On page 190 in the EK bio 30 minute exam for Lecture one, question number 22 asks what Cofactors are best described as: The answer is C, metal ions or coenzymes that activate an enzyme by binding tightly to it. My question is, why isn't it also A? Aren't they required for enzyme activity, since on page 12 it says that apoenzymes (enzymes without cofactors) are completely non-functional? That kinda confused me.
A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. Apoenzymes are enzymes that require cofactors but don't have it bound to them (you obviously knew this fact). However NOT ALL enzymes without cofactors are apoenzymes.
So now read option A again please with a little more care and diligence
Option A) A non protein chemical compound required for ALL enzyme activity.
Not ALL enzymes require cofactors therefore this answer is incorrect. Whenever you see extreme answers on the MCAT they should bring up red flags.... stuff like ALL, NEVER, ONLY etc....