So when we eat the proteins, when the proteins into the oral cavity of our mouth, we begin the process of mechanical digestion. That simply means we increase the surface area of the protein by breaking down our food. Now, mechanical digestion does not mean chemically breaking our bonds. Chemical digestion of proteins begins within the stomach. So within the stomach, we have specialized types of cells known as chief cells, that secrete a protein enzyme known as pepsin. And pepsin is responsible for cleaving chemical bonds on proteins.