I did my undergraduate degree in Nutritional Science, realized I liked enzymes/protein structure a lot, and applied to a biochemistry department PhD program. I'm in my 3rd year and currently on/ahead of track so not having a biophysics background hasn't held me back.

I'd recommend, if that's what you wanted to do, to start with biophysics or molecular biology as those are the hardest aspects. A good computer science background is helpful as well, because a huge part is processing terabytes upon terabytes of micrographs into a finished, ab initio protein model. There's always room for new techniques there.

Personally, if I were to do it over, I'd major in the closest thing to biophysics/structural biology I could, and spend as much time in a lab doing undergraduate molecular biology research as I could.