I'm currently in my first year of A-level Biology.
I hated all three sciences pretty much all the way through secondary until I reached y10-11 where I found a passion for Bio. Bear in mind I was probably achieving 6s at this point. I worked super hard in my final six months of y11 and got an 8 in GCSE bio, so its perfectly doable.
If you're truly interested in it you'll find the drive to work hard because, well basically, you enjoy it!
Back to your question, before y11 I didn't take anything on in bio. Through y11 I listened properly and worked through my revision topic by topic. you'll also find that the first year of bio at college, whether you take btec or a level, will be going back over GCSE stuff and adding a little more detail, so not knowing certain aspects of the GCSE course is absolutely no problem.
Just work hard and keep your passion for the subject!