4. Enzymes

What you need to know...
  • What are enzymes?
  • Where are enzymes found?
  • What kind of reactions do enzymes help take place?
  • What biotechnology industries are enzymes used in?
In the previous topic we learnt how the code contained in DNA bases results in the production of proteins. Proteins are crucial for the functions of cells and in this topic we'll discuss the variety of proteins in cells and focus in on one particularly important group: enzymes.
Life consists of a series of complex chemical reactions. Later in this unit you will learn more about two such complex chemical reactions: respiration and photosynthesis. In order for most of the chemical reactions which take place in living things to occur they need special substances called enzymes.
Enzymes are molecules which speed up chemical reactions, without being changed in the process. Enzymes are found in every cell and are made of proteins.  Enzymes can build-up and break-down molecules.
Breaking down reactions
Make the enzyme amylase for example. This is found in your saliva and helps the breakdown of a large molecule called starch into small sugar molecules [try keeping a plain flavoured crisp in your mouth for a few minutes without swallowing and you might just be able to taste this sugar being produced by your salivary amylase]. 
We can summarise this reaction using the word equation:
We write amylase on the arrow to show that it is helping this reaction take place but is not used up in this reaction.
This diagram shows how enzymes work. 

There are a few key things you should notice:

  • Enzymes have a shape which is complementary to the substance it is helping react. This is why enzymes are specific.
  • The enzyme molecule remains unchanged as a result of the reaction - remember this is a key feature of an enzyme along with speeding up the reaction.
Building up reactions
As well as breaking down molecules, you should also know that enzymes can help make bigger molecules from smaller ones. We call these reactions "building up reactions".
Enzymes in industry
Enzymes are essential for our cells but can also be used in a range of biotechnology industries.
Do you know that enzymes are added to some washing powders? We know which washing powders have these enzymes added because they are called “biological washing powders”. The enzymes are added because of their ability to speed up breaking down reactions. Enzymes are added which help break down fat and protein stains on our clothes and make these stains easier to remove. Clever huh!
Do you know that enzymes are used to make cheese? An enzyme called rennet is used which speeds up the clotting process of milk. The solid bits (curds) are used to make cheese.