If you are going the MD or MD/PhD path (that is, the NIH's MSTP program), you will certainly have to take courses in basic/molecular biology and general/organic chemistry in order to do well on the MCATs. If you are going a PhD-only route, this is actually not necessary, even should you go into a Bio/Biomedical Engineering field. The GREs are structured far more like the SATs, and thus if you have a decent working knowledge of math up to Calculus, there should be no problems at the "quantitative" portion of the test. The verbal is basically reading comprehension, as I'm sure you're familiar with.
There do exist SAT II subject tests which are occasionally required for advanced, PURE bio/physics/math-related departments. These often require a not-insignificant background in these areas and I'd recommend that you take relevant courses if you plan on entering any of fields. The graduate department pages of any colleges' website should contain all of these prerequisites under their application requirements.
Regarding your interests, it seems like an interdisciplinary program, such as bio/biomedical engineering or neuroscience would be a good fit. Both programs, and others like them, are unbelievably vast and could meet a range of scientific interests since they leverage basically any field's specialties. In my (graduate) neuroscience interdepartmental program, we have people of many different kinds of backgrounds, psychology to physics, biology to electrical engineering. Almost all such graduate programs have introductory curricula that are designed to give you at least a basic working knowledge of the systems you'll be working on, even should there be significant gaps in your schooling re: specific subjects. It should be noted that to get any deep knowledge in an area that you're not familiar with (but required for your research), you'll spend quite a bit of time "catching up," so to speak (take it from a biology major whose work mainly consists of electrical engineering at present). But since you are just entering college, there are many opportunities to gain a lot of important background knowledge in a wide breadth of subjects - since you have talent/interest in CS but would like to work toward biological applications, I'd seriously look into any specialized/hybrid programs your university may have; some schools have entire undergrad departments devoted to highly specialized fields like cybernetics or informatics. Side note: you may be surprised at just how relevant CS is, even in "softer" fields like molecular biology ("softer" is relative to say, high energy physics). Basically everyone works with computers and code in one form or another as new methods are developed that increases the throughput of data to such a point where it is impossible to analyze without the aid of automation and clever computing strategies.
Since you are apparently an undergraduate, or soon to be one, I'd recommend that you VOLUNTEER/WORK in a lab setting. Many professors are glad to have proactive students working in their labs, and some schools offer credit for time spent working in a research lab. It also reflects very well on your chances of getting into competitive medical/graduate programs to have this experience. Even better if you go above and beyond and get some publications under your belt during this time. Additionally, reference letters are often crucial for a career in academia, and this is the single best way to have someone assess your abilities, should you want to go down this path.
Perhaps the most important factor, though, is that you become familiar with the lab environment, understand the processes by which research is performed, and really decide if this is what you want to be doing for the next couple decades. One thing I underestimated as a high school graduate is just what kind of a time commitment would be required to get these professional/terminal degrees. Granted, I was lucky and enjoy what I do immensely, but don't let it surprise you when 10 years later, you're still essentially living like a college student when all your friends have put down sizeable down payments on their lavish condos/are raising families, etc.
Don't worry though, they're miserable
EDIT: Finances. If they are a concern, and you really want that MD, an obvious plus of MD/PhD is that it will be paid for. PhD programs in the sciences are likewise, paid for. The average MD goes into debt in the range of tens, hundreds of thousands throughout the course of their education. Being a practicing physician will naturally give you some ability to pay off these loans, but if family circumstances or personal finances dictate the trajectory of your studies, this is obviously a very big plus in favor of doing a dual-degree.
EDIT 2: The MD/PhD in general could potentially be very useful if you are completely set on clinical applications of research - there are a lot of red tape to cut through when you move to human trials and having that MD could certainly expedite things. If you have no interest in practicing CLINICAL MEDICINE however (that is, being a physician of any sort), I would actually recommend that you NOT try for an MSTP program. The reason being, you will never really be at a loss for partnering with a MD with research interests, should you end up at any university with a decent teaching hospital, and even if not, long distance collaborations are both common and fruitful in today's research environment. A MD/PhD represents about 10+ years of commitment to schooling - 2 years medical school, 3-5 years of graduate studies, 2 final years of med school, and 2-10 years of residency. Best case, you pick a quick residency and a quick PhD topic and you finish in 9. Worst case, you become a resident in neurosurgery, and your PhD topic is a monkey brain-machine interface study that takes 8 years to complete - this is around 20 years of work, and you'll be 40 by the time you start doing any substantive research. Granted, you'll basically be an academic superstar, and it will be much easier to finagle grant money, getting choice academic appointments at fabulous universities, etc... but then you're 40, and you barely had any time for your personal life.
I admit, I'm kind of ignorant as far as the field goes so I may have fallen prey to some myths here and there. And I had grand visions of Osmosis Jones meets Terminator. 
lol. I think nanotechnology caught my interest because it was sort of a "comfort zone" thing: technology. However, if I actually learned more biology, I'm sure it would be more comfortable with it, too.
Been looking for a few new books to read. Too much programming mumbo jumbo, I'm going numb.
