Starch,

Common name applied to a white, granular or powdery, odorless, tasteless, complex carbohydrate, (C6H10O5)x, abundant in the seeds of cereal plants and in bulbs and tubers. Molecules of starch are made of hundreds or thousands of atoms, corresponding to values of x, as given in the formula above, that range from about 50 to many thousands.

The digestion of starch in the human body follows this course: The hydrolysis begins in the mouth under the action of salivary ptyalin, but is completed in the small intestine. The body does not use immediately all the glucose absorbed from the digestion of starch, but converts much of it to glycogen, which is stored in the liver. (Glycogen, called animal starch, has a structure nearly identical with that of amyl pectin.) As the body requires glucose, hydrolysis of glycogen releases it into the bloodstream. Glycogen provides, therefore, an energy reserve for animals in the same way that ordinary starch does for plants.