Polysaccharides are a type of carbohydrate that are made of many sugar units. Polysaccharides form when many monosaccharides combine together to form substances like cellulose, starch or glycogen. All carbohydrates are made up of the elements carbon, hydrogen and oxygen. Polysaccharides are also known as complex carbohydrates because they are made up of many (sometimes thousands) sugar units. A polysaccharide such as starch is found in many of the foods we eat and is a source of energy for our body.