There are 20 different amino acids that are commonly found in proteins. Each amino acid has a central carbon atom bonded to:

* An amino group (NH2): This group is basic.

* A carboxyl group (COOH): This group is acidic.

* A hydrogen atom (H):

* A side chain (R group): This is what differentiates the 20 different amino acids. The R group can be a simple hydrogen atom or a complex structure, and it determines the amino acid's chemical properties.

Proteins are formed by peptide bonds linking amino acids together in long chains. The order of amino acids in a protein chain is determined by the genetic code, and it dictates the protein's structure and function.