I just finished my 3rd (of 5) semesters in a traditional BSN program. You will mainly use your A&P. For example, in the MedSurg 1 class that I just finished, when we were doing a unit our teacher would say "You already had A&P so I'm not going to re-teach the A&P for (this system).. You can do that on your own time." Then we would jump right into diseases, syndromes, etc for that body system. To understand what is occurring when "things go wrong", you must have a grasp on when things are working "normally." It really helps to have firm grasp of your Human A&P so you aren't spending time learning it later. (You wont have time to be learning A&P, except for some reviewing here an there!). So far, we honestly haven't had too many topics that have required a lot of chemistry or micro. Like the PP said, it does help to understand microorganisms and how they affect the body, but we haven't gone into too much detail on any of that (so far anyways.) As far as chem, it helps a little when you get to Pharm, but you wont be balancing equations or anything like that. I have a previous degree (BS in Biology with a minor in Chem). I can say I don't recall having used anything I learned in Gen Chem at this point. Biochem helped a bit with Pharm, as far as knowing about RAS system, electrolytes, acid-base imbalances, etc. (I don't think many programs require Biochem though). I wouldn't stress about having to know "everything" about chem and micro In detail for nursing courses. While the main concepts in those classes are important, A&P is the stuff that will be coming up again and again. Best of luck!