100cps4.s09 - Biochemistry & Molecular Biology 100C....

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Biochemistry & Molecular Biology 100C. Problem Set #4 due: May 8, 2009. 1. In vigorously exercising skeletal muscle, protein turnover accelerates; accordingly, large amounts of muscle amino acids are dumped into the blood and taken up by the liver. (a) Diagram a coupled muscle–liver process that accounts for the high rates of L-alanine dumping by skeletal muscle. (b) Why is liver particularly well suited to recycle L-alanine as substrate for gluconueogenesis? (c) Would you expect this process to work equally well in both aerobic and anaerobic muscle? Why? (d) During high protein turnover rates in other animal tissues, L-glutamine, not L-alanine, is exported from tissues. Once in the liver, L-glutamine is hydrolyzed by glutaminase into L-glutamate and ammonium ion. Why do these tissues excrete L-glutamine? (e) By contrast, why does skeletal muscle excrete L-alanine? 2. Hans Krebs was instrumental in characterizing both the citric acid cycle and the mammalian urea cycle. In fact, both cycles can be integrated to form what some have termed the "Krebs
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This note was uploaded on 03/16/2010 for the course BIOC 100A taught by Professor Harrynoller during the Winter '10 term at University of California, Santa Cruz.

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