AP BIOLOGY Chapter 7 Cellular Respiration =

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1 1 AP BIOLOGY Chapter 7 Cellular Respiration = Day 1 p. I. Overview A. Cellular Respiration 1. Respiration breathing, exchange of O 2 for CO 2 2. Cellular respiration aerobic harvesting of energy from food molecules by cells. a. Energy is in the form of ATP. b. Energy is then used to do work. B. ATP Molecules/Usage 1. The overall equation for cellular respiration is as follows: 2. Glucose releases chemical energy. 3. Cells store energy in the chemical bonds of the ATP molecule. a. Equation: b. Hydrolyze ATP which means? c. Break the high energy bonds between phosphates energy. 4. Energy from ATP is used for body maintenance and voluntary activities. II. Basic Mechanisms of Energy Release and Storage A. Energy Release 1. Glucose is broken down is a series of steps. 2. The energy is carried by electrons, which are being rearranged from one molecule to another. 3. The basic mechanism is based on the principle of redox. B. Redox Reactions 1. Redox stands for: Reduction-Oxidation. 2. The addition of electrons to another substance is reduction. 3. A loss of electrons from one substance is called oxidation.

2 2 - LEO goes GER 4. Examples: C. Redox and Respiration 1. Glucose is eventually oxidized to CO 2 2. O 2 is eventually reduced to H 2 O. 3. Equation: 4. Glucose donates its electrons (in the form of H atoms) to oxygen two at a time. a. An enzyme known as dehydrogenase is used. b. A coenzyme known as NAD + is also used in the reaction it is an electron acceptor. 5. The enzyme transfers H atoms (two at a time) from the molecule of glucose. a. It removes 2 protons (2 H + ) and two electrons (2 e - ) b. The NAD + picks up the electrons and one H+ and becomes NADH (a hydrogen carrier). c. The other H + goes into the surrounding solution in the cell. 6. The NADH molecules deliver the electrons to an electron carrier molecule in the electron transport chain. a. As the electrons pass along the chain, they lose energy each step. b. The cell uses this to make ATP. D. Two Mechanisms Generate ATP : in humans = 1. Oxidative Phosphorylation (Chemiosmosis) involves membranes and a protein complex called ATP synthase. a. ATP synthases synthesize ATP using the energy stored in concentration gradients of H + ions (protons) across membranes. b. Cells generate most of their ATP this way.

3 3 2. Substrate-level phosphorylation is much simpler than chemiosmosis and does not involve membranes. a. An enzyme transfers a phosphate group from an organic substrate molecule to ADP. b. The substrate is produced as glucose is converted to CO 2 c. The reaction products are a new organic molecule and ATP. d. This accounts for only a small amount of ATP that the cell makes. Day 2 p. III. The Stages of Cellular Respiration A. Overview 1. The first two stages, glycolysis and the Kreb s cycle, are exergonic processes that break down glucose and other organic fuels. a. Glycolysis occurs in the cytoplasm of the cell it begins cellular respiration by breaking down glucose into two molecules of pyruvic acid. b. The Kreb s cycle takes place in the mitochondria it completes the breakdown of glucose by decomposing a derivative of pyruvic acid to carbon dioxide. c. The electron transport chain obtains electrons from hydrogen carries making lots of ATP as the electrons fall down an energy hill of electron carriers. 2. Glycolysis and the Kreb s cycle are energy releasing stages that extract electrons from food molecules. B. Glycolysis = 1. A molecule of glucose is energized using ATP. 2. A six-carbon intermediate ( ) splits into two threecarbon intermediates ( ). 3. A redox reaction generates NADH.

4 4 4. ATP and two molecules of pyruvic acid are produced. a. Get two ATP for each intermediate converted to pyruvic acid. b. Make 4 ATP (net 2 ATP) why net 2? c. Overall diagram: C. Formation of Acetyl coa 1. The three-carbon pyruvic acid becomes oxidized, loses CO 2, and becomes a 2-C acetyl group. 2. It combines with coenzyme A, making acetyl coa. 3. The acetyl coa gets fed into the Kreb s cycle. 4. The Kreb s cycle takes place in the mitochondria the products must be moved from the cytoplasm (loss of 2 ATP). D. The Kreb s Cycle 1. Acetyl coa combines with a 4-C called oxaloacetic acid (OAA). a. This forms citric acid. b. How many carbons does this have? c. The coa will pop off & return to the beginning of the process why? 2. A molecule of water is removed and then one is added back on. a. This makes isocitric acid. b. Relationship? 3. This substrate then loses a CO 2 molecule and two H. a. The remaining 5-C compound is known as ketoglutaric acid. 4. This compound loses a CO 2, two H, and another coenzyme is added on. a. This forms succinyl coa.

5 b. This has how many carbons? 5. The coa pops off and ATP is generated by substrate level phosphorylation. a. Succinic acid is formed. b. How many carbons does this have? 6. A new electron carrier comes in and picks up two H making fumaric acid. a. How many carbons does fumaric acid have? b. The electron carrier is called FAD when it is full it is called FADH 2 7. Water is added and malic acid is formed. 8. A hydrogen carrier removes 2 H, regenerating OAA. *Cake is kinda sweet so feed me one! 5

6 6 Day 3 p. E. The Results of the Kreb s Cycle Glycolysis P.A. to ACo to mitochondria Krebs ATP NADH FADH 2 1. When oxaloacetic acid is regenerated, the cycle will begin again why? 2. A total of 8 hydrogens are released. a. The H are picked up by NAD + and FAD. b. Makes NADH (3), FADH 2 (1), and ATP (1) all x 2 (why?). 3. The NADH and FADH 2 donate their electrons to the third stage the electron transport chain. F. The Electron Transport Chain 1. The electron transport chain uses chemical energy to create an H + gradient and then uses energy stored in the gradient to drive ATP synthesis. Where? 2. A total of 10 NADH and 2 FADH 2 donate their electrons to the carriers on the chain. a. Each carrier ( ) is a different molecule (mostly proteins). b. The carriers reside in 3 protein complexes, which span the inner membrane in the mitochondria. c. The first one is oxidized as the next one is reduced, and so on, down to the last molecule O 2 d. The electron carriers get increasingly more electronegative, as you move from left to right. e. All the carriers bind and release electrons in redox reactions. 3. As redox occurs, the protein complexes use energy released from the electrons to actively transport H + ions from one side of the membrane to the other. a. The H + ions are stored up (potential energy) to make ATP. 4. The H + ions have a tendency to move back across the membrane to the matrix (due to energy of the gradient). a. They move through a special protein port. b. ATP synthase provides the channel opening and contains enzymes to make ATP.

7 c. ADP is then phosphorylated to make ATP. 5. Each oxygen atom in O 2 combines with 2 electrons and with 2 H + ions (from the surrounding solution) to form H 2 O. 6. Overall ATP made: a. 2.5 ATP for each NADH 2.5 x 10 = 25 ATP. b. 1.5 ATP for each FADH x 2 = 3 ATP. c. A grand total of 28 ATP are made from the ETC. 7

8 8 7. Various poisons interfere with ETC examples are cyanide and carbon monoxide. a. They block the movement of electrons. b. They block the flow of H + through ATP synthase. c. They allow H + to leak through the membrane. IV. Fermentation No O 2 A. Anaerobic Respiration 1. Alcohol fermentation in yeasts, certain bacteria. a. Equation: b. NAD + must be regenerated how? c. Example: 2. Lactic Acid Fermentation a. Equation: b. Lactic acid can accumulate as a waste product. c. Example: 3. Obligate anaerobes are poisoned by oxygen live deep in the soil. 4. Facultative anaerobes (such as yeast) can survive with or without. a. If O 2 is present they go through cellular respiration. b. If no O 2 they will ferment. V. Food for Fuel A. Organic Molecules 1. Molecules other than glucose can be used as fuel.

9 9 2. Polysaccharides can be hydrolyzed to monosaccharides and then converted to glucose for glycolysis. 3. Proteins can be digested for amino acids. a. The amino groups are disposed of in the urine. b. The remains are oxidized in the Kreb s cycle. 4. Fats, rich in hydrogen, electrons, and energy, are broken up and fed into glycolysis and the Kreb s cycle. p. 152 If we eat more food than we need, we store fat even if our diet is fatfree. B. Raw Materials 1. In addition to energy, cells need raw materials for growth and repair. a. Some of these things are obtained from food. b. Others are made as intermediates from glycolysis and the Kreb s cycle. 2. This process, known as biosynthesis, consumes ATP. a. All organisms have the ability to harvest energy from organic molecules. b. But plants can also make these molecules from inorganic sources by photosynthesis.