I am an undergraduate student pursuing a B.Sc(Hons.) degree in Physics. I want to pursue an academic career in Biophysics. So, I wanted to know which subjects are required for higher studies in Biophysics. In my course, we get to choose one ancillary subject for the first two semesters, then another ancillary subject for the next two semesters. The final two semesters are fully focused on Physics. I am about to complete my second semester, and I took up Mathematics as my ancillary subject. Now, I need to choose between Chemistry, Computer Science or Microbiology for the next two semesters, and I am not sure which one to choose. Microbiology is looking like the obvious choice but I think that knowledge of Chemistry and Computer Science is also going to have applications in Biophysics. So could you help me out by telling me which one of these subjects would be most beneficial in learning, keeping in mind that I want to pursue Biophysics in the future?
Specific biological domain knowledge will be something that you will learn in the course of doing research, and can be hard to predict at this point in your studies, because you have no idea what kind of graduate program you'll be admitted to or the specific research field of your prospective advisor.
Therefore, while all of those directions sound fine and won't be wasted if you choose them, I would lean towards the more foundational topics, i.e. Chemistry or Computer Science, that you could use no matter what direction you took in the future. Another option would be statistics, since nearly any biophysics research involving experiments will need a very solid understanding of stats to design experiments with high statistical power, and to make sense of the resulting data without getting tricked by spurious correlations.
Though I've commented that this question should be moved to https://physics.stackexchange.com/, I'll point out that all of these options are fine. Personally, I think a lot of the really exciting current work in biophysics intersects microbiology, but I am perhaps biased in that this is what my lab works on! I will also note that computational skills are extremely valuable (for experimentalists as well as theorists).
Assuming you were seeking to get your biophysics PhD in a physics department in the US, none of the subjects you listed are essential. It would be very important to complete a physics major with good grades in physics subjects. Research experience would also be very helpful. Math/chemistry/computer science/biology would all be helpful, but none of them stand out as more important than the others. I might suggest statistics/computer science because those are subjects that many biologists might not have studied or wish to practice, and therefore they might appreciate your skills.
After you complete your PhD, your undergraduate coursework will not be scrutinized much by employers. You should have learned many skills that are not included in the undergraduate curriculum before you finish your PhD.
If you have scholarship money, financial aid money, or money to pay for extra classes, you don’t have to pick and choose. You can take all those courses if they interest you but not all of them will go towards your degree. Your objective is to get your degree and I also see your desire to learn the most valuable information. Please go to your counselor and express this. I hope this provides some insight.
Check if your department has an undergraduate course coordinator - a person who's supposed to help undergraduates choose courses. He or she would be the person best-positioned to answer your questions, especially since the courses you should take depends on what your department offers in the first place.
If your department does not have an undergraduate course coordinator, ask your biophysics professor(s) instead.