three carboxylic acid residues

two carboxylic acid residues and one phosphate group

one carboxylic acid residue and two phosphate groups

three phosphate groups.

Fe (II)

Co (III)

Zn (II)

Ca (II)

edible proteins

proteins with specific structure

nitrogen containing carbohydrates

carbohydrates.

$$\alpha $$-carbon of $$\alpha $$-amino acid is asymmetric.

All proteins are found in $$L$$-form

Human body can synthesise all proteins they need.

At pH = 7 both amino and carboxylic groups exist in ionised form.