Biology

Amino acids

Amino acids are the building blocks of proteins, and each has its own structure and chemical designation. As their name implies, the one thing amino acids have in common chemically is the NH2 (amino), CO2H (acid) groups.

Some amino acids are produced in the body as intermediates of metabolic processes, whereas half of the amino acids are essential - meaning that they are obtained from dietary proteins. Amino acids are not stored for later use, so a proper diet always contains a steady supply of essential amino acids. On the other hand, plants are capable of producing all of the amino acids they require.

Proteins are metabolized, or broken up, in the body into their component amino acids, which are then used to make other proteins or chemically altered to participate in other reactions within the body.

What are amino acids?

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The 20 amino acids used in the human body

Essential	Non-essential
Methionine (Met, M)	Glycine (Gly, G)
Valine (Val, V)	Cysteine (Cys, C)
Lysine (Lys, K)	Alanine (Ala, A)
Leucine (Leu, L)	Proline (Pro, P)
Arginine (Arg, R)	Aspartic acid (Asp, D)
Isoleucine (Ile, I)	Glutamic acid (Glu, E)
Histidine (His, H)	Serine (Ser, S)
Phenylalanine (Phe, F)	Asparagine (Asn, N)
Tryptophan (Trp, W)	Tyrosine (Tyr, Y)
Threonine (Thr, T)	Glutamine (Gln, Q)

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Quick Facts

Role in the human body: Protein synthesis

More than 50 known amino acids, but only a total of 20 used in the human body (10 are essential amino acids, 11 if phenylalanine is deficient because it is used to make tyrosine)

Standard formula is NH2-CH-CO2H-R, where R is the differentiating functional group or side chain

Branched chain amino acids are important for skeletal muscle

Errors in amino acid metabolism result in disease, such as phenylketonuria

The basic amino acids can be chemically modified to other amino acids, such as homocysteine and ornithine.