I studied biology A level, I needed to get an A in it for my uni course and though I got there in the end I found it quite a tough A level actually. It all depends on you as an individual though, I think it is possible but I wouldn't have been able to do it all in one year and I think it would be tough. Its easy to screw up if you don't quite get how to hit the marks in the exams and I managed to jump from a C to an A in one of my modules just by getting the knack of doing the actual exam papers (before then I'd stupidly avoided past exam papers...out of fear or something I think!)