How many different kinds of amino acids make up proteins?

There are 20 different common amino acids that act as the building block for proteins. Humans are able to produce 10 of the amino acids, but must obtain the other 10 through their diet.

Amino acids are the most basic building block of a protein. The twenty amino acids are: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. All amino acids contain an alpha carbon that is connected to an amino functional group, a carboxylic acid functional group, and the R-group unique to each amino acid.