Carbohydrates are made of carbon, hydrogen, and oxygen in a ratio of 1:2:1. There are three main types of carbohydrates: monosaccharides like glucose, disaccharides formed from two monosaccharides like sucrose, and polysaccharides made of many glucose monomers like starch and cellulose. Polysaccharides can be either storage polysaccharides found in plants and animals or structural polysaccharides that provide structure.