Enzymes: What are they? How do they work? Conditions, Activity and Conclusions

They are essential for breathing, food digestion, muscle and nervous function, among thousands of other roles.

Enzymes help accelerate chemical reactions in the human body. They bind to molecules and alter them in specific ways.

The chemical reactions that keep us alive; our metabolism, depend on the work carried out by the enzymes.

These accelerate (catalyze) the chemical reactions, in some cases, the enzymes can generate 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 becomes products. Once the products leave the active site, the enzyme is ready to bind 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.

Replication of DNA: each cell of your body contains DNA. Each time a cell divides, that DNA must 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, use a variety of enzymes.

How enzymes work

The “lock and key” model was proposed for the first time in 1894. In this model, the active site of an enzyme is a specific form, and only the substrate will fit into it, like a lock and a key.

This model has now been updated and is called an induced adjustment model.

In this model, the active site changes shape as it interacts with the substrate. Once the substrate is completely locked and in the exact position, the catalysis can begin.

The perfect conditions:

Enzymes can only work under certain conditions. Most enzymes in the human body work best at around 37 ° C – body temperature. At lower temperatures, they will continue to work but much more slowly.

In the same way, enzymes can only work in a certain pH range (acid / alkaline). Your preference depends on where you are in the body.

For example, enzymes in the intestines work best at 7.5 pH, while enzymes in the stomach work best at pH 2 because the stomach is much more acidic.

If the temperature is too high or if the environment is too acidic or alkaline, the enzyme changes shape; this alters the shape of the active site so that the substrates can not join it; the enzyme is denatured.


Some enzymes can not work unless they have a specific non-protein molecule bound to them. These are called cofactors. For example, carbonic anhydrase, an enzyme that helps maintain the body’s pH, can not work unless it is bound to a zinc ion.


To ensure that the body’s systems function properly, sometimes the enzymes must be reduced. For example, if an enzyme is producing too much product, there must be a way to reduce or stop production.


The activity of enzymes can be inhibited in several ways:

Competitive inhibitors: a molecule blocks the active site so that the substrate has to compete with the inhibitor to bind to the enzyme.

Non-competitive inhibitors: a molecule binds to an enzyme somewhere other than the active site and reduces the efficiency with which it works.

Irreversible inhibitors: an irreversible inhibitor binds to an enzyme and permanently inactivates it.

Examples of specific enzymes:

There are thousands of enzymes in the human body, here are just a few examples:

Lipases: a group of enzymes that help digest fats in the intestine.

Amylase: helps transform starches into sugars. Amylase is found in saliva.

Maltase: also found in saliva; breaks the sugar maltose into glucose. Maltose is found in foods such as potatoes, pasta and beer.

Trypsin: is found in the small intestine and breaks down proteins into amino acids.

Lactase: also found in the small intestine, breaks lactose, sugar in milk, in glucose and galactose.

Acetylcholinesterase: breaks down the neurotransmitter acetylcholine in nerves and muscles.

Helicase:   unravel the DNA.

DNA polymerase: synthesizes deoxyribonucleotide DNA.


Enzymes play an important role in the daily functioning of the human body. By joining and altering compounds, they are vital for the proper functioning of the digestive system, the nervous system, the muscles and much, much more.