This is essentially what I was getting in with my joke post earlier. If you pay attn in class, you should be able to get hints from the prof as well as your own experience as to what you need to know. Sometimes I would sit in with other students studying and they'd be talking stuff way over my head. They'd be going on and on about some detail of some tangential pathway we mentioned in class as an example of something and while I'd get what they were talking about it would sometimes make me panic for a half a second b/c they knew all these details that I hadn't really paid any attn to. Guess who consistently came out with the 100% and who consistently got a mid-range B? Here's a hint: the people who had memorized everything weren't the ones getting the A. You see, it's all about knowing the concepts. Sure, if the prof had cared about those pathways, I would have learned them, but the fact of the matter was this was an undergraduate introductory course in biochemistry. (Yes, UG 400-level courses are introductory courses. They are generally not advanced courses. You'll get those in grad or med school.) He cared about the fundamental concepts not the small details that frankly nobody has memorized. (I once had a bio professor tell me outright that "[Almost] no one keeps all the individual rxns of the Citric Acid Cycle memorized and ready to recall, because, honestly, either it's not your area of research or, if it is, you're researching one individual rxn for most of your life and that's really all you care about or even know without a reference manual." While I think she was exaggerating a bit there, there is some truth to what she was saying -- namely, you needn't memorize all those little details. Instead, know the big picture and understand it.)