The grades matter but not as much as research and letters of rec. You need to commit a lot of your time to research and convince some people that you are a great candidate for graduate school. Chemistry graduate school is about the research and I think that schools looking at your application need to know that you have the ability and desire to do graduate level research. The way that they are going to know that is through your letters of rec and your statement of purpose.
This is just coming from someone who is finishing up the application season. I would just drill it into you...research, research, research...get to it. In synthetic research it would be difficult to make much of an impact in 1 semester and I would imagine the same has to be true for pchem research. It is good that you are getting into research this summer for sure.
