The Digestive System Chapter 4

Nutrition Nutrition takes place in 5 stages Ingestion-Taking in of food Digestion-breakdown of food Absorption- into bloodstream through the small intestine Assimilation- Absorbed food enters the cells Egestion-removal of undigested food (fibre)

The main parts of the Digestive system Mouth – Where food is chewed and mixed with saliva(enzyme amylase) Oesophagus- carries food from mouth to stomach by peristalsis. Stomach- produces digestive juices. Liver- produces bile which helps in the digestion of fats. Pancreas-produces digestive enzymes. Small Intestine- absorption of food into bloodstream. Large Intestine- Water taken back into bloodstream and waste stored.

The Teeth There are 4 tooth types Incisors- Cutting and Biting Food Canine – Tearing of food Pre-molar – grinding of food Molars – grinding of food

Chemical Digestion Chemical digestion involves the use of chemicals, called enzymes, to chemically break down food. They are biological catalysts (speeds up a chemical reaction). An enzyme acts on its substrate and breaks it down into its products. Starch is broken down by the enzymes amylase and maltase to form glucose.

Experiment:To show the action of Amylase on Starch. a) Set up test tubes as shown in diagram. b) Place the test tubes in a water bath at 370 for 5 minutes

c) Remove the tubes from the water c) Remove the tubes from the water. d) To A and B add a few drops of Iodine solution e) To C and D add Benidicts solution. Result: Tube A -black blue colour is formed Tube B - no change Tube C -No change Tube D - Brick red colour is formed