When you look at a plant or an animal, be it a majestic redwood, your golden retriever, or even another person, you see the entire organism, a smoothly functioning whole.

But beneath the surface is a living machine. At scales much too small for us to see with the naked eye, there are chemical reactions going on that enable organisms to live. For example, when you eat, proteins called enzymes help speed up the chemical reactions that break down food so that you can get the energy you need to live. If you major in biochemistry, you’ll examine these and other chemical reactions.