100cps2s09

100cps2s09 - Biochemistry & Molecular Biology 100C...

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Biochemistry & Molecular Biology 100C Problem Set #2 due: April 20, 2009. 1. The enzyme acyl-CoA synthetase, which activates aliphatic, long-chain fatty acids for catabolism, involves ATPαβ hydrolysis (–10.0 kcal/mole under bioenergetic standard conditions). Using additional information provided in lecture and/or text, and given the overall equation for the reaction: RCOO + ATP + CoA-SH ↔ RCO~S-CoA + 5´-AMP + PP i ΔG°´= –2.5 kcal/mole where PP i is the abbreviation for pyrophosphate, P 2 O 7 3– , and CoA-SH that for coenzyme-A, which contains an active sulfhydryl group, (a) Calculate ΔG°´(hydrolysis) for the acyl-thioester product: RCO~S-CoA + H 2 O RCOO + CoA-SH (b) In the “Phospho-Group Transfer Potential” table, an aliphatic acyl-adenylate is listed as ΔG°´= –10.5 kcal/mole. For liver tissue rapidly catabolyzing long-chain fatty acids, ATP is present at 15 m M and RCOO is present at 8 m M steady-state. What minimum steady-state PP i concentration allows formation of the acyl-adenylate intermediate? (c) Conceptually, under what steady-state intracellular conditions are fatty acids "mobilized" for rapid catabolism as cell energy source? (d) Calculate ΔG´ for the formation of the acyl-adenylate intermediate if PP i is actually maintained at 0.1 m M steady-state. (e) Calculate ΔG°´ for the second step in the reaction:
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100cps2s09 - Biochemistry & Molecular Biology 100C...

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