The Living Environment The study of organisms and their interactions with the environment.
Topics • Unit 1: Ecology • Unit 2: The Cell • Unit 3: Genetics • Unit 4: History of Biological Diversity • Unit 5: The Human Body
Unit 2: The Cell • Chemistry in Biology • Cellular Structure and Function • Cellular Energy • Cellular Reproduction
The Building Blocks of Life • All organisms are made up of carbon-based molecules. Specifically molecules called hydrocarbons. (...they contain C and H) • Macromolecules are large molecules that are formed by joining smaller organic molecules together. There are four major categories of biological macromolecules: • Carbohydrates: store energy and provide structural support. • Lipids: store energy and provide barriers • Proteins: transport substances, speed reactions, provide structural support, and make hormones • Nucleic Acids: store and communicate genetic information
Carbohydrates • The diagram to the right is glucose molecule. • Carbohydrates are compounds composed of carbon, hydrogen, and oxygen. CH2O • Carbohydrates can be simple sugars, monosaccharides, or complex sugars, polysaccharides.
Carbohydrates • Glucose is a simple sugar or monosaccharide. Glucose plays a central role as an energy source for organisms. • Sucrose, such as table sugar and lactose, is a disaccharide. They also serve as an energy source for organisms. • Glycogen is a polysaccharide found as long chains of glucose molecules in the liver and skeletal muscle to be used as stored energy. • Cellulose is also a polysaccharide which is used to give structural support in the cell walls of plant cells. • Chitin is another polysaccharide and is the main component in the hard outer shell of shrimp, lobster, and many insects.
Lipids • The diagram to the right is a phospholipid. • Lipids are composed of fatty acids, glycerol, and other components. • Phospholipids act as barriers because of their hydrophilic, “water-loving” heads and their hydrophobic, “water-fearing” tails.
Proteins • Proteins are made of small carbon compounds called amino acids. There are 20 different amino acids. • There are four conformations of proteins. • Cells contain about 10,000 different proteins that transport substances within the cell and between cells, speed up reactions, communicate signals, and control cell growth.
Proteins as Enzymes • Catalysts are substances which increase the speed of a chemical reaction. • Enzymes are biological catalysts, composed of amino acids, that will speed up the rate of reactions such as photosynthesis and digestion. • Reactants of a chemical reaction are called substrates.
Proteins as Enzymes • When a substrate binds to the active site of an enzymatic protein a reaction occurs forming the products. • Specific enzymes are designed to function only with specific substrates for specific reactions. The two fit like a lock and key. • If a drug is introduced that chemically “fits” into the active site of an enzyme, the enzymatic reaction can be blocked. How Enzymes Work
Proteins as Enzymes • The effectiveness of an enzyme on the rate of the reaction can be affected by factors such as pH and temperature. • Enzymes are typically named after the molecule with which they will interact but end in –ase or –in. For example, amylase, lipase, pepsin, and trypsin are all enzymes.
Nucleic Acids • Nucleic acids are made up of smaller repeating subunits called nucleotides. • There are six major nucleotides all of which contain a phosphate, nitrogenous base, and a ribose sugar. • The main function of nucleic acids is to store and transmit genetic information such as DNA and RNA.
Nucleic Acids • Adenosine triphosphate or ATP is a storehouse of chemical energy used by cells.
The Cell • First discovered in 1665 by Robert Hooke who built one of the first light microscopes and viewed dead cork cells. He is credited for calling them cellulae which eventually became the word cell. • Not long after Hooke, Anton van Leeuwenhoek designed a microscope and viewed living organisms in pond water, milk, and other substances.
The Cell Theory • Developed in the mid 1800’s by German and Prussian scientists it states: • 1. All living organisms are composed of one or more cells. • 2. Cells are the basic unit of structure and organization of all living things. “basic unit of life” – cells perform life functions. • 3. Cells arise only from previously existing cells, with cells passing copies of their genetic material on to their daughter cells.
Types of CellsProkaryote Eukaryote Visualizing Cells
The Plasma Membrane • The main function of the plasma membrane is to maintain the cell’s homeostasis. • A cell’s homeostasis is controlled by the plasma membrane due to its selective permeability.
The Plasma Membrane The Fluid Mosaic Model
The Plasma Membrane • Composed of a phospholipid bilayer, the plasma membrane can maintain its structure due to the polar heads and non-polar tails of the lipids. • Cholesterol molecules between the lipids keep them from sticking together and help the membrane maintain its fluidity. • Carbohydrate chains identify the cell and help the cell identify incoming chemical signals.
The Plasma Membrane • Transport Proteins: move needed substances or waste materials through the plasma membrane. • Receptor Proteins: transmit signals to the inside of the cell. • Support Proteins: anchor the plasma membrane to the cytoskeleton and give the cell its shape.
The Plasma MembraneThe Fluid Mosaic Model • The phospholipids can move sideways within the membrane as well as the proteins. This constant motion of molecules sliding past one another creates a fluidity of the membrane. • Because there are different substances in the membrane, a pattern, or mosaic, is created on its surface.
The Cytoplasm • Cytoplasm is the semi-fluid substance that fills the inside of all cells. • It is composed mostly of water. • In prokaryotes, chemical processes occur directly in the cytoplasm. In eukaryotes these processes occur in organelles.
The Cytoskeleton • The cytoskeleton is a supporting network of long, thin protein fibers that form a framework for the cell. • It is composed of microtubules and microfilaments that support the cell and allow movement of substances within the cell.
The Nucleus • The nucleus is the cell’s control center. • It contains most of the cell’s DNA which is used to make proteins for cell growth, function, and reproduction. • The nucleus is surrounded by a double membrane called the nuclear envelope. It has pores to allow substances to move in and out of the nucleus.
The Nucleus continued… • Within the nucleus is the site of ribosome production called the nucleolus. • As ribosomes are produced they move out of the nucleus and either attach to endoplasmic reticulum or are free floating in the cytoplasm.
Ribosomes • Ribosomes are composed of RNA and protein, and are NOT membrane bound organelles. • The function of ribosomes is to synthesize PROTEINS!
Endoplasmic Reticulum • ER is composed of folded membrane and sacs and is a site for protein and lipid synthesis. • Rough ER is covered by ribosomes that produce proteins. • Smooth ER lacks ribosomes and is a site for polysaccharide and phospholipid synthesis.
Golgi Apparatus • Golgi Apparatus, or Golgi Body, is a flattened stack of folded membranes. • Its function is to modify, sort, and package proteins into sacs called vesicles. • These vesicles can then be shipped outside of the cell. • Sometimes referred to as the cell’s post office.
Vacuoles • A membrane bound sac used to temporarily store food, water, enzymes, and sometimes waste. • Plant cells require very large central vacuoles for storing water.
Mitochondria • Mitochondria have an outer membrane and a folded inner membrane that forms many cristae. • Cristae provide a large surface area for breaking down sugar molecules. • Mitochondria are known as the “powerhouse” of the cell.
Mitochondria • Mitochondria are found in all eukaryotes and are responsible for cellular respiration. • Mitochondria release the energy from nutrients obtained by the cell. • They have their own DNA called mDNA. Because of this fact, they are believed to have once been single celled organisms themselves.
Chloroplasts • Chloroplasts are found only in photosynthetic cells such as plant cells. • They have an outer and inner lipid membrane and contain stacks of thylakoids. • In many ways they are similar to mitochondria but DO NOT perform the same function.
Chloroplasts • Chloroplasts are responsible for using sunlight to produce chemical energy through a process called photosynthesis. • Chloroplasts contain a green pigment that traps sunlight called chlorophyll. • They also have their own DNA and are believed to have once been a single celled organism known as cyanobacteria, possible the first life forms on Earth.
Lysosomes • Lysosomes are membrane bound vesicles that digest excess or worn out organelles and food particles. • They will also digest bacteria and viruses that have entered the cell. • Lysosomes function to keep the inside of the cell clean.
Centrioles • Centrioles are groups of microtubules that function during cell division. • They produce the spindle fibers that separate chromosomes during mitosis and meiosis. • Usually found in pairs called centrioles.