Summary Equation Of Cellular Respiration

AP Biology, Chapter 9
Cellular Respiration and Fermentation

Life is Work

9.1 Catabolic pathways yield energy by oxidizing organic fuels Intro Catabolic Pathways and Production of ATP 1. Distinguish fermentation and cellular respiration. Fermentation Partial degradation of glucose Uses no O2 Yields some ATP Cellular respiration Complete degradation to CO2 and H2O Requires O2 = aerobic Yields much more ATP 2. Describe the summary equation for cellular respiration. Also note the specific chemical equation for the degradation of glucose. Organic compounds + O2 è CO2 + H2O + energy C6H12O6 + 6O2 è 6CO2 + 6H2O + energy (ΔG = -686 kcal/mol) Redox reactions: Oxidation and Reduction
Intro The Principle of Redox 4. Define oxidation and reduction. Oxidation = loss of electrons; really the increase in oxidation number Reduction = gain of electrons; really the decrease in oxidation number 5. Explain how redox reactions are involved in energy exchanges. When electrons are transferred, energy is released or stored Ex. electrons transferred to oxygen fall to lower energy states Oxidation of Organic Fuel Molecules During Cellular Respiration 6. Explain why organic molecules that have an abundance of hydrogen are excellent cellular fuels. Electrons are shared very equally between H and C Equal sharing means high energy Transfer to oxygen releases the energy Stepwise Energy Harvest via NAD+ and the Electron Transport Chain 7. Describe the role of NAD+ and the electron transport chain during respiration. NAD+ + 2H (with their high-energy electrons) è NADH + H+ NADH passes high energy electrons to the top of the electron transport chain As electrons flow, H+ is pumped across the inner mitochondrial membrane O2 accepts the low-energy electrons at the end of the chain 8. Describe the function of a dehydrogenase. Removes high energy electrons and accompanying hydrogen Adds them to a cofactor è NAD The Stages of Cellular Respiration: A Preview 9. Describe the localizations and most important results for the stages of cellular respiration. Glycolysis Cytoplasm Glucose è 2 pyruvate + 2ATP + 2 NADH Pyruvate oxidation Mitochondrial matrix in eukaryotes, cytoplasm in prokaryotes Pyruvate è AcetylCoA + CO2 + NADH Citric acid cycle cycle Mitochondrial matrix in eukaryotes, cytoplasm in prokaryotes Pyruvate è 3CO2 + 3NADH + FADH2 + ATP Electron transport system (ETS) + chemiosmosis = oxidative phosphorylation Mitochondrial inner membrane, bacterial plasma membrane NADH + FADH2 used to make many ATP 10. Contrast oxidative and substrate-level phosphorylation. Both make ATP Oxidative Uses the energy of a H+ gradient ETS pumps H+, oxygen accepts low energy electrons Substrate-level: high E phosphate transferred directly to ADP

9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate Intro 11. Describe how the carbon skeleton of glucose changes as it proceeds through glycolysis. Six-carbon è 2 three-carbon Glucose è pyruvic acid + energy Energy Investment Phase 12. Explain why ATP is required for the preparatory steps of glycolysis. Adds energy to glucose molecule Glucose + 2ATP è fructose 1,6-bisphosphate + 2ADP + 2Pi Breaks more easily F1,6P è 2 glyceraldehyde 3-phosphate Energy Payoff Phase 13.
Identify where sugar oxidation, substrate-level phosphorylation, and the reduction of NAD+ occur in glycolysis. Sugar oxidation/NAD+ reduction Performed by triose phosphate dehydrogenase 2 glyceraldehyde phosphate è 2 1,3-bisphosphoglycerate + 2 NADH Substrate-level phosphorylation 2 1,3-bisphosphoglycerate + 2 ADP è2 3-phosphoglycerate + 2 ATP 2 3-phosphoglycerate è 2 phosphoenolpyruvate Substrate-level phosphorylation (again) Performed by pyruvate kinase 2 phosphoenolpyruvate + 2 ADP è 2 pyruvate + 2 ATP 14. Summarize the energy yield of glycolysis. Lose: 2 ATP getting the process started Gain: 4 ATP and 2 NADH Net: 2 ATP + 2 NADH

9.3 After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules Intro Oxidation of Pyruvate to Acetyl CoA 15. Describe where pyruvate is oxidized to acetyl CoA, what molecules are produced, and how this process links glycolysis to the citric acid cycle. Pyruvate is actively transported into the mitochondrial matrix Performed by pyruvate dehydrogenase complex Pyruvate + Coenzyme A + NAD+ è Acetyl CoA + CO2 +
NADH The acetyl is the remaining high-energy piece of the glucose Acetyl CoA delivers this piece into the citric acid cycle The Citric Acid Cycle 16.
Summarize important phases in the citric acid cycle. Acetyl CoA + oxaloacetate è citrate + CoA Citrate è succinyl CoA + 2CO2 + 2NADH Succinyl CoA è oxaloacetate + ATP + FADH2 + NADH

9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis Intro The Pathway of Electron Transport 17. Where is the energy from the glucose molecule when the citric acid cycle is completed? 4 ATP from substrate-level phosphorylation Much more is present as NADH and FADH2 18. Describe how the exergonic "slide" of electrons down the electron transport chain is coupled to the endergonic production of ATP by chemiosmosis. Electrons lose energy in electron transport = exergonic NADH donates high-energy electrons to a flavoprotein FADH2 feeds in at a lower energy level Also in the chain are Fe·S proteins, ubiquinone, and cytochromes Oxygen accepts low-energy electrons from the last carrier The energy is used to transport H+ out of the matrix Chemiosmosis: The Energy-Coupling
Mechanism 19. Describe the process of chemiosmosis. Electron transport establishes a proton gradient = proton-motive force ATP synthase: ADP + Pi + energy è ATP As ATP is made, H+ diffuses through a channel made by ATP synthase Oxygen ultimately accepts electrons, ATP is made = oxidative phosphorylation 21. Explain how membrane structure is related to membrane function in chemiosmosis. ATP synthase is complex A cylindrical rotor and rod are embedded within the membrane Attached to the rod on the matrix-side of the membrane is catalytic knob The rotor is the channel As H+ flows the rotor spins The rod rotates within the catalytic knob The rods changes the conformation of the catalytic sites ATP is ejected from the catalytic sites as the rod rotates An Accounting of ATP Production by Cellular Respiration 22. Summarize the net ATP yield from the oxidation of a glucose molecule by constructing an ATP ledger that includes coenzyme production during the different stages of glycolysis and cellular respiration. Glycolysis 2 ATP 2 NADH Pyruvate dehydrogenase 2 NADH Citric acid cycle 2 ATP 6 NADH 2 FADH2

d. Oxidative phosphorylation 26-28 ATP e. Total 30-32 ATP

9.5 Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen Intro 23. Distinguish fermentation and anaerobic respiration. Fermentation: ATP made using substrate-level phosphorylation in glycolysis Anaerobic Uses electron transport to make ATP Uses some other ultimate acceptor like sulfate Used by prokaryotes in anaerobic environments 24. Explain why fermentation is necessary. a. Fermentation is anaerobic b. Oxygen is not present to accept drained electrons c. NAD+ needed in glycolysis must be regenerated from NADH Types of fermentation 25. Compare the fate of pyruvate in alcohol fermentation and lactic acid fermentation. Alcohol fermentation 2 pyruvate è 2 CO2 + 2 acetaldehyde 2 acetaldehyde + 2 NADH è 2 ethanol + 2 NAD+ Lactic acid fermentation 2 pyruvate + 2 NADH è 2 lactate + 2 NAD+ Also performed in muscle under anaerobic, strenuous conditions Comparing Fermentation with Anaerobic and Aerobic Respiration 26. Compare the processes of fermentation, aerobic and anaerobic respiration. Similarities All use lycolysis Some ATP made by substrate-level phosphorylation Use NAD+ Key difference: mechanism of NADH è NAD+ Fermentation: by reaction with pyruvate or breakdown products Aerobic: ETS to oxygen Anaerobic: ETS to some other electron acceptor 27. Contrast obligate and facultative anaerobes. Obligate are poisoned by oxygen (Clostridium tetani) Facultative anaerobes include some fungi and bacteria Perform cellular respiration when O2 is present Perform fermentation when its not The Evolutionary Significance of Glycolysis 28. Describe evidence that the first prokaryotes produced ATP by glycolysis. 3.5-2.7 bya: very little oxygen in the atmosphere Highly conserved in evolution Takes place in cytoplasm; no organelle required

9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways Intro The Versatility of Catabolism 29. Describe how food molecules other than glucose can be oxidized to make ATP. Proteins è amino acids è pyruvate + acetyl CoA Fats è glycerol + fatty acids è glyceraldehyde phosphate + acetyl CoA Biosynthesis (Anabolic Pathways) 30. Explain how glycolysis and the Krebs cycle can contribute to anabolic pathways. Intermediates are starting points for making amino acids and fats Amino acids and fats can be interconverted in glycolysis and the Krebs cycle Gluconeogenesis runs glycolysis in reverse when blood sugar is low Regulation of Cellular Respiration via Feedback Mechanisms 31. Explain how ATP production is controlled by the cell and what role the allosteric enzyme phosphofructokinase plays in the process. Feedback inhibition shuts off a pathway when enough product is present Phosphofructokinase Catalyzes last step before commitment to glycolysis Inhibited by ATP and citrate Stimulated by AMP