The difference between Biological coursesWatch
Biological science is a far more broad degree, and includes plants, animals, evolution, ecosystems, genetics, etc.
Biochemistry is obviously far more chemistry heavy, and focuses on biochemical processes in humans, animals and plants. There is also a lot of molecular and cell biology.
Pharmacology/Pharmacy is the study of drugs and their effects on the body.
If you're primarily interested in disease, biomedical science would be your best option.