Sugars, starches, and structural fibers
Primary fuel and structural material
Carbohydrates are molecules built from carbon, hydrogen, and oxygen, typically in a 1:2:1 ratio. Monosaccharides such as glucose are the cell's primary energy currency, fueling glycolysis and cellular respiration. Polysaccharides such as glycogen (in animals) and starch (in plants) serve as compact energy stores, while cellulose provides structural rigidity in plant cell walls. Carbohydrates also contribute to cell-surface recognition and signaling.