- Moves food through the system
- digest the food with enzyme secretions
- absorb what has been digested
- distribute the nutrients to the blood for transport
- eliminate the waste products
Digestion is in short is about taking big things and making them smaller so that they can fit into our blood stream and finally into our cells. Enzymes are chemicals in our digestive tract that break proteins, carbohydrates into smaller and smaller units necessary for absorption.
Proteins consist of amino acids linked together. Digestion of protein involves breaking down the big, long chains of amino acids into smaller and smaller chains, so that they can get into the system.
Carbohydrates consist of glucose molecules linked together. Starch is a long-chain carbohydrate made up of many glucose molecules linked together. The larger molecules are broken down into smaller ones and eventually into a single molecule of glucose that we can absorb into the blood stream.
Fats consist of fatty acids and glycerol(triglycerides). Fat is digested when the fatty acids and the glycerol are separated, so that absorption into the blood can occur.