With respect to amino acids, what does the term radical stand for?

Question

With respect to amino acids, what does the term radical stand for?

Answer 1

Every aplha-amino acid is a carboxylic acid, which has an amino group at the second carbon atom after the C of the COOH. That is called alpha position of the amino group. So an alpha amino acid has a general formula:

H2N-CH(R)-COOH

And R stands for radical (substituent). It is diferent for every amino acid. For Glycine it is H, for alanine -CH3 and so on.