Enzymes

Enzymes are biological catalysts, meaning they speed up the chemical reactions in cells without being used up in the process.
Made up of proteins, enzymes have a complex three-dimensional structure which is vital for their function.
Every enzyme has an active site, which is a region where specific molecules can attach.
These specific molecules are named substrates, and they fit into the enzyme’s active site like a ‘key in a lock’.
Enzymes are often specific, meaning they will only catalyse certain reactions due to the unique shape of their active site.

How Enzymes Work

An enzyme and its substrate come together to form an enzyme-substrate complex.
Once the substrate is attached to the enzyme, the enzyme starts the reaction.
The reaction takes place rapidly, then the products of the reaction are released.
The enzyme itself remains unchanged and is then available to catalyse more reactions.

Several factors can influence the rate at which enzymes work including: temperature, pH, and substrate concentration.
A rise in temperature usually increases enzyme activity up to an optimal temperature, beyond which, the enzyme may begin to lose its shape and negatively affect their function. This state is known as denaturation.
The pH also affects enzyme activity. Most enzymes function best at a specific pH, a deviation from which can reduce their activity.
Enzyme activity increases as substrate concentration increases, up to a point. Once all the active sites are full, the enzyme is working at its maximum rate and increasing substrate concentration further will have no effect.

Some molecules can inappropriately bind to an enzyme’s active site and prevent it from binding to its substrate, these are known as inhibitors.
Competitive inhibitors fit into the enzyme’s active site and compete with the substrate for admission.
Non-competitive inhibitors bind somewhere else on the enzyme and distort its shape, making it impossible for the substrate to fit into the active site.
Some inhibitors are permanent, they bind and never detach - destroying the enzyme’s functionality indefinitely. Others are temporary, attaching and detaching without causing permanent harm.

Enzymes are crucial in digestion as they help to break down the food we eat into smaller molecules that can be absorbed into the bloodstream.
Some common digestive enzymes include amylase, which breaks down starch into sugars, protease, which breaks down proteins into amino acids, and lipases, which break down fats into fatty acids and glycerol.