Peroxide-laden locks

We've been studying aerobic and anaerobic bacteria in my microbiology class, the former being those that can use oxygen and the latter those that can't. Aerobes enjoy the higher energy that can be extracted from food sources in the presence of oxygen, and they've developed means to deal with the reactive (and deadly) compounds that are by-products.

One such "reactive oxygen species" is hydrogen peroxide, and catalase is an enzyme that breaks it down into water and oxygen gas. (When you put peroxide on a cut and see bubbles, they're coming from the catalase that our own cells produce. You can get the same reaction by putting peroxide on a slide smeared with bacteria that can handel oxygen. E. coli, for example.)

Researchers have now determined that the reason our hair turns gray as we age is that our bodies produce less catalase, hydrogen peroxide builds up in our hair follicles, and the pigments that give hair its color are destroyed.

[And if you read the above description carefully, you'll understand why hydrogen peroxide is only a mild antiseptic: its effects are mostly limited to those anaerobic bacteria, and they're unlikely to be sitting on surfaces where they're exposed to air. But it can kill bacteria in a cut that might become cut off from oxygen as the wound heals, and the bubbles may help clean the wound.]