What are the three groups of atoms that make up amino acids called

H, - NH2 and - COOH groups

Explanation:

Lets take the example of simplest amino acid i-e Glycine

It has four functional groups:

1 - H-atom

2 - - NH2 amino group

3 - - COOH carboylic group

4 - R group

Every amino acids have same H,-NH2 and - COOH groups. The difference is in - R groups.