I'm a bit anxious since I did super badly in vce chemistry - I barely met the chem study score pre req for biomed and worried that I won't be able to keep up with everyone else 
thank you so much!
Just replying to let you know I understand where you're coming from. VCE Chem was my lowest mark (got a 31 raw) and I did Chem for biomed in 1st year, just as you are. The bottom line is that Chem for Biomed is a difficult subject, but at the end of the day it's also a new slate. Obviously there will be overlap between the content, but you have to let go of your former difficulties and try to embrace it as a new experience. If you put in the work, you'll get rewarded. Simple as that.
I'd advise going over biomolecules and organic chemistry as they will be massively important. Unit 4 probably doesn't come up AS much, but ideas about gibbs free energy and spontaneity will be relevant throughout your degree. Have a glance at the subject reviews thread in this subforum for more info about the subject if you're nervous about what lies ahead.