In highschool, I loved the systematic complexity of biology and the quantitative, mechanistic focus of chemistry. The latter won out and I headed to college in Chemical Engineering, but I made the decision near the end of my freshman year to pick up Biochemistry and Molecular Biology as a second major.
Photolyase: a light-activated enzyme that repairs UV-associated DNA damage
So many times, I came within a few minutes of dropping it. The problem: molecular biology. No offense, molecular biologists, but you ran out of fresh ideas about twenty years ago. There are a finite number of ways to do PCR, and you're really scraping the bottom of the bucket at this point (and are you still enjoying all that pipetting?). I had to wade through six credits of molecular biology of increasing irrelevance before I could break into the 400-levels, and only a mild interest in microbiology kept me at it.
Finally, BMB 401 - Introduction to Biochemistry. This is the first biology course I encountered which listed organic chemistry as a prerequisite, and it made all the difference. The chemistry, the physics, the mechanistic focus, the quantitative analysis - it was all there. The Biochemistry of Metabolism pulled me in a little further, and an excellent course in Analytical Biochemistry introduced me to the good stuff: UV-Vis, NMR, EPR, Circular Dichroism, &etc. Spectroscopy uses very basic physical interactions to 'see' the unseeable, providing an amazing look into the structure and function of the molecular machines that make biology go. Those who dislike math, physics, organic and physical chemistry need not apply.
I chose to overview an experimental technique termed "Laser Flash Photolysis" for a paper and presentation project in Graduate Chemical Kinetics. It's a pretty awesome method that's already scored two Nobel prizes in chemistry (1967 and 1999) that uses ultrafast pulses of laser light to cause and 'observe' chemical reactions on the timescales at which they actually occur (nano-, pico-, and femtoseconds).
My Laser Flash Photolysis review is available here. Definitely check out the 1967 Nobel lecture on 'Immeasurably Fast Reactions' that's referenced in the review - it's a little technical, but a good read on the initial development of the technique.