Hi altblue,
I transferred from a CC to Michigan 2 years ago and I'm almost done with my biomedical engineering degree. Community college was a breeze for me (almost 100 credits with 4.0 gpa). I took half my pre-reqs at CC and other other at UM. Classes at Michigan we're not particularly harder because of the material. But, they we're harder to get the A grade because many more students in the class are smart/motivated. You won't be able to study for an exam the night before and do well on it (which was sometimes possible at CC). So, you definitely have to work harder to get the A at the university. Since your premed classes will be in huge lecture halls (something you didn't have to deal with at CC), you should definitely take advantage of professor office hours, university-sponsored study groups, and campus tutoring the minute you feel like you're falling behind. I also suggest that you take only one science class the first semester (if possible) so you don't feel overwhelmed when you come in. My first semester I took an engineering class, a bio class, and a humanities class. It was definitely a big change for me, but it wasn't anything overwhelming. Eventually I took 4 science classes together and was able to get a 4.0 (hardest semester of my life lol). Overall, at UM, it's harder to maintain a 4.o, but its honestly not impossible. Just be wise about not overwhelming yourself and make sure to always stay ahead in your classes. Best of luck and congrats on moving to the next level!