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Respiration II Does NADH have more or less potential p energy than NAD+? Explain why or why not. What is a “proton motive force?” Oxygen has a very low redox potential, so it pulls low‐ energy electrons out of the ETC efficiently. gy y Suppose a mutation allowed some humans to breathe in sulfur dioxide, instead of oxygen. Sulfur dioxide has a hi h higher redox d potential than oxygen. i l h Would these mutants have complex IV? Would they produce more or less ATP than wild‐type humans? SO2 Krebs Cycle: An overview A i A series of carboxylic acids is oxidized f b li id i idi d Citrate Isocitrate -Ketoglutarate Succinyl CoA Succinate Fumarate Malate Oxaloacetate More reduced More oxidized Why is it considered a cycle? 6C ‘Incoming’ Citrate Isocitrate 2C Oxaloacetate 5C 4C Malate Fumarate -Ketoglutarate Succinyl CoA Are the enzymes that catalyze y y each reaction lined up, either side by side or in a circular formation? Succinate What are the 6 C, 5 C, 4 C etc. What are the 6 C 5 C 4 C etc labels all about? Krebs Cycle: Key observations • Starts with Acetyl CoA • ____ reactions, each reactions each turn of the cycle Of these: • ___ yield(s) NADH or FADH2 or FADH • ___ yield(s) ATP or GTP • ___ is/are “d “decarboxylation” b l ti ” Krebs Cycle: Succinate Fumarate is a redox reaction How many C‐H and C‐C bonds in succinate versus fumarate? O‐— C = O FAD O‐— C = O H — C — H C — H H — C — H C — H O‐— C = O O‐— C = O FADH2 How many electrons and protons move from succinate to FAD? How many electrons and protons move from succinate to FAD? Working backwards through cellular respiration: The citric acid cycle 1) completes the oxidation of glucose it i id l 1) l t th id ti f l (releases CO2); and 2) produces NADH and FADH2 that feed the ETC feed the ETC. What does it mean to say that glucose has been completely oxidized? III. How does pyruvate processing produce NADH? CoA NOTE: the 4 NADH/FADH NOTE: the 4 NADH/FADH2 and and the 1 ATP/GTP from the Krebs cycle are produced via oxidation cycle are produced via oxidation of 4 C‐C/C‐H bonds in this acetyl group. Explain why the following statement is accurate: During cellular respiration, most of the energy in During cellular respiration most of the energy in glucose ends up in two acetyl groups. Working backwards through cellular respiration: Pyruvate processing 1) converts pyruvate to acetyl CoA; 2) produces processing 1) converts pyruvate to acetyl CoA; 2) produces NADH that feeds the ETC, 3) releases CO2. Mitochondrial matrix Inner membrane y moves into the mitochondrion via co‐ NOTE: Pyruvate transport, against its electrochemical gradient. Glycolysis: from glucose to pyruvate Glucose Trapping Step Commitment Step Why do people talk about an “energy investment phase” of glycolysis f l l i and an “energy payoff phase”? d “ ff h ”? The glycolytic The glycolytic enzymes are found in nearly all organisms. enzymes are found in nearly all organisms What does this observation imply about the evolution of glycolysis? Working backwards through cellular respiration: Working backwards through cellular respiration: Glycolysis 1) converts glucose to two molecules of pyruvate; 2) yields 2 ATP; and 3) yields 2 NADH. Cytoplasm Mitochondrial matrix Inner membrane Label glycolysis, pyruvate py processing, citric acid cycle. In terms of redox chemistry where chemistry, where is the “action” (the big potential (the big potential energy drops) in glucose oxidation? Glucose Pyruvate Acetyl CoA Oxaloacetate