Answer: There are 20 standard amino acids found in living organisms.
Explanation: Amino acids are the building blocks of proteins. There are 20 standard amino acids found in living organisms, they are: glycine, alanine, proline, valine, leucine, isoleucine, methionine, serine, threonine, cysteine, asparagine, glutamine, phenylalanine, tyrosine, tryptophan, lysine, arginine, histidine, aspartate and glutamate. All the standard amino acids found in living organisms are alpha amino acids because they have a carboxyl group and an amino group bonded to the alpha carbon atom. The alpha carbon atom of all the standard amino acids is bonded to a carboxyl group, an amino group, an R group and a hydrogen atom except in glycine in which the R is another hydrogen atom.
