -70mV and must pass the threshold of -55mV to fire. For example, if a neuron in the brain receives a rapid amount of epinephrine, the body will begin the fight-or-flight response as more and more neurons respond by releasing the same neurotransmitter.

    34. LO 3.22 The Student is able to explain how signal pathways mediate gene expression, including how this process can effect protein production. SP 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Explanation: Cell signaling starts with signal reception, signal transduction, and cellular response. Signal molecules (ligands) bind to specific sites on receptor proteins (G-protein-linked receptor, receptor tyrosine kinases, or ion channel receptor) embedded in the plasma membrane, which activates it. Receptors transmit information when a specific ligand binds to it. Transduction is a multistep pathway where the receptor triggers a relay protein, which begins the phosphorylation cascade (where different molecules in a pathway are phosphorylatedin turn, each molecule adding a phosphate group to the next one in line). Once phosphorylated the last kinase in the sequence enters the nucleus and there activates a gene-regulating protein, a transcription factor. This protein stimulates a specific gene so than an mRNA is synthesized (transcription). The mRNA is used by ribosomes in the cytoplasm to synthesize proteins (translation). In other words, different activator proteins are present in different cells and activate different genes to synthesize different proteins that cause differences in cell type, structure and/or behavior, and therefore gene expression. M.C. Question: Which of the following is not an example of signal molecules mediating gene expression? • Epinephrine regulating cell metabolism • Cytokines regulating cell replication and division • Ethylene regulating fruit ripeness • Chaperonins regulating sugar synthesis • Testosterone regulating male sex characteristics Learning Log/FRQ-style Question Prolactin is a hormone that initiates breasts to produce milk. Briefly explain each step involved in cell signaling in terms of the diagram and the example given to show how signal pathways mediate gene expression. (Cues: signal molecule, receptor, transduction, phosphorylation cascade, response, mRNA, transcription, translation)

    35. ANSWER KEY-LO 3.22 Which of the following is not an example of signal molecules mediating gene expression? • Epinephrine regulating cell metabolism • Cytokines regulating cell replication and division • Ethylene regulating fruit ripeness • Chaperonins regulating sugar synthesis • Testosterone regulating male sex characteristics Prolactin is a hormone that initiates breasts to produce milk. Briefly explain each step involved in cell signaling in terms of the diagram and the example given to show how signal pathways mediate gene expression. (Cues: signal molecule, receptor, transduction, phosphorylation cascade, response, mRNA, transcription, translation) Reception In this pathway the prolactin is the signal molecule and it binds to a receptor protein. When the signal protein binds, the receptor protein initiates transduction by triggering a relay molecule and leads to the phosphorylation cascade. Once phosphorylated the last kinase in the sequence enters the nucleus where the response to the signal takes place and causes a change in gene expression. The activated gene-regulating protein(transcription factor) causes a gene to be activated, in this case the gene that stimulates breast milk synthesis. The stimulation of a specific gene causes mRNA to be synthesized from the DNA through transcription. The mRNA is used by ribosomes in the cytoplasm to synthesize milk proteins through translation. The presence of prolactin lead to the milk production gene being expressed by producing milk proteins that led to milk production. Transduction Response

    36. LO 3.9 The student is able to construct an explanation, using visual representations or narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis, or meiosis followed by fertilization. SP 6.2 The student can construct explanations of phenomena based on evidence produced through scientific practices. Explanation: Meiosis is preceded by the replication of chromosomes in a similar fashion as what takes place during mitosis, but this one replication is followed by two cell divisions called meiosis I and meiosis II. During meiosis I crossing over takes place so that DNA molecules in nonsister chromatids break at corresponding places so that they can rejoin the other DNA in order to create DNA variation. The results of these two divisions is the creation of four daughter cells rather than the two daughter cells from mitosis. These four daughter cells are unique because they have half as many chromosomes (haploid) as the parent cell. It is very important to recognize that the cells only have half the amount of chromosomes because this allows for the cell to become fertilized so that chromosomes from the female and chromosomes from the male so that the cell can become diploid. After the gamete becomes fertilized the new diploid cell can begin the process of mitosis. By beginning the process of mitosis the fertilized cell is able to continue replicating its DNA so that an embryo can begin to form because the process of mitosis makes exact clones of the cell being replicated. Multiple Choice Question: Arrange the following five events in the order that explains how genetic variation takes place during meiosis. Nonsister chromatids break at corresponding locations due to crossing over Homologous chromosomes pair loosely Chromosomes replicate to make to genetically identical sister chromatids Tetrads are formed and line up along the Metaphase plate 5. Microtubules attach to each homologue a) 1,3,4,2,5 b) 2,3,1,4,5 c) 3,2,1,5,4 d) 5,4,1,3,2 e) 3,2,4,1,5 Free Response Question: Why is it necessary for fertilization that a cell undergo meiosis in order to create four haploid gamete cells? Describehow meiosis makes four haploid gamete cells and explain why after fertilization a cell switches from using meiosis to mitosis. Model of Mitosis (left) and Meiosis (right)

    37. Multiple Choice Question: Arrange the following five events in the order that explains how genetic variation takes place during meiosis. Nonsister chromatids break at corresponding locations due to crossing over Homologous chromosomes pair loosely Chromosomes replicate to make to genetically identical sister chromatids Tetrads are formed and line up along the Metaphase plate 5. Microtubules attach to each homologue a) 1,3,4,2,5 b) 2,3,1,4,5 c) 3,2,1,5,4 d) 5,4,1,3,2 e) 3,2,4,1,5 Free Response Question: Why is it necessary for fertilization that a cell undergo meiosis in order to create four haploid gamete cells? Describe how meiosis makes four haploid gamete cells and explain why after fertilization a cell switches from using meiosis to mitosis. It is necessary for a cell to undergo meiosis in order to successfully go through fertilization. Meiosis creates four haploid game cells that have half of the total chromosomes as the parent cell. The Chromosomes are replicated during interphase which creates two genetically identical sister chromatids. The during prophase I the homologous chromosomes are loosely paired so that crossing over may take place. Crossing over is when the DNS molecules in nonsister chromatids break at the same location and then rejoin to the opposite chromatid. This process creates DNA variation from the parent cell. After crossing over is completed tetrads (a group of four chromatids) are formed and they line up along the Metaphase plate. During metaphase I both chromatids are attached to microtubules from one pole or the other. During anaphase I the chromosomes move towards the poles where they will remain attached at the centromere. At the very beginning of telophase I each half of the cell has a complete set of haploid chromosomes until cytokinesis takes place. Cytokinesis is the division of the cytoplasm so that two haploid cells are created. This completes meiosis I so that meiosis II may begin. All of the steps from meiosis I are repeated during meiosis II except for crossing over. Once cytokinesis takes place for the second time the final result will be four haploid, genetically unique cells. It is important that meiosis creates four haploid cells so that when the cells are fertilized by the haploid gametes of the opposite gender the two gametes’ chromosomes can combine to create a diploid cell. Once the original haploid gamete becomes fertilized then mitosis takes place. During mitosis the cell is duplicated to create two genetically identical daughter cells to the parent cell. This is important because the process of mitosis helps to create enough genetically identical cells so that an embryo may begin to form.

    38. LO 1.28: The student is able to evaluate scientific questions based on hypotheses about the origin of life on Earth. SP 3.3: The student can evaluate scientific questions. Explanation: Oparin and Haldane hypothesized that Earth’s early atmosphere had been a reducing environment. This would have allowed for simple molecules to become organic compounds with the energy from lightening or UV radiation. Experiments simulating early earth produced all the monomers, amino acids, and purines and pyrimidines. Researchers also believe that some organic compounds could have come from outer space in meteorites. Researchers have been able to make polymers by dripping amino acids onto hot sand, clay, or rock. Nucleotides are believed to have been created with the help of protobiont which can form from abiotically produced organic compounds. There are still questions about the composition of early Earth’s atmosphere and if it actually was reducing. Multiple Choice Question: What aspect of early Earth’s atmosphere aided the most in the formation of organic compounds? a)The existence of amino acids b)The environment was electron adding c)The lack of water d)The large amount of red light Free Response Question: Explain one hypothesis about how the Earth was formed Describe in detail an experiment that could be used to support the hypothesis. c) Give one possible source of error in the experiment described above.

    39. L.O. 1.28 Answer Key What aspect of early Earth’s atmosphere aided the most in the formation of organic compounds? a)The existence of amino acids b) The electron adding environment c) The lack of water d)The large amount of red light Free Response Question: Explain one hypothesis about how life on Earth was formed Describe in detail an experiment that could be used to support the hypothesis. Give one possible source of error in the experiment described above. One hypothesis of how life formed on early earth is that the reducing environment allowed for simple molecules to form organic compounds with the energy from lightening. Miller and Urey tested this hypothesis in an apparatus they built to simulate conditions on early earth. The reducing atmosphere was created with hydrogen, methane, ammonia, and water vapor. The sea was simulated by a flask of warmed water. Lightening was simulated by sparks from an electrode. The atmosphere was cooled by a condenser and water and any compounds fell into the “sea”. The experiment produced many organic molecules, including amino acids, sugars, lipids, purines, pyrimidines, ATP, and all monomers. One possible error is that researchers do not know the exact conditions of the early atmosphere. There may not have been enough methane and ammonia to be reducing.

    40. Learning Objective 2.13 – The student is able to explain how internal membranes and organelles contribute to cell functions. Science Practice 6.2 – The student can construct explanations of phenomena based on evidence produced through scientific practices. Explanation – The internal membranes and organelles contribute to the function of the cells in many different, but very specific and individual, ways. For example, the Golgi Apparatus’ main role is to manufacture, store, sort, and ship everything that comes through the cell. The Vesicles carry materials to the Golgi for sorting, and they also carry other materials to the plasma membrane. Another organelle, known as the Lysosome, is responsible for the carrying out the process of hydrolysis to break down old cell parts. The two most important organelles of a cell are the Mitochondria and Chloroplasts cell. The Mitochondria is the site of aerobic respiration, during which three stages occur: 1. Glycolysis, 2. Krebs Cycle, and 3. Oxidative Phosphorylation. Aerobic respiration is a form of cellular respiration that requires oxygen in order to generate energy. The Chloroplasts are responsible for the process of photosynthesis in plants and other Prokaryotes only. Of these two important organelles are very important internal membranes, the mitochondrial membrane and the thylakoid membrane, which also contribute to the cell’s function in a unique and important way. The thylakoid membrane of a chloroplast is an elaborate system of interconnected membrane sacs that segregates the stroma from the thylakoid space. Within the Thylakoid Membrane resides chlorophyll, which is needed to absorb sunlight. The Mitochondrial Membrane of the mitochondria is responsible for the Electron Transport Chain (ETC) and Chemiosmosis. The purpose of the ETC process is harvesting the energy of reduced coenzymes NADH and FADH2, which are formed in Glycolysis and the Krebs Cycle. The purpose of Chemiosmosis is to create an influx of ATP. There is and will always be a strong relationship between an internal membrane and/or an organelle and the cell’s function. Multiple Choice Question: What is the difference between the Rough Endoplasmic Reticulum and the Smooth Endoplasmic Reticulum? The Rough ER is used to transport materials, as the Smooth ER is used to store them. The Smooth ER stores Ca +2 while the Rough ER makes membrane components. The Smooth ER carry out hydrolysis, and the Rough ER carries out dehydration synthesis. The Rough ER ships glycoproteins, and the Smooth ER detoxifies lipids. Free Response Question: Organelles and internal membranes play important roles in a cell, as they contribute to their function. Since you know this information, answer the following questions related to organelles and internal membranes. What are the building blocks of the endomembrane system? What are THREE of their functions? What does TWO of these building blocks create? Give ONE example of an internal membrane of your choice and describe its function and purpose. What happens if this particular process stops?

    41. ANSWER KEY – Learning Objective 2.13 What is the difference between the Rough Endoplasmic Reticulum and the Smooth Endoplasmic Reticulum? The Rough ER is used to transport materials, as the Smooth ER is used to store them. The Smooth ER stores Ca +2 while the Rough ER makes membrane components. The Smooth ER carry out hydrolysis, and the Rough ER carries out dehydration synthesis. The Rough ER ships glycoproteins, and the Smooth ER detoxifies lipids. Organelles and internal membranes play important roles in a cell, as they contribute to their function. Since you know this information, answer the following questions related to organelles and internal membranes. What are the building blocks of the endomembrane system? What are THREE of their functions? What does TWO of these building blocks create? Give ONE example of an internal membrane of your choice and describe its function and purpose. What happens if this particular process stops? The building blocks of the endomembrane system are the nuclear envelope, rough endoplasmic reticulum, golgi apparatus, smooth endoplasmic reticulum, lysosomes, vacuoles, and the plasma membrane. The nuclear envelope surrounds the nucleus and has a membrane lined with pores, which regulate the movement of RNA and proteins into the nucleus. Lysosomes contain enzymes that carry out hydrolysis to break down old cell parts. Vacuoles store food and carry them to lysosomes for digestion. Important building blocks such as the Rough ER and the Smooth ER make two separate things. The Rough ER makes secreted proteins, membrane components, and glycoproteins. The Smooth ER makes lipids, metabolizes carbs, and stores Ca+2 ions. One example of an internal membrane is the Mitochondrial Membrane, and its purpose is to conduct the process of Oxidative Phosphorylation, which includes the Electron Transport Chain and Chemiosmosis. This process creates between 30 to 32 ATP for the body’s use. This process could be inhibited, leading to a huge energy loss for the organism. If respiration stops working, then the oxygen being taken in by an organism would not reach its way to the blood stream, causing the organism to die.

    42. LO 2.26 The student is able to analyze data to identify phylogenetic patterns or relationships, showing that homeostatic mechanisms reflect both continuity due to common ancestry and change due to evolution in different environments. SP 5.1 The student can analyze data to identify patterns or relationships Although different species of animals are adapted to different environmental temperatures, each species has an optimal temperature range. Thermoregulation helps keep body temperature within that optimal range, enabling cells to function most effectively, even as external temperature fluctuates. Ectotherms gain most of their heat from the surrounding environment, with a metabolic rate so low, that the amount of heat it generates is too small to have much of an effect on body temperature. In contrast, endotherms can use metabolic heat to regulate their body temperatures. Endotherms are capable of performing vigorous activity for much longer than is possible for most ectotherms. Endothermy solves thermal problems of living on land, enabling terrestrial creatures to maintain stable body temperature fluctuations. For example, no ectotherm can be active in the below-freezing weather that prevails during winter over much of Earth’s surface, but many endotherms function very well in these conditions. Most of the time, endothermic vertebrates are warmer than their surroundings, but these animals also have mechanisms for cooling the body in a hot environment, which enables them to withstand heat loads that are intolerable for many ectotherms. All animals are capable of maintaining a stable internal environment; however, the differences in means of reaching homeostasis emerge when considering the environmental variability that exists amongst all organisms. All animals, regardless of phylogeny, habitat, or type of water produced, must attain a balance in water uptake and loss. Osmoconformer’s internal osmolarity is the same as that of its environment, therefore they often live in water that has a very stable composition. Organisms that are osmoregulators must control its internal osmolarity because its body fluids are not isoosmotic with its environment. Animals first evolved in the sea, and more animal phyla are found there than in any other environment, explaining why most marine animals are osmoconformers. Freshwater animals gain water by osmosis and lose salts by diffusion as the osmolarity of their internal fluids is much higher than that of their surroundings. Animals that live in temporary waters have the adaptation of anhydrobiosis which allows them to lose almost all of their body water and survive in a dormant state when their habitats dry up. Land animals have the adaptation of body covers in order to prevent dehydration. In most animals, one or more different types of transport epithelium acts as an essential component of osmotic regulation and metabolic waste disposal. These homeotic mechanisms to attain an osmotic balance suggest a connection to a common ancestor as organisms evolved from the water; however, similarly to thermoregulation, differences emerge when considering the organism’s habitat as marine or terrestrial. M.C. Question Which of the following statements concerning thermoregulation in ectotherms is true? A) They can use metabolic heat to regulate their body temperature B) Most organisms classified as ectotherms are mammals, birds, and insects along with a few fish and reptile species C) They have the advantage of performing vigorous activity for long periods of time due to their ability to generate a large amount of heat metabolically D)They are less equipped to survive extreme frigid weather as most of their heat is gained from the environment FRQ Style Question A)Based on the data presented on the graph on the left, describe thermoregulation as it occurs in an endothermic mammal and ectothermic reptile. B) Compare how environmental adaptations allow fish to survive in a saltwater and freshwater environment.

    43. Answer Key-LO 2.26 MC Question Which of the following statements concerning thermoregulation in ectotherms is true? A) They can use metabolic heat to regulate their body temperature B) Most organisms classified as ectotherms are mammals, birds, and insects along with a few fish and reptile species C) They have the advantage of performing vigorous activity for long periods of time due to their ability to generate a large amount of heat metabolically D)They are less equipped to survive extreme frigid weather as most of their heat is gained from the environment FRQ Question A)Based on the data presented on the graph to the left, describe thermoregulation as it occurs in an endothermic mammal and ectothermic reptile. Explain the advantages of each. B) Compare how anatomical adaptations allow fish to regulate osmolarity in a saltwater and freshwater environment. A) Using its high metabolic rate to generate heat, the bobcat maintains a stable body temperature across a wide range of environmental temperatures. The snake, meanwhile, generates relatively little metabolic heat and conforms to the temperature of its immediate environment. The bobcat, being an endotherm, has the advantage of performing vigorous activity for much longer than an ectotherm, allowing it to sustain long-distance running. As a terrestrial animal, the bobcat will be able to maintain its stable body temperature in the face of environmental fluctuations. Ectotherms have the advantage of tolerating fluctuations in internal temperature. Ectotherms can consume less food (based on body size) compared to endotherms. This adaptation becomes extremely advantageous when supplies are limited. B) Marine bony fishes, such as cod, are hypoosmotic to seawater and constantly lose water by osmosis and gain salt both by diffusion and from the food they eat. The fishes balance the water loss by drinking large amounts of seawater. Their gills and skin dispose of sodium chloride; in the gills, specialized chloride cells actively transport chloride ions out, and sodium ions follow passively. The kidneys of marine fishes dispose of excess calcium, magnesium, and sulfate ions while excreting only small amounts of water. The osmoregulatory problems of freshwater animals are opposite those of marine animals. The body fluids of most freshwater animals have lower solute concentrations compared to their marine relatives, an adaptation to their low-salinity freshwater habitat. Water balance is maintained by excreting large amounts of very dilute urine. Salts lost by diffusion and in the urine are replenished by foods and by uptake across the gills;chloride cells in the gills actively transport chloride and sodium follows.

    44. LO 1.23: The student is able to justify the selection of data that address questions related to reproductive isolation and speciation. SP 4.1: The student can justify the selection of the kind of data needed to answer a particular scientific question. Explanation: Speciation can occur as a result of reproductive isolation. There are two types of mechanisms that cause reproductive isolation, prezygotic and postzygotic mechanisms. It is a common misconception that reproductive isolation always refers to physical barriers. Data can be used to defend or challenge concepts such as this. An example of the importance of the justification of date is with reproductive isolation and speciation in primates, which underwent these processes over millions of years. When studying these animals, it is important to select data that considers the amount of time, rather than data that is limited to a short amount of time. MC Question: Which of the following would provide data favorable for the study of reproductive isolation and speciation of closely related species? A) Multiple species under the same order that live in different biomes B) A population of a species that was recently separated by the construction of a highway C) Multiple species under the same genus that live in an isolated group of islands D) A population of a species that has been observed to have lower birth rates for a number of years FRQ Question: Explain why the data provided by the beaks of Darwin’s finches is significant and helpful to the study of the reproductive isolation and speciation of these birds (see following figure). Identify the possible reproductive barrier mechanism that caused the isolation. Discuss how genetic testing could possibly provide more reliable data.

    45. Answer Key LO 1.23 Which of the following would provide data favorable for the study of reproductive isolation and speciation of closely related species? A) Multiple species under the same order that live in different biomes B) A population of a species that was recently separated by the construction of a highway C) Multiple species under the same genus that live in an isolated group of islands D) A population of a species that has been observed to have lower birth rates for a number of years Explain why the data provided by the beaks of Darwin’s finches is significant and helpful to the study of the reproductive isolation and speciation of these birds (see following figure). Identify a possible reproductive barrier mechanism related to the speciation. Discuss how genetic testing could possibly provide more reliable data. The data provided by the beaks of the finches provides insight to the diets of the birds. This allows us to understand what could have caused reproductive isolation in this case. The varied diets suggest that the birds were geographically isolated into different habitats, causing different diets and mutations to arise. This can be seen in the beaks of the birds. This is a form of prezygotic isolation, and it led to the speciation of the birds. Genetic testing would provide more exact data pertaining to exactly where and when species branched off from one another.

    46. SP 7.2: The student can connect concepts in and across domain(s) to generalize or extrapolate in and/or across enduring understandings and/or big ideas. Explanation: Many biological process involved in growth and reproduction and homeostasis include temporal regulation and coordination. Timing and regulation of physiological evens are regulated by multiple mechanisms. In animals, internal and external signals regulate a variety of physiological responses that synchronize with environmental cycles and cues. An example of a physiological response is the Fight-or-Flight response that is regulated by the adrenal gland. In plants, environmental stimuli and internal molecular signaling are involved with the regulation of physiological events. An example of a physiological response in plants is phototropism. Phototropism is the plants movement in response to light (A plants stem tilted toward the light source). Growth hormones cause the stem to tilt, so now the leaves are closer to the light source and aligned to intercept the most light. Behaviors in both animals and plants are triggered by external stimuli and environmental cures and are vital to reproduction, natural selection and survival. M.C. Question: Suppose there is a phoenix roebelenii (miniature palm) in the lobby of a hotel. This lobby is very well lighted and stays lit all night. An employee alerts the hotel management that they need to remove the plant from the lobby. He wants them to move the tree because It will stimulate the stomata to release an excess carbon-dioxide and oxygen Phototropism will occur, causing the tree to bend towards the light source will interfere with the photosynthetic rate causing the tree to grow to rapidly and die Alter the photoperiod of the plant resulting in a disruption of its natural growth cycle LO 2.37: The student is able to connect concepts that describe mechanisms that regulate the timing and coordination of physiological events. Learning Log/FRQ-style Question: Name two plant physiological responses. Explain each.

    47. Answer Key- LO 2.37 Suppose there is a phoenix roebelenii (miniature palm) in the lobby of a hotel. This lobby is very well lighted and stays lit all night. An employee alerts the hotel management that they need to remove the plant from the lobby. He wants them to move the tree because It will stimulate the stomata to release an excess carbon-dioxide and oxygen Phototropism will occur, causing the tree to bend towards the light source will interfere with the photosynthetic rate causing the tree to grow to rapidly and die Alter the photoperiod of the plant resulting in a disruption of its natural growth cycle Name two plant physiological responses. Explain each. - One plant response to light is de-etiolation or the browning or the “greening” of dark-grown potatoes. Here, sunlight is the signal that is received by a phytochrome and it induces a signal transduction pathway as well as causing the influx of Calcium (Ca2+) ions to initiate a 2nd signal transaction pathway. Both pathways lead to transcription of specific genes and translation of the specific de-etiolation proteins. A plant’s physiological response to the length of day and night is photoperiodism. One important response to its photoperiod in some plants is flowering. In these plants, flowering is controlled by the overall length of day and night. Plants are split into two types, long night plants and short night plants. Each one requires a specific amount of darkness to function properly. Because phytochromes are sensitive to either red or far red light, a flash of either during the critical period could disrupt the system. The only flash of light that matters is whatever color is used last.

    48. LO 3.34 : The student is able to construct explanations of cell communication through cell-to-cell direct contact or through chemical signaling. SP 6.2: The student can construct explanations of phenomena based on evidence produced through scientific practices. Explanation: Cells communicate through the use of chemicals, hormones or neurotransmitters for example, and with this communication are able to produce a response that benefits the organism. With the binding of receptors, such as testosterone and insulin, receptors inside the cell or in the membrane of the cell cause a transduction pathway that activates relay proteins to cause a cellular response. Intracellular receptors reside within a cell and only respond to ligands that are able to pass through the membrane, for example hormones. Intracellular receptors bind to transcription factors and induce transcription and translation to occur producing a response. Ligands that are unable to enter the cell, rely on membrane-bound receptors to cause a response. Most common receptors are G-Protein receptors, tyrosine kinases, and ion gated channels. These receptors phosphorylate proteins to cause a cellular response. During transduction, second messengers may be used to induce a response, such as the use of IP3 to release calcium out of the ER. Calcium can then act as a second messenger and activate relay proteins. In addition, scaffolding proteins may assist in cell communication by activating various proteins at once. Cell communication also occurs through cell to cell direct contact, such as in the case if neurons. Neurons release neurotransmitters into the synapse to be received by the next neuron. During cell differentiation, early embryonic cells communicate as certain cells release chemicals to induce nearby cells to change their gene expression. M.C.Question: All of the following involve cell communication via membrane embedded proteins EXCEPT: A) G-proteins B) Testosterone C) The formation of dimers D) Sodium Ion Channels FRQ-style Question: Describe, in detail, the communication of cells via a hydrophobic ligand and a potential response produced by the ligand. Discuss the source cell, as well as the target cell.

    49. Answer Key All of the following involve cell communication via membrane embedded proteins EXCEPT: A) G-Proteins B) Testosterone C) The formation of dimers D) Sodium Ion Channels Describe, in detail, the communication of cells via a hydrophobic ligand and a potential response produced by the ligand. Discuss the source cell, as well as the target cell. Communication between cells via a hydrophobic ligand could occur between testes cells and skin cells. Testosterone, the hormone released by the testes, reaches the skin cell and acts as a ligand to an intracellular receptor. Testosterone has the ability to enter the cell because of its similar properties with the lipids of the membrane. The ligand binds to the active site of the intracellular receptor, causing the receptor to be activated and enter the nucleus. In the nucleus, the receptor binds to a transcription factor, causing transcription of DNA and translation of the mRNA strand. The synthesis of a protein may cause a response such as hair growth to occur on the skin in response to the ligand testosterone.

    50. LO 2.30: The student can create representations or models to describe nonspecific immune defenses in plants and animals. (See SP 1.1,1.2) SP 1.1: The student can create representations and models of natural or man-made phenomena and systems in the domain. SP 1.2: The student can describe representations and models of natural or man-made phenomena and systems in the domain. Explanation: Plants and animals have multiple, nonspecific immune responses. Nonspecific immune response is the first and second line of defense when a foreign object tries to enter the body. The response will attack anything that it comes in contact with. Parts of the nonspecific immune responses are: defense barriers, inflammatory response, and fevers. The defense barriers in animals include skin, hair, and tears. Plants do not have specific defense systems like animals. Plant possess nonspecific immune responses like macrophage, which are known as cell eaters. When a plant detects a part is affected by infection, it triggers rapid localized programmed cell death, the microphage, to stop further infection. M.C. Question: Leukocytes ingest pathogens and digest these pathogens with the help of lysosomes. When studying lysosomes which type of cell would probably provide the best opportunity? • Leaf cell of a plant • Phagocytic white blood cell • Bacterial cell • Nerve cell Learning Log/FRQ-style Question: Animals come in contact with many pathogens, and rely on their nonspecific Immune defenses to prevent the entry of pathogens in their bodies. A) List THREE common types of invaders that require a systematic defense, and give examples of each. B) Explain how THREE types of nonspecific defenses can prevent the entry of pathogens in animals.