Practice%20Problems%20No_4

Practice%20Problems%20No_4 - 4 Free fatty acid mobilization...

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4. Free fatty acid mobilization from triacylglycerols stored in the adipocytes can be an important energy source under certain metabolic states. Please describe briefly the signal transduction pathway leading to the formation of diacylglycerol from triacylglycerol in response to the binding of such hormones as glucagon and epinephrine to their receptors on the plasma membrane of adipocytes. Key: The binding of glucagon and epinephrine to their receptors on the plasma membrane of adipocytes both result in the activation and dissociation of the alpha subunit of the heterotrimeric guanine nucleotide binding protein (or simply called G protein) from the beta-gamma subunits. The activated, GTP-bound alpha subunit further activates adenylate cyclase that catalyzes the formation of cAMP from ATP. The increased intracellular [cAMP] activates protein kinase A (PKA) that phosphorylates and thus activates triacylglycerol lipase (also known as hormone- sensitive lipase) that catalyzes the hydrolysis of triacylglycerol to form diacylglycerol. 5. Please describe the processes of fatty acid activation and the subsequent transport into mitochondrial matrix before the fatty acid oxidation takes place in the mitochondrial matrix. Key: Fatty acid activation refers to the conversion of a fatty acid to a fatty acyl-CoA, a process catalyzed by an acyl-CoA synthetase bound to the outer mitochondrial membrane. Thus, the fatty acyl-CoA generated outside the mitochondrial matrix has to be transported into the matrix because fatty acid beta-oxidation takes place inside the matrix. Catalyzed by carnitine palmitoyltransferase I, a fatty acyl-CoA transfers its fatty acyl chain onto carnitine to form fatty
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This note was uploaded on 04/29/2008 for the course 3150 402 taught by Professor Zheng during the Spring '08 term at The University of Akron.

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Practice%20Problems%20No_4 - 4 Free fatty acid mobilization...

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