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8 Cards in this Set
- Front
- Back
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Transport form of Acetyl CoA into the cytosol:
First rate-limiting step of fatty acid synthesis: How is A CoA carboxylase activated? Role of AmpK? |
citrate
acetyl CoA carboxylase - converts A CoA to malonyl CoA dephosphorylated by protein phosphatase 2A (promoted by insulin) AmpK phosphorylates A CoA carboxylase, inactivating |
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Cofactors for A CoA carboxylase:
Regulation of Acetyl CoA carboxylase by citrate: Palmitoyl CoA also inhibits what else? |
ATP, CO2, Mg++, biotin
citrate allosterically stimulates phosphorylated A CoA carboxylase (high ATP, acetyl CoA levels makes high citrate) counteracted by palmitoyl CoA (excess of FA's) translocase - prevents transport of citrate into cytosol G-6-PD - stops NADPH generation |
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Explain role of ACP's in FA synthesis:
How many acetyl CoA's are required to make palmitate? Structure of FA synthase? |
FA synthase mediates formation of acetyl and malonyl ACP's (acyl-carrier-proteins);
Transacylases convert A/M CoA + ACP to A/M ACP + CoA 8 A CoA's dimer of identical polypeptides head-to-tail; 7 distinct enzyme activities + ACP |
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Compare/contrast synthesis vs B-oxidation of FA's:
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synthesis:
citrate, cytoplasm, ACP, FA synthase, acetyl CoA, reduced by NADPH B-oxidation: carnitine transport, mitochondrial matrix, coenzyme A, oxidized by NAD+ and FAD |
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Main site of long-term energy storage:
TAG formation involves what intermediates in the liver, adipose tissue? Explain conversion of G-3-P to TAG: |
adipose tissue
G-3-P, phosphatidic acid acyl transferase adds acyl group phosphatidate phosphatase removes -P diglyceride acyltransferase adds acyl group |
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Insulin's effect on acetyl CoA carboxylase:
How are TAG's changed before entering adipocytes? Rate of TAG formation is controlled by: |
stimulates glycolysis --> increased pyruvate --> increased Acetyl CoA --> CAC --> increased citrate --> stimulates A CoA carboxylase
lipoprotein lipase hydrolyzes G-3-P availability (high glucose) |
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Explain pathway of hormone-sensitive lipase:
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Glucagon/epi stimulate adenylyl cylase, forms cAMP --> activates PKA --> phosphorylates HSL + perilipin A; HSl translocates to surface of lipid droplet; perilipin A allows HSL to enter
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Explain role of leptin, and its effect in stable weight, decreased and increased body fat:
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hormone secreted by adipose tissue in response to fat mass; highly expressed in hypothalamus, regulates BW by inhibiting food intake, stimulating energy use
stable weight - 15-20% body fat - food intake = energy use decreased fat - decreased leptin, stimulates food intake increased fat - increased leptin, reduced foot intake; obesity causes desensitization to leptin, increased set point |
