If you're like me and plan ahead for everything, including the MCAT and med school applications, I'd do this:
First, figure out what you're interested in.
At the end of your first year as a life sciences student, you have to apply to a second year program which is what you will major in. You can easily find these programs in the undergraduate calendar.
Take a look at the programs and figure out what you might be interested and then look at the first-year prerequisites that you need to get in.
Make sure you have all these prerequisites. (they are usually the same for most of the programs, give or take one course here and there)
You have to remember that the MCAT is still a long time away and you should be preparing more for what you are going to do with your undergraduate degree.
the required courses for Life Sciences 1 prepare you a lot for the MCAT.
In second year, take organic chemistry, as this is a main section on the MCAT.. many second year science courses require you to take orgo anyways.
you should be fine doing this, but try not to worry too much about the MCAT right now anyways.
worry about surviving your first year