What is a protein and what functions can a protein have?

A protein molecule is a polymer which means it is built when lots of smaller molecules join together in a chain, like building blocks. These smaller molecules are called amino acids. There are are 20 different types of amino acids in our bodies so when they join together in chains there are lots of different combinations possible.This is why different types of proteins are possible. The sequence in which amino acids join together to form the protein causes the protein to fold in a certain way, giving it a unique shape. Each protein's shape is very important as it defines what the protein can actually do. There are 4 key functions a protein could have. Firstly it could act as a structural component, secondly it could act as a hormone, thirdly it could act as an antibody and finally it could act as an enzyme.