I took a summer Biochem course prior to my MCAT, and when I got to the trial section, I got Biochem. Some of the things were familiar enough (maybe because I knew I was taking the old MCAT and wasn't as...super rigorous about my class over the summer because I was already MCAT studying or ..a bunch of other factors), but dang that was killer. I gave up halfway and just selected random answers 🙂.
I do think you could possibly teach yourself some of the material at a lighter level (I do think you can teach some metabolic pathways and enzyme kinematics, etc yourself), but a couple of other pathways, I think would take some time. That being said, I don't know what parts of Biochem is to be covered on the MCAT. The stuff I got seemed to be more beginning biochem, which probably explains why I was vaguely familiar..