Final answer:
Proteins are made up of amino acids, and their diversity is due to the different ways in which these amino acids can be combined.
Step-by-step explanation:
Proteins are made up of units called amino acids. Despite there being only 20 common amino acids, they can be combined in many different ways to form thousands of unique proteins. The number and order of amino acids determine the shape and function of a protein. This diversity allows proteins to perform a wide range of vital functions in living organisms.