hey guys, I'll be attending mac this fall for life science. quick question, is it a requirement to pick a certain specialization second year such as biochem or biophys? or can i take whatever courses im interested in?

You need to have a program that you're registered in...you can choose to remain in life sciences, though.
Every program has requirements, some more so than others. However, there's no degree, at mac or elsewhere, that just allows you to "take whatever courses you're interested in".

you can choose to specialize into one of those programs or you can choose "Honours Life Sciences" which allows you to take a variety of courses related to science that you are actually interested in.