Carbohydrates are biological molecules made of carbon, hydrogen, and oxygen in a ratio of roughly one carbon atom (
C
Cstart text, C, end text) to one water molecule (
H
2
O
H
2
Ostart text, H, end text, start subscript, 2, end subscript, start text, O, end text). This composition gives carbohydrates their name: they are made up of carbon (carbo-) plus water (-hydrate). Carbohydrate chains come in different lengths, and biologically important carbohydrates belong to three categories: monosaccharides, disaccharides, and polysaccharides.
