Scoring on the MCAT has almost nothing to do with advanced science knowledge. The standard 8 or so pre-med requirements are WAY more than enough knowledge for the test, at least where I went to undergrad. I majored in sociology, and did the minimum science thing, and did very well--it's not philosophy but it isn't biochem either. So, your major is irrelevant.
Med schools don't care what you know (other than basic stuff, obviously), because you catch up in med school so quickly--a biochem major is even with everyone else almost right off the bat. They care how you think (how smart/scientific you are). And, in my humble opinion, the MCAT does a pretty good job at testing that. Might be a little off topic, sorry.