Enzymes help speed up chemical reactions in the human body. They bind to molecules and alter them in specific ways. They are essential for respiration, digesting food, muscle and nerve function, among thousands of other roles.

In this article, we will explain what an enzyme is, how it works, and give some common examples of enzymes in the human body.

Contents of this article:

The basics

Alpha amylase enzyme
The enzyme amylase (pictured), breaks down starch into sugars.

Enzymes are built of proteins folded into complicated shapes; they are present throughout the body.

The chemical reactions that keep us alive – our metabolism – rely on the work that enzymes carry out.

Enzymes speed up (catalyze) chemical reactions; in some cases, enzymes can make a chemical reaction millions of times faster than it would have been without it.

A substrate binds to the active site of an enzyme and is converted into products. Once the products leave the active site, the enzyme is ready to attach to a new substrate and repeat the process.

What do enzymes do?

The digestive system – enzymes help the body break down larger complex molecules into smaller molecules, such as glucose, so that the body can use them as fuel.

DNA replication – each cell in your body contains DNA. Each time a cell divides, that DNA needs to be copied. Enzymes help in this process by unwinding the DNA coils and copying the information.

Liver enzymes – the liver breaks down toxins in the body. To do this, it uses a range of enzymes.

How enzymes work

Enzyme lock and key model
Enzyme lock and key model

The “lock and key” model was first proposed in 1894. In this model, an enzyme’s active site is a specific shape, and only the substrate will fit into it – like a lock and key.

This model has now been updated and is called the induced-fit model.

In this model, the active site changes shape as it interacts with the substrate. Once…