There are 20 amino acids commonly used to make proteins in living things. Here they are, grouped by their chemical properties:

Nonpolar, Aliphatic:

* Glycine (Gly, G)

* Alanine (Ala, A)

* Valine (Val, V)

* Leucine (Leu, L)

* Isoleucine (Ile, I)

* Proline (Pro, P)

Aromatic:

* Phenylalanine (Phe, F)

* Tyrosine (Tyr, Y)

* Tryptophan (Trp, W)

Polar, Uncharged:

* Serine (Ser, S)

* Threonine (Thr, T)

* Cysteine (Cys, C)

* Asparagine (Asn, N)

* Glutamine (Gln, Q)

Polar, Charged, Acidic:

* Aspartic acid (Asp, D)

* Glutamic acid (Glu, E)

Polar, Charged, Basic:

* Lysine (Lys, K)

* Arginine (Arg, R)

* Histidine (His, H)

Note: While there are over 500 amino acids found in nature, these 20 are the standard building blocks of proteins in living organisms.