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Unformatted text preview: orm an aqueous channel.
b) What would guide your choice of the lengths of the alpha helices and beta strands?
Both must be long enough to span the membrane (alpha helices at least 20 amino acids long).
c) Would you change the number of alpha helices and beta strands and why?
Increase the number of alpha and beta to make the center larger so that there is a hole for the channel.
9. (4 points)
Briefly explain one of the following (or explain both for extra credit).
a) Why is it worthwhile for the cell to have enzymes to synthesize and degrade glycogen rather than simply
storing glucose itself?
b) Why is it worthwhile for the cell to have additional branching and debranching enzymes rather than storing
glucose as a linear polymer?
Glucose can’t be stored as individual molecules because it would create too much osmotic pressure and the cell
A branched polymer can be synthesized and degraded more rapidly because these processes occur simultaneously
at multiple ends of branches rather than at the single end of a linear polymer. 2 Exam 2 Chem 423 Spring 2011 Name KEY 10. (16 points)
The metabolism of 1 mol of 1,3-bisphosphoglycerate through glycolysis, pyruvate dehydrogenase and the citric
acid cycle yields _3__ mol of CO2, _4__ mol of NADH, _1__ mol of FADH2, and __3_ mol of ATP (or GTP).
11. (16 points) Suppose a mutation occurs at the phosphorylation site of glycogen synthase such that it can no
longer be phosphorylated. Predict the effect on the following in an organism containing this mutant enzyme:
glucose levels low/normal/high? Glycogen synthesis
Either answer accepted: degradation is not directly affected by the mutation, but some students noted tht
the low glucose levels are likely to lead to increased glycogen degradation.
Briefly describe the effect of this mutation on reciprocal regulation of glycogen metabolism by insulin,
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This note was uploaded on 08/24/2013 for the course CHEM 423 taught by Professor Thompson during the Spring '11 term at UMass (Amherst).
- Spring '11