Amino acids (AA) are in general any organic compounds containing carboxylic (-C00H) and amine (-NH2) functional groups. From among vast number of AAs, most important are L-alpha-amino acids - headstones of all proteins and thus key in natural sciences.

Fatty acids (FAs) are organic monocarboxylic acids. Their molecule always begins with a methyl group (-CH₃) and is terminated with a carboxylic one (-COOH). In-between there are at least 6 methylene groups (-CH₂-) and may contain one or more double bonds (-CH=CH-). Carboxylic acids with a lower carbon atom number than 8 are not considered as fatty acids.