i agree w/ befreedman - i decided that i would be dedicating my whole life to biology and medicine, so undergrad was my chance to do something different. so i majored in english, read a lot of books, minored in foreign language and took a lot of fun classes. in the end, i got a biology major too b/c it only took a few extra classes after the pre-med ones. but during interviews, everyone wanted to talk about books and foreign travel - NOBODY asked me about my micro class.
if you do something that interests you (doctors are supposed to be people patients can relate with - so having interests other than micro-bio or chem are actually a strength), you will stand out. if you think like you are just a pre-med, you will look like every other pre-med. as long as you do well in your science classes, do whatever you want b/c you will never get the chance to study so many different things at once... take advantage of it - you'll learn plenty of bio in med school, and it'll give you something interesting to talk about!