I wouldn't think that any university would be too bothered with what degree you had taken, as long as it had some biological/chemical relevance. For example, I've met a Sheffield grad student with a degree in Zoology. It isn't the most generic route into medicial school, but he enjoyed his degree. And I'm 99.99% sure that you'll perform better in a degree that you enjoy.
For example, if I don't get into medicine, I'll be taking a pharmacology degree. Not because I see it as the easiest route into medicine, but because I have a genuine interest in knowing how drugs work within the body. Also, if I chose not to study medicine, I would have a degree would allow me to enter other areas of science, such as the pharmaceutical industry.
So, in conclusion, do something YOU enjoy. Not a degree where you spend three/four years completing for the sake of hoping to get into medicial school.