Pectin, which is responsible for the firmness and softness of fruits, is mainly composed of which acid unit?

Explanation

Pectin is a family of plant polysaccharides rich in D-galacturonic acid residues, including partially methyl-esterified chains. It contributes to fruit cell-wall properties and texture. Aspartic and glutamic acids are amino acids, and lactic acid is not the principal pectin unit.