What are proteins ?

They are large molecules made by joining many amino acids together by peptide bonds so that a long chain (with no branches) is made.

Inside our bodies, each protein is made of a chain containing a sequence made of the 20 naturally occurring amino acids - see what these molecules look like here

This chain can twist and fold in many different ways because the amino acids have chemical groups sticking out from them which can attract eachother.  So the final chain of amino acids can sometimes fold up into a ball, or be long and fibrous.  

See the different levels of protein structure here

The shape, or in scientific language, the conformation of the protein will let it do different things in our cells and in our body.

For example, enzymes , which are biological catalysts, are globular, whereas hair (which is made out of the protein called keratin) is fibrous. 

If the shape of the protein changes, it may no longer do its job - it has been denatured .  This is bad, so anything that denatures proteins, such as heating or changing the pH, should be avoided if the cell is to stay alive.

A lot of foods contain proteins - meat, fish, eggs, milk and even some plants such as peas and beans - and we need to eat such food every day because our body cannot store proteins.

Action:

When we cook, we denature proteins in the food - what happens to the structure (think of the white of an egg before and after you have boiled the egg!)

Can you think of more cooking examples of denaturation of proteins?

When we heat our food for a long time we denature the enzymes of any microorganisms living in the raw food - so that they are killed!  Now it is safe to eat!

See plenty of activities and lesson plans for protein kitchen science here!