Remember we do not have those special types of cells, bacterial cells that give us the ability to break down cellulose. But certain animals, certain herbivores, for example cows, they do have those bacterial cells that produce special types of proteolytic enzymes that can cleave the bonds in cellulose to produce the individual sugars which can then be used to basically produce ATP molecules. Now, feces also contains proteins, for example proteolytic enzymes that have not been absorbed by our body that were used to basically break down the different types of macromolecules into their constituents inside our mouth, inside our stomach and inside the small intestine. Feces also contains things like bile which was produced inside the liver and was used by the small intestine to basically emulsify break down our fat gloves into smaller fat molecules. And the feces also consist of those cells that were basically scraped off of the lining of our small and large intestines and other organs in our body such as our stomach. So at the bottom of the rectum we have the structure that is known as the anus.