And whenever we want to form ATP molecules, we can break down glycogen into the individual glucose constituents and then we can feed those glucose molecules into the metabolism cycle glycolysis to basically form ATP molecules. Now, certain organisms, such as plants, as we'll see in just a moment, also use polysaccharides to basically form structure, give the cell structure and protection. Now, those polysaccharides that consist entirely of the same identical type of monosaccharide, these polysaccharides are known as homopolymers. And this is what we're going to focus on in this lecture. We're going to begin by discussing glycogen, which is the major type of polysaccharide that exists in our own cells and other animal cells. And then we're going to move on and discuss starch as well as cellulose.