I disagree...I didn't take biochem before the MCAT, but did take OChem II. Thank God I did, because there were passages straight out from carbonyl chapters in the text book, it seemed. BioChem is nice for learning enzymes mechanics, but you should pick those up in your basic bio courses. The prof I had for BC focused mainly on specific enzymes and their actions and structure, which didn't help much on the test. Remember, the MCAT is looking more for thought processes, not specific facts...you learn the concepts of BC in any decent Ochem course.
Dr. Sig