Cellulose and starch are two similar polymers, but the main difference between them is humans can eat starch but are not able to digest cellulose. Humans have enzymes that break down starch into glucose that the body uses as fuel, but the body has no enzymes that break down cellulose.
Some animals, such as termites, which eat wood, have the enzymes needed to break down cellulose. Starch is a carbohydrate mainly found in plants, such as potatoes and cereal grains. Cellulose is also found in plants and is an organic compound. It is the supporting part of plants such as the stems of flowers or the wood of trees. Cellulose is a lot stronger than starch and is used to make fibers such as rope and clothing.
Unlike cellulose, starch is soluble in water, so it is useless as a material. Cellulose and starch are made from the same monomer and have the same glucose-based repeat units. However, cellulose's glucose repeat units are rotated 180 degrees around the axis of the polymer backbone chain relative to the last repeat unit. Starch glucose repeat units are all in the same direction. The glucose units in starch are referred to as alpha linkages, and the glucose units in cellulose are referred to as beta linkages.