4 - MCB102, Summer 2009 - Problem Set 4 Questions for...

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MCB102, Summer 2009 - Problem Set 4 Questions for Tuesday lecture: 1. Mark each statement true or false. If you mark the statement false, please provide a precise and thorough description of what is wrong with it. a. If acetyl CoA, radiolabelled at both carbon positions, is used as fuel by the liver while gluconeogenesis is active, it is possible for the radiolabelled carbons to end up incorporated into the newly synthesized glucose. _______ TRUE _______ FALSE The reason this statement is false is: b. The net result of the citric acid cycle is to produce one additional 4-carbon oxaloacetate molecule for each 2 acetates (from acetyl-CoA) that enter the cycle, resulting in a net increase of the pool of intermediates. _______ TRUE _______ FALSE The reason this statement is false is: 2. Acetyl CoA labeled with 14 C in both its acetyl carbon atoms is incubated with a batch of unlabeled oxaloacetate, and a crude tissue extract with enzymes capable of carrying out the reactions of the citric acid cycle. After one turn of the cycle, you retrieve the resulting oxaloacetate molecules. At which carbon positions will you find 14 C in this batch of oxaloacetate molecules? i. None of the carbon positions. ii. The two carboxyl carbon positions. iii. All four carbon positions iv. The keto carbon and one of the carboxyl carbons. v. No pattern that is predictable from the information provided. Clearly indicate your choice of one of the five answers, and explain briefly: 3. (2008) A batch of radioactively labeled malate, labeled at the carbon starred in the drawing, is provided to actively respiring mitochondria which have a large supply of Acetyl CoA. Considering only the citric acid cycle reactions, in what compound or compounds will the radioactive carbon be found after the cycle is left to run for a long time ( a time long enough for all of the malate to enter and for the carbons to proceed all the way around the cycle several times
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This note was uploaded on 09/28/2009 for the course MCB 102 taught by Professor Staff during the Summer '08 term at Berkeley.

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4 - MCB102, Summer 2009 - Problem Set 4 Questions for...

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