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B2 Revision. Topics 1-4. DNA - . Genes are made of a chemical called DNA. In DNA there 4 bases called Adenine, Cytosine, Thymine and Guanine DNA contains instructions for making the cell and telling it what to do.

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B2 Revision

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    1. B2 Revision Topics 1-4

    2. DNA - Genes are made of a chemical called DNA. In DNA there 4 bases called Adenine, Cytosine, Thymine and Guanine DNA contains instructions for making the cell and telling it what to do. DNA gives order of amino acids, only one side acts as a code for making proteins (Coding Strand) Plants and animals have a similar structure. They have a nucleus which holds DNA as a set of chromosomes. Each gene contains information to make one protein.

    3. Fermentation - •A micro-organism is a living thing that is so tiny it can only be seen through a microscope. Scientists cultivate, or grow, microorganisms in a liquid that contains nutrients  - called culture medium. •Scientists have to control the growth carefully otherwise they will produce very quickly. As they grow the microorganisms use up the nutrients in the culture medium and produce waste products and other substances. – this process is called FERMENTATION •We use fermentation for making wine and bear by using yeast. The yeasts uses sugar as a nutrient and as energy. The sugar is broken down to leave two waste products, carbon dioxide and alcohol (ethanol). When making beer or wine, alcohol is the product wanted, however, fermentation by microorganisms can be used to produce many other useful products. To do this, the microorganisms are cultivated in tanks called FERMENTERS. •Microorganisms are grown in fermenters to produce products. Such as yoghurt, cheese, vinegar and soy sauce. They are also used to make a range of different enzymes needed in industrial processes. Moulds and bacteria are used to make antibiotics such as penicillin. These are all examples of fermentation. •Bacteria and other microorganisms contain DNA. They use the same genetic code as humans. Scientists can make the bacteria produce new products by changing their DNA. First they have to identify the protein that is needed as a medicine, such as insulin, which is needed to control diabetes. Then the cut out the section of the human DNA that is used for making insulin. They then add that that DNA to the bacteria. The bacteria now contain the gene for making insulin. If they are cultivated in a fermenter, this will grow massive numbers of bacteria and will produce lots of insulin.

    4. Protein synthesis - To make proteins two things must happen: • The instructions from the code must be carried from the DNA in the nucleus top the ribosomes. TRANSCRIPTION. •  Amino acids must be bought to the ribosomes to be build up into a protein. TRANSLATION. Transcription: It takes place in the nucleus. The DNA unzips and the mRNA enters and copies from the coding strand of the DNA. (But U replaces T). After coping the code the mRNA leaves the nucleus through the 'nucleur pore'. Translation The mRNA goes to the ribosomes in the cytoplasm and the tRNAs bring appropriate amino acids to translate the mRNA. The amino acids join together to form a polypethide and many polypethides make up a protein.

    5. Transcription Protein synthesis -

    6. Translation Protein synthesis -

    7. Respiration - Respiration is the process of breaking down glucose to release energy which takes place in every cell in your body. All living things respire. Aerobic Respiration This is using oxygen- remember 'air'obic. It's the most efficient way to release energy from glucose. Glucose + Oxygen -> Carbon Dioxoide + Water (+ Energy) Anaerobic Respiration This is without oxygen when there is not enough available. It's not the most efficient way. Glucose -> Lactic Acid (+Energy)

    8. Growth -  Cell division results in growth  Growth is a permanent increase in the size or mass of an organism.  All growth results from the production of new calls by Mitosis  the bigger the organism, the more cells it contains. Plants have a special way of growing, when new cells are formed around root and stem tips, their cell walls are still soft.  The cells absorb water into their vacuoles and get longer.  This process is called elongation as the cells get longer the roots or shoots get longer.  The cell wall hardens and the cell keeps its new shape. There are different ways of measuring growth. One way is to simply weigh the organism.  Body cells contain a large amount of water so most of this weight will be water; this is called the wet weight.  The amount of water can vary so the results may be inaccurate. Another, more accurate method is to dry out the body first.  This is called the dry weight.  This method kills the organism, so it if often only used to compare growth in plants. Another way is to look at size and length.  Plants can be measured from the shoot tip to ground level to give their height.  Measuring across the widest part of the plant is called it’s spread.  Height and spread are used by garden centers and plant catalogues so customers know big a plant will grow.

    9. Cell Division -

    10. Stem Cell - Stem cells are found in all multi-cellular organisms. They are characterized by the ability to be able to renew themselves through mitotic cell division and differentiating in a large range of specialized cell types. In a developing embryo, stem cells can differentiate into all of the specialized embryonic tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing specialized cells, but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues. Self-renewal - the ability to go through numerous cycles of cell division while maintaining the undifferentiated state. Potency - the capacity to differentiate into specialized cell types.

    11. Tough Decisions - •Termination – The legal limit for abortion is 23 weeks. This is because after 23 weeks the child is developed enough to be born alive and survive independent of its mothers womb. •There are many people who disagree with the legalization of abortions and believe it’s against human rights. However, as you can see from below, more people support it than not. A 2009 poll by MORI surveyed women's attitudes to abortion. Asking if all women should have the right of access abortion 37% Strongly agree 20% Tend to agree 12% Neither agree nor disagree 7% Tend to disagree 12% Strongly disagree 3% Don't know 9% preferred not to answer

    12. Performance enhancing drugs – •Lean mass builders - used to amplify the growth of muscle and lean body mass, and sometimes to reduce body fat. E.g. anabolic steroids, beta-2 agonists and various human hormones. •Stimulants - used by athletes to stimulate their bodies and perform at optimum level, usually to increase alertness, decrease fatigue, and/or increase aggressiveness. E.g. caffeine and amphetamines. •Painkillers - mask athletes' pain so they can continue to compete and perform beyond their usual pain thresholds. Blood pressure is increased causing the cells in the muscles to be better supplied with oxygen. •Sedatives - used by athletes in sports like archery which require steady hands and precise aim, and also by athletes attempting to overcome nervousness. Alcohol and marijuana are examples. •Diuretics - remove water from athletes' bodies. They are often used by athletes who need to meet weight restrictions. •Masking drugs - used to stop detection of other drugs. An example is the use of epitestosterone, it restores the testosterone to normal levels after anabolic steroid supplementation.

    13. Plant hormones - Auxin - needed for plant growth. It controls the growth of roots and shoots. Auxin is stored in the tips of new shoots and roots, and causes growth by diffusion.     If you cut the tip off a shoot, the shoot will stop growing. If the tip is replaced, it starts to grow again. However, auxin stops sideward growth, so if the tip is removed, the shoot will grow sideways.     There is a different effect of auxin in roots. It prevents growth vertically. This means the root will grow toward moisture, not downward with gravity. This causes a build-up of auxin on the bottom edge of the root.     If there is a build up of auxin on one part of a root or shoot, it causes only the top side to grow, making the shoot/root bend upward/downward respectively.

    14. Plant hormones - Gibberellin - promotes cell division and elongation. It also helps seeds to sprout. Cytokinin - also promotes cell division. High levels of this hormone are found in areas of the plant that require the most growth, such as roots, young leaves and developing fruits and seeds. Abscisic acid - slows down the plant's metabolism so that it doesn't grow during the winter. This leaves the plant more time for phothesis and can help the plant survive harsh winter months. Ethylene - after auxin/gibberellin initiates fruit growth, ethylene helps the fruit to ripen.

    15. Artificial selection - Cut an earthworm in half and its head end will grow a tail. This is called regeneration. Only a few animals have this ability. No mammals have this ability. When an animal loses a part of its body, the cells around the structure change their structure and become less specialized. The cells then differentiate again to produce all the different types of cell needed to grow the new limb. Stem cell research is looking at these animals to try to find a way to regenerate human body parts.

    16. Selective breeding Selective breeding means breeding from individuals that have the characteristics you most want. This increases the chance that more offspring will also have these characteristics. Selective breeding can improve resistance to disease, increase yield and make foods more attractive to consumers. Selective breeding can be used in animals and plants.

    17. Cloning - Cloning is using an organisms DNA to create a genetically identical new organism. 1. A sheep's egg cell is taken and the nucleus is removed. (Haploid-it was a gamete)2. Another nucleus was inserted into the egg cell, it was a diploid nucleus from the cell of a parent sheep. It had the full number of chromosomes. This is nucleus transfer. 3. The cell was stimulated, divided by mitosis and forms an embryo. 4. The embryo was implanted into the uterus of a female sheep, which gives birth to it. The new sheep is genetically identical to the parent  sheep which the nucleus was taken from

    18. Gene therapy - Gene Therapy Could be Used to Treat Genetic Disorders • Gene therapy is a new, experimental treatment for genetic disorders. • It can involve inserting a new, functional version of a faulty gene into a patient’s cells. These cells would then be able to make the correct protein and the symptoms would disappear. • Gene therapy would be targeted at areas that were badly affected by the disease. • In the long term, scientists hope to make these changes to the patient’s DNA permanent, but so far, trails testing gene therapy have only shown very temporary improvements. • Gene therapy still needs a lot of researching and testing. Potential dangers of gene therapy have already been found, e.g. the introduced genetic material could insert into the middle of another gene, causing a whole new set of medical problems, or ‘suicide genes’ could be taken up by health cells.

    19. Cells - Animal cells usually have an irregular shape, and plant cells usually have a regular shape Cells are made up of different parts. It is easier to explain what these parts are by using diagrams like the ones below. Cells are very small. They are the basic building blocks of all animals and plants. Animal cells and plant cells both contain: cell membrane, cytoplasm, nucleus Plant cells also contain these parts, not found in animal cells: chloroplasts, vacuole, cell wall The table summarises the functions of these parts.

    20. Photosynthesis - Photosynthesis is when plants turn energy from the sun into food (Glucose)  by using carbon dioxide. A waste product (Oxygen) is formed.                                   light Carbon  +  Water    -->    Glucose + Oxygen dioxide                                             chlorophyll

    21. Limiting factors to photosynthesis - •Light •Temperature •CO2 levels •Water If any of these increases, the rate of photosynthesis will increase up to a point when one of the others has become the limiting factor. If the temperature exceeds 45 degrees then the enzymes will denature and the rate of photosynthesis will rapidly decrease. 

    22. Carbon cycle -

    23. Nitrogen cycle - Nitrogen is an important element in living things. It is found in proteins and DNA. Plants get nitrogen in the form of nitrates which they get from soil. The nitrogen can then pass into animals as they eat the plants . Nitrogen is naturally recycled in a similar way to the carbon cycle. Nitrogen is mainly recycled by microorganisms in the soil. Decomposers break down dead organisms and animal waste (manure and urea) into ammonia, which contains nitrogen. Nitrifying bacteria then use a series of reactions to convert the ammonia into nitrates that plants can absorb.

    24. Modern agriculture is extremely intensive. The natural nitrogen cycle cannot replace nitrates as quickly as they  are removed, so farmers add industrially made nitrate fertilizers. However this can cause problems in the local rivers.

    25. Deforestation & global warming -

    26. Extreme environments - Organisms need to adapt to survive. They need; a source of energy/food, water, a suitable temperature and a source of oxygen to survive. Black smokers are hydrothermal vents and the environment around them is ‘extreme’. Magma heats up water and it is released as steam through a vent into the sea. This makes the sea hot and acidic. High altitudes (3000m+) are also ‘extreme’. Animals like snow leopards adapt to have thick fur and can cope with low oxygen levels and high levels of UV light. The Antarctic is also ‘extreme’. The temperature can be as low as -70 Degrees Center grade, so animals like penguins have thick fur and fat layers and group together in order to share warmth.

    27. Adaptation - Every organism in a habitat is adapted to living in that habitat. This means they have evolved adaptations to survive in particular conditions or environmental factors. These factors include water, oxygen, light, temperature and the other living organisms in the habitat. If one of these factors change it will effect some of the organisms. Eg: if less light reaches the bottom of a lake, some plants will no longer be able to survive and die out. This causes less food for other organisms living in that habitat. Any organism that can’t adapt to the changes in the environment are likely to have a smaller population. This may cause them to die out altogether and become extinct.

    28. Predation -

    29. Competition -

    30. Air pollution - There are many causes of air pollution, but most of it is made from humans. Nitrous oxide and carbon dioxide are the 2 main pollutants of the air carbon dioxide comes burning our waste and such so we should recycle more. Volcanoes also can be a big cause of air pollution from the gases that are giving off, but when a volcanoes erupts it gives off many dangerous gases that we will end up breathing into our lungs that will damage us but they also damage the environment by emitting some harmful gases. A good example of a harmful gas was the great London smog. This was harming the ozone layer and making it difficult for people to breath outside of their homes. This is affecting many things such as habitats of animals because the gases in the air are causing a lot of acid rain is being produced destroying our environment at the same time as destroying our ozone. The gas that is causing this is sulpher dioxide which we can decrease by taking better care of our environment. We need to act now to make a change for the better soon As you can see by this graph the rise in the pollution in the air has increased dramatically in in the last  2000 years and it is making it more difficult to sort out the problem.

    31. Water pollution - Two main types of water pollution – ACID RAIN and FERTILISERS ACID RAIN The main causes of acid rain are the burning of fuels and vehicle exhausts. These produce the air pollutants of sulphur dioxide (SO2) and Nitrogen oxide (NO2). These pollutants dissolve in water to form acids (ACID RAIN) FERTILISERS 1. The fertiliser runs of into a river or pond. 2. The fertiliser makes the algae grow fast. The increased algae growth cuts out sunlight and uses up oxygen. 3.The plants do not get enough sunlight and they die. Dead plants and algae build up on the river/ pond bed. 4. The dead plants and algae rot, using up oxygen in the water. There are fewer animals in the water.

    32. Recycling - -Recycling has many benefits. If all the glass, metals, plastic and paper in our dustbins were recycled that would be nearly half the contents of the average bin. -  This could reduce the problem of waste disposal and landfill sites that are getting full. -  Recycling uses less energy and produces less damaging carbon dioxide than manufacturing new materials. -  For Example, recycled steel uses 75% less energy and produces only 15% of the carbon dioxide produced when steel is made from iron ore. -  Not everything can be recycled and some materials are more difficult to recycle than others. -  Plastics have to be sorted by hand and many types are not suitable for re-use -  Paper can only be recycled about five times before the fibres become too short and weak. -  Refrigerators are a particular problem because of the harmful gases they contain. -  Although recycling uses less energy and resources it is still an industrial process. -  Some materials need a lot of cleaning and reprocessing. Where materials are difficult to recycle it can be easier and cheaper to make new products.

    33. Environment, the human effect - Human activity can have negative effects on the environment. Manufactured gases called CFCs have damaged the ozone layer in the upper atmosphere. Ozone filters out much of the ultraviolet light from the Sun, which can damage the skin possibly leading to skin cancer. Cases of skin cancer have almost doubled in UK in the last 20 years therefore the ozone layer is not protecting us as well as it used to.

    34. Lichens are good indicators of our impact on the environment as they are very sensitive to air pollution, especially sulphur dioxide. Mayfly larvae are found only in very clean water with lots of oxygen. They are used as living indicators to monitor water quality in streams. Lots of mayfly larvae means that a stream has high quality water.

    35. Species in peril - Species in peril means animals that are rare because they are in danger or cannot adapt to climate change. Every time a species becomes extinct biodiversity is reduced. Careful management of the environment is called conservation. The causes of this are: deforestation, hunting, co2 levels rising, building and economy development, landfill sites. All of these species are forced out of habitats because of these causes and if we cut down on co2 levels and recycle more we could improve the lives of us and animals. More and more plants and animals are become extinct or rare because of the changing climate due to our actions. Two of every five species on the planet that have been assessed by scientist face extinction. THE MAIN CORSE OF EXTINCTION IS PEOPLE!

    36. Conservation managment - Conservation measures protect species by maintaining their habitats and protecting them from poachers and overhunting/havesting There are several reasons why it’s important to conserve species and natural habitats: Protecting endangered species – Many species are becoming endangered, often due to hunting and the destruction of their habitats. They need to be protected to stop them becoming extinct. Protecting the human food supply – Overfishing has greatly reduced fish stocks in the sea. Conservation measures (e.g. quotas on how many fish can be caught) encourage the survival and growth of fish stocks. This protects the food supply for future generations. Maintaining biodiversity – Biodiversity is the variety of different species in a habitat – the more species there are, the greater the biodiversity. If one species in a habitat is destroyed it affects the other species living there – the food web will be affected. It’s important to protect biodiversity. You can… Coppicing – this involves cutting down trees down to just above ground level. The stumps sprout straight, new stems which can be regularly harvested. Reforestation – you can replant to recreate the habitat that has been lost. Replacement planting – This is when new trees are planted at the same rate that others are cutting down. So the total of trees remains the same.

    37. Effects of exercise - When you exercise, your muscles get energy from respiration. Glucose and oxygen must be supplied while carbon dioxide is removed.       glucose + oxygen       carbon dioxide + water (+ energy) If you exercise more vigorously, your muscle cells need more energy to do the extra work. They need to respire faster, this means: More oxygen must be absorbed by your lungs. More carbon dioxide must be removed by your lungs. More oxygen and glucose must be delivered to your muscles by your blood. More carbon dioxide must be removed from your muscles by your blood. Your breathing system and heart have to work harder. You breathe faster and more deeply. This increases the rate of gas exchange in your lungs: more oxygen is absorbed into your blood and more carbon dioxide is removed. Your heart rate also increases, pumping more blood to your muscles.

    38. Improving measurements -