MBMB 451b

Copyright 2000, E.C. Niederhoffer

Bonus Problem - Metabolism

A rat was fed 14C-labeled acetate. Some of the label appears in glycogen extracted from its muscles. Explain.

For full credit, you must show your work (how you obtained your answer).

Animals cannot carry out the net synthesis of glucose from acetyl-CoA (to which acetate is converted by the enzyme acetate thiokinase).

14C-labeled acetyl-CoA nevertheless enters the citric acid cycle and thereby contributes 14C to oxaloacetate (2 other C atoms are lost as CO2 in the process so that there is no net synthesis of oxaloacetate). The labeled oxaloacetate may be converted to glucose through gluconeogenesis and subsequently taken up by muscle and converted to glycogen.


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