Almost all of your classes will be graded on a curve. There are a few scattered pass/no pass classes (such as research orientation classes), but those are 1.0 credit classes. Immunology used to be pass/no pass, but because of some students complaining about the lack of a grade (sorry, it was from my class but not including me!), it is now graded. You also get graded in clinic, and most people get around a B+ to A.
The curve works fairly well. The averages are usually high (our class average was a 98% on our first optics midterm), so youll be ok if you score around the mean or if you arent among the bottom ~5 scores of your class.