Question

Fatty Acid Synthesis Assignment

1. Explain how the activation of acetyl-CoA carboxylase prevents excess citrate in the cytosol based on activation of acetyl-CoA carboxylase
2. Explain how the activation of acetyl-CoA carboxylase prevents excess citrate in the cytosol based on activation of acetyl-CoA carboxylase by citrate
3. Describe how fatty acid molecules form from dietary triacylglycerol (TG) in the lumen of the intestine based on enzyme catalyzed reactions on the surface of enterocytes.
4. Describe how fatty acid molecules (but not a polar glycerol molecule) can diffuse into a cell based on the requirements of simple diffusion across a biological membrane

Answer 1

1) Acetyl coA carboxilase consumes the acetyl coA present in cytosol and convert into malanoyl coA irreversibly hence automatically the acetyl coA is regained from other sources like citrate. Hence upon activation of acetyl coA carboxylase citrate levels are reduced.

2)citrate is an allosteric activator of acetyl coA carboxylase, as citrate reverses the inhibition by phosphorylation of acetyl coA carboxylase, hence it will be activated and converts acetylcholine into malonyl coA. As it proceeds ATP lyase enzyme catalyses acetyl coA formation from citrate in prevent exess citrate in cytosol.

3)dietary triacyl glycerides and other fat is stabilises them and made them available for enzymatic reactions on intestinal lumen. Intestinal lumen contains lypase enzyme which degrades triacyl glycerides into monoacyl glycerides and free fatty acids.

4)plasma membrane is selectively permiable to hydrphobic or small polar substances but not to the large polar molecules or ions. Fatty acids are small hydrophobic but triacyl glyceride are large polar substances resisted due to hidrophobic lipid bylayer