PRACTICE SET 6

PRACTICE SET 6 - PRACTICE SET 6 A. Questions on Lipid...

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PRACTICE SET 6 A. Questions on Lipid Metabolism and Glyoxylate Cycle 1. The hydroxy acid given below can be completely oxidized to acetyl-CoA by beta- oxidation. Write the series of individual reactions that will accomplish this degradation. Then write the overall sum showing how much ATP, CoASH and NAD + is required and how much NADH, acetyl-CoA, etc., are produced on a per molar basis. Use structural formulas for all substrates and products and standard abbreviations for cofactors (e.g., NAD + , ATP); balance all equations. 2. Calculate the net number of moles of energy-rich phosphate (ATP equivalents) that should be produced when one mole tricaproin is oxidized in liver mitochonridria completely to CO 2 and H 2 O via beta oxidation and the carbons of glycerol are oxidized to CO 2. Show all calculations. 3. When one mole of arachidonic acid is oxidized to CO 2 and H 2 O by ! -oxidation and the Krebs cycle, how many moles of NADH, FADH 2, ATP, and CO 2 are produced? Arachidonic acid is a C 20 fatty acid with double bonds at carbons 5, 8, 11, 14. C CH 2 H H 3 C OH CC H (CH 2 ) 4 H COO- CH 2 O CHO CH 2 O C C C O O O (CH 2 ) 4 (CH 2 ) 4 (CH 2 ) 4 3 CH 3 CH 3
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4. Compare and contrast the pathway by which fatty acids are degraded (beta- oxidation) with the pathway by which fatty acids are synthesized from acetate. Cover such points as: (a) nature of the "activated" structures; (b) coenzymes involved; (c) stereochemistry of the intermediates; (d) the places in the living cells where the pathways occur; (e) any significant (major) structural differences in any intermediates involved; and (f) the amount of ATP required for the two pathways. Write your answers in table form. 5. Explain in detail why an animal cannot affect the net conversion of lipid to carbohydrate while a plant or microorganism can. Illustrate your answer with the key enzyme-catalyzed reactions involved. 6. Although lipid degradation can not result in the net accumulation of glucose, explain why glycogen and blood glucose become radioactive when 14 C-acetate ( 14 CH 3 COO - ) is fed to experimental animals. 7. The condensation of butyryl-S-ACP with malonyl-S-ACP occurs in fatty acid synthesis when a C 4 -fatty acid is elongated to a C 6 -fatty acid. Please write the structure of the hypothetical seven-carbon-S-ACP b-keto acid intermediate that is formed prior to decarboxylation of the malonyl moiety. The structure of butyryl- S-ACP is given. 8. One reaction of the glyoxylate cycle is formally analogous to the reaction catalyzed by citrate synthase of the Krebs cycle. Write the reaction of the glyxoylate cycle using structures and abbreviations for co-factors. H 3 C CH 2 CH 2 C O S ACP
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B. Questions on Amino Acid Metabolism 9. Give one example of each of the following reactions -- using specific compounds known to undergo those reactions: a. Decarboxylation of an amino acid.
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PRACTICE SET 6 - PRACTICE SET 6 A. Questions on Lipid...

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