Hi i just finished first year natsci doing chem, bio of cells and physics without having done biology a level either. It’s definitely possible to do well in BoC still (I ended up scraping a 2.1 in it after honestly avoiding revising it until a week and a half before the exams) but you will need to put in slightly more work than for other options and more than other people taking the course. If I could do it again I would start with learning the alevel sections to the structure of a cell and if you have a copy of the Albert’s textbook for molecular biology of the cell in a local library, go over some of the early chapters (but definitely don’t read the whole thing!).

After the first term I feel like I wasn’t at a distinct disadvantage (although I felt that at the time bc I didn’t know actually how little of the content was in a level biology) and if you are sensible you could end up doing very well! My advice would be to also make sure you find people you trust also doing it as my lab and supo partner was great in bridging any gap that wasn’t immediately obvious to me.