Physical digestion, also called mechanical digestion, is the process where food is physically broken down into smaller pieces by actions such as chewing, grinding, churning, and squeezing. This process increases the surface area of food, making it more manageable and easier for enzymes to act on. It does not change the chemical structure of the food. Examples include chewing in the mouth and muscular churning in the stomach. Chemical digestion, on the other hand, involves breaking down the complex molecules in food into smaller, absorbable molecules through enzymatic reactions. This process changes the chemical structure of the food by breaking chemical bonds. It begins in the mouth with enzymes in saliva and continues in the stomach and small intestine, where various enzymes and digestive juices further break down carbohydrates, proteins, and fats into their basic building blocks like sugars, amino acids, and fatty acids for absorption. In summary, physical digestion is the mechanical breakdown of food without chemical change, while chemical digestion involves enzymatic reactions that alter the food's chemical composition to enable nutrient absorption.
