(5) Questions about fatty acid synthesis and catabolism What are two differences
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(5) Questions about fatty acid synthesis and catabolism What are two differences between fatty acid synthesis and fatty acid catabolism? (2 points) (A) What molecule do cells use to transport activated acyl units across mitochondrial membranes? (1 point) (B) Which molecule do cells use to specifically transfer 2-carbon (acetyl) units out of mitochondria? (1 point) (C) Glucagon signaling leads (via cAMP) to activation of Protein Kinase A (PKA), which catalyzes the phosphorylation of Acetyl-CoA Carboxylase Does this phosphorylation activate or inactivate Acetyl-CoA Carboxylase? (1 point) (D) (E) Name two allosteric regulators of Acetyl-CoA Carboxylase (2 points)Explanation / Answer
(5) (A) Major differencees between fatty acid synthesis and fatty acid catabolism (degradation) include:
(B) In order to transport activated acyl units across the mitochondrial membrane, cells utilise molecules called carnitine (?-hydroxy-?-trimethyl aminobutyrate). In the presence of the enzyme carnitine acyltransferase I [also called as carnitine palmitoyltransferase I (CPT-I)] present on the outer mitochondrial membrane, fatty acids get attached to the hydroxyl group of carnitine to form fatty acyl-carnitine.
Thus, fatty acyl-carnitine formed is transported across to the mitochondrial matrix in exchange for carnitine via carnitine–acylcarnitine translocase by facilitated diffusion through the carnitine/acyl-carnitine transporter or carrier.
(C) Since acetyl- CoA cannot be directly transferred across the mitochondrial membrane, cells utilize the citrate shuttle as a transport mechanism to specifically transfer 2-carbon (acetyl) units out of mitochondria using acetytl-CoA molecules. Citrate synthesized from oxaloacetate and acetyl-CoA is transported from mitochondria to the cytosol via the tricarboxylate anion carrier system and cleaved to yield acetyl CoA and oxaloacetate
(D) PKA mediated phosphorylation o fAcetyl- CoA Carboxylase (ACC) results in inactivation of the enzyme.
(E) Two allosteric regulators of Acetyl- CoA Carboxylase enzyme are glutamate and dicarboxylic acids which act as activators and negative regulators are long and short fatty acid acyl CoA.
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