1.1.2 Carbohydrates serve as structural elements in cell walls of plants(cellulose)or bacteria(peptidoglycans), exoskeletons of arthropods(chitin), and extracellular matrixes of vertebrate animals (proteoglycans).1.1.2 Carbohydrates serve as structural elements in cell walls of plants (cellulose) or bacteria (peptidoglycans), exoskeletons of arthropods (chitin), and extracellular matrixes of vertebrate animals (proteoglycans)