yeah, i can't imagine needing to know anything more than that it's a cofactor. i certainly haven't come across any specific mentioning of vitamin functioning in either examkrackers or kaplan material.
Mcat Q from the book of DPG mental:
which of the following are caused by a difficenty is a water solube vitamin
a) scurvy
b) rabies
e) some vitamin E lacking disease
f) fartalysis