Question

How does fatty acid biosynthesis end?

(a) By cleaving palmitic acid (C16:0) using a thioesterase
(b) By cleaving stearic acid (C18:0) using a thiolase
(c) By cleaving palmitoyl-CoA (C16:0-CoA) using ATP
(d) By undergoing further reactions

Answer 1

Fatty acid biosynthesis ends with the cleavage of palmitic acid (C16:0) from the ACP by a thioesterase enzyme, producing free palmitic acid which then forms palmitoyl-CoA.

Step-by-step explanation:

Fatty acid biosynthesis ends with the cleaving of palmitic acid (C16:0) from the fatty acid synthase complex. This process is facilitated by a thioesterase enzyme which hydrolyzes the thioester bond between the fatty acid chain and the acyl carrier protein (ACP). The cycle proceeds through 7 turns to yield palmitoyl-ACP, which, after cleaving, immediately reacts with coenzyme-A to form palmitoyl-CoA in the cell. This synthesis stops after sixteen carbons have been added, which is the typical length for palmitate, and any further elongation or desaturation occurs by separate enzyme systems, not the fatty acid synthase complex.