I'm taking the MCAT this April, but from what I've found on the practice tests, Human Physiology is GREATLY beneficial, Biochem helps, and Cell Physiology helps (it's just about the same as Biochem). But to reiterate what scooter said, none are required, and all the necessary info (plus some!) can be found in the Science Review from TPR (I'm sure in the Kaplan one too, but I haven't looked at that material). Good luck!