Question

1-Explain how the synthesis of fatty acids is regulated (35 points).

2-Explain how beta-oxidation and fatty acids synthesis are reciprocally regulated (30 points). .

2- Explain how insulin and glucagon regulate lipolysis (35 points).

Answer 1

1) Fatty acid synthesis is regulated by the enzymes acetyl coA carboxylase and fatty acid synthetase. The conversion of acetyl coA to malonyl coA by the enzyme acetyl coA carboxylase is the rate limiting step in the synthesis of fatty acids. The enzyme acetyl coA carboxylase can be controlled in the following ways,

1. Short term control: allosteric control by local metabolites. Palmitoyl coA Caracas a feedback inhibitor and citrate acts as an activator. Phosphorylation and dephosphorylation (covalent modification) of the enzyme by the action of hormones insulin, glucagon and glucglucocorticoids.
2. Long term control: induction and depression if gene that codes for acetyl coA carboxylase.

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