At my school, most people take one semester of biochem. It covers more, but in less depth. Biochem and molecular biology majors like me, however, take two semesters. We definitely learn things more in depth - it just takes two semesters.
I just finished taking biochem I, and we went over basics of lipids/membranes, sugars, nucleic acids, proteins (heavy emphasis), thermodynamics, types of bonds/H-bonding/water, glycolysis/gluconeogenesis, the Kreb's cycle, the electron transport chain, and photosynthesis. We also had an emphasis on viewing biochem in a quantitative manner, so each of our exams included open response questions where we needed to use calculations. This was by far the easiest way to get points, but was also the most annoying because it required memorizing equations.
Biochem II at my school, which I'm taking semester, has more of a molecular approach and I think talks about things like signal transduction, gene expression, replication, and membrane transport. I'm personally much more stoked for the second half of biochem because I'm slightly more in touch with the second half of my major, lol.
I think one semester is probably more than enough for the MCAT, but there's no harm in taking two semesters!
At my school, the teachers for the general biochem course and for biochem I both kind of suck, but the professors who teach biochem II are known to be pretty good. Going in depth, regardless of the quality of the education, has been helpful to me personally.
