8Ad digestion

• proteins, fats and carbohydrates are too big for your body to use and be broken down into smaller pieces.
• digestion turns large insoluble molecules into smaller soluble molecules
• the gut and some other organs that help digestion for the digestive system
• 1. ingestion


  teeth grind food into small pieces and mix it with saliva (helps digest food and makes food easier to swallow)
• 2. food enters the gullet

  muscles in the gullet contract to make the tube above the food narrower, and this pushes food towards the stomach. Food is moved through the whole gut in the same way
• 3. stomach


  the food is churned up in the stomach with acid and more digestive juices
• 4. small intestine


  in the small intestine, more digestive juices are added and the liver adds a substance to help digest fats.
• 5. large intestine


  food we cannot digest goes to the large intestine where water is removed, which forms a more solid material called faeces
• 6. rectum


  the rectum stores faeces which are then pushes out of the anus in a process called egestion.
• bacteria in your gut feed on your food and can digest some foods that your body cannot.
• the bacteria grow and reproduce using some of these digested molecules, but the rest of the molecules can be absorbed into your body
• enzymes are substances that speed up the breaking down of large molecules into smaller ones
• substances that speed up reactions without being altered themselves are called catalysts. enzymes are biological catalysts