Describe the process of digestion in human beings. Draw a labelled diagram of the alimentary canal.

1. 1 · Define in one line. Digestion is the breaking down of large, insoluble food molecules into small, soluble ones that the body can absorb.
2. 2 · Mouth and oesophagus. Salivary amylase breaks starch into sugar; peristalsis moves food down the oesophagus.
3. 3 · Stomach. Hydrochloric acid gives an acidic medium, pepsin digests proteins, mucus protects the lining.
4. 4 · Small intestine.
   • Bile from the liver: makes food alkaline and emulsifies fats.
   • Pancreatic juice: trypsin for proteins, lipase for fats.
   • Intestinal juice: final products are glucose, amino acids, fatty acids and glycerol.
   • Villi absorb the digested food into the blood.
5. 5 · Large intestine. Water is absorbed; waste leaves through the anus, controlled by the anal sphincter.
6. 6 · Draw the alimentary canal. [Diagram: mouth, salivary glands, oesophagus, stomach, liver, gall bladder, pancreas, small intestine, large intestine, rectum, anus]
7. 7 · Link to daily life. Chewing food well and eating fibre from vegetables and whole grains help this process.
8. 8 · Close in one line. Thus food is digested step by step and absorbed mainly in the small intestine.

Scoring tip: At each organ, name the juice, its enzyme and what it digests. A small table of organ, juice and action saves time.