Have you ever wondered what the difference is between a fat that is liquid and a fat that is solid at room temperature? Let's begin by explaining why room temperature fats are solid or liquid. Fats are liquid or solid according to their chemical make up or how their building blocks are stacked together.
Protein digestion begins in the stomach with the action of an enzyme that we previously learned about called pepsin. Pepsin is the active protein-digesting enzyme of the stomach. When pepsin acts on the protein molecule, it breaks the bonds that hold the protein molecule together, called peptide bonds.
The first stage of digestion takes place in the mouth. Salivary glands located under the tongue, and in the back of the mouth, produce saliva in the mouth. Enzymes in the saliva start the chemical digestion of food. Amylase starts the breakdown of carbohydrates, while salivary lipase begins the breakdown of fats. Once the food arrives at the stomach, gastric glands secrete pepsinogen and hydrochloric acid.