Why are so many proteins able to be made from so few exons?

Answer 1

It might be just a guess, but there's a certain amount of amino acids that exist. Proteins are basically combinations of different amino acids. Considering there are a huge variety of different combinations the amino acids can make, it's not surprising there are more proteins than amino acids.

For example:

1, 2, 3, 4 form protein 1
2, 3, 1, 4 form protein 2
4, 2, 1, 3 form protein 3

Just a bunch of combinations.

Answer 2

There are multiple structures to a protein. There is the Primary structure, which includes the order of amino acids. Whilst there may not be that many amino acids (so far 22 are known), polypeptides can be thousands of amino acids in length. Hence even if you only had two different kinds of amino acids, the combinations you can conjure are infinite. Secondary structure is then the pleating or coiling of this primary structure, and tertiary structure is the folding of this polypeptide to form a three-dimensional form. Then quaternary structure involves multiple polypeptides bonding to form a PROTEIN. Thus not only is there significant variation in forming the polypeptide itself, but there can also be different combinations of these amino acid chains. After this the protein can be cleaved and altered to make it more functional. Hence, despite few nucleotides and amino acids, you can have many proteins.