Question

How are amino-acids classified?

Answer 1

Amino Acids:

Amino acids are organic molecules that are composed of an amino group and a carboxylic group with a specific side chain (R-group).

Classification of amino acids:

A. Based on R groups:

1. Amino acids can be synthesized based on the R (rest of the molecule) groups attached to their side chain.
2. R groups can be polar or nonpolar.
3. Amino acids can be called aliphatic amino acids or aromatic acids if the R group is aliphatic or aromatic respectively.
4. Amino acids can be classified on their solubility in water, if the R group is hydrophilic then the amino acid is water-soluble, or if the amino acid is hydrophobic then the amino acid is water-insoluble.
5. Every amino acid is represented as a three-letter abbreviation and a single-letter symbol.

B. Based on the ability of synthesis by organism:

a) Essential amino acids:

1. These amino acids cannot be synthesized by the body.
2. There are no special metabolic processes inside the body to synthesize essential amino acids.
3. Hence, they do need to be supplemented via diet externally.
4. There are nine such amino acids.
5. Eg, Phenylalanine, valine, threonine, tryptophan, methionine, leucine, etc.

b) Non-Essential amino acids:

1. These amino acids can be synthesized by the body.
2. There are metabolic processes inside the body to synthesize essential amino acids.
3. Hence, they do not need to be supplemented via diet.
4. Eg, Alanine, asparagine, glutamic acid, serine, etc.

c) Conditionally essential amino acids:

1. They can be synthesized by the body but can become essential amino acids due to some pathophysiological conditions.
2. Hence, they become conditionally essential and need to be supplied through diet.
3. There are six such amino acids.
4. Eg, arginine, cysteine, glycine, glutamine, proline, etc.