ZieglerLecture13-PDH-TCAcycle

ZieglerLecture13-PDH-TCAcycle - Lecture 13: Lecture 13: The...

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Unformatted text preview: Lecture 13: Lecture 13: The PDH Reaction and The PDH Reaction and the TCA Cycle the TCA Cycle BIOCHEMISTRY 100 Winter 2011 M. Ziegler Learning Objectives Learning Objectives 1. Terminology : amphibolic, anaplerotic 2. Write the overall pyruvate dehydrogenase (PDH) reaction and all 8 reactions of the TCA cycle (citric acid cycle) in order (or any one of them), with structures of substrates and products, names (but not detailed structures) of coenzymes involved, and names of enzymes, and describe what each reaction is accomplishing. 3. State how many enzymes and how many coenzymes are involved in the PDH reaction, name those coenzymes, and (briefly) describe the role each coenzyme plays in the reaction (with the order in which they act). 4. Describe the -ketoglutarate dehydrogenase reaction ( -KGDH) in terms of its similarity to the PDH reaction. 5. State in which steps (PDH and TCA cycle) CO 2 is produced (those steps are always irreversible), which steps involve substrate-level phosphorylation, which steps generate NADH, and which steps generate FADH 2 . 6. How many electrons are carried by NADH? by FADH 2 ? In aerobic metabolism, where do those electrons go (how are the coenzymes regenerated in oxidized form?) 7. Write a balanced reaction starting with 1 pyruvate for PDH, for the TCA cycle, and for the sum of the two. How would the stoichiometries change if you started with the number of pyruvates from 1 glucose? Learning Objectives, continued Learning Objectives, continued 1. Name the 4 main regulated enzymes in aerobic metabolism of pyruvate (PDH and TCA cycle), rationalize why each is regulated, and name the main activators and inhibitors for each reaction. Explain how the regulation of each step related to the ADP or AMP/ATP ratio and/or the NADH/NAD + ratio. 2. How are TCA cycle intermediates replenished when their concentrations have been depleted by using them as precursors in anabolic processes? 3. Write the reaction for the 4th fate of pyruvate to form oxaloacetate (OAA), including enzyme name, reactants and products and any coenzyme(s) needed. Where did you see this reaction before? 4. What controls whether mitochondrial pyruvate is converted to acetyl-CoA or to OAA? 5. Explain two ways in which cells can obtain NADPH in the cytosol for reductive biosyntheses (anabolic processes). (One of these was covered in the gluconeogenesis/glycogen lecture. You dont need to write the details of the other mechanism, involving 2 reactions, just the net effect of those 2 reactions -- where the electrons came from for making NADPH.) 6. What compounds are used to shuttle a) oxaloacetate and b) acetyl-CoA out of the mitochondrion into the cytosol for use in cytosolic biosynthetic processes, like gluconeogenesis and fatty acid biosynthesis? Where weve been and where were going Where weve been and where were going glycogen UDP-glucose G-1-P G-6-P glycolysis (10 steps) gluconeogenesis (11 steps) (oxidative) ribulose-5-P ribose-5-P...
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This note was uploaded on 02/04/2011 for the course BCH 100 taught by Professor Staff during the Winter '08 term at UC Riverside.

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ZieglerLecture13-PDH-TCAcycle - Lecture 13: Lecture 13: The...

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