At any given moment there are countless chemical reactions occurring in your body. They might be related to the digestion of your food, the contraction of your muscles, the repair or construction of new cells, the transmission of signals along your nerves, the conversion of energy to a more a useful form, or a thousand other functions.
Because they are a part of life, you might think that all of those chemical reactions occur quite easily and automatically, like the way mixing baking soda and vinegar creates bubbles of carbon dioxide gas. But in many cases, just because two molecules in your body happen to bump into each other doesn’t mean they will stick together to make another molecule that you need. That’s actually a good thing, because it gives your body a way to control those reactions.
Here’s how it works: Imagine trying to tie two ropes together by slapping them together. It’s not very likely that that will make a knot. But you can hold them together and manipulate them to make the knot. In your body, there are special chemicals that play a similar role—they hold other molecules in the right position for those molecules to stick together, causing a chemical reaction to occur. Those special chemicals are called enzymes. And enzymes are critically important to your body’s ability to manage its own functions.
If you’re tracking so far, then you might be wondering: if enzymes control chemical reactions, then what controls enzymes? There are many answers to this question; here are two examples.
When you chew food, the presence of certain substances in the food causes your salivary glands to produce an enzyme that breaks down starch (complex carbohydrate molecules) into sugar (simple carbohydrate molecules, like glucose). That’s a very important reaction for many reasons, not least because your brain needs a continuous supply of glucose to operate.
But where does the brain get glucose when you’re not eating? Part of the answer to that question is that your body can store glucose in the form of a substance called glycogen. If the glucose levels in your blood start to drop, your body produces a hormone called glucagon. Glucagon, in turn, activates an enzyme that helps break glycogen down into glucose. (Actually, it’s not quite that simple, glucagon activates an enzyme that causes a chemical reaction that activates another enzyme that activates other enzymes that actually break down the glycogen. [1] But you get the idea.)
Reference
1. Biochemistry, Glycogenolysis, National Center for Biotechnology Information Bookshelf (https://www.ncbi.nlm.nih.gov/books/NBK554417/)
