Mini Physics
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Digestion

The digestive system, enzymes and their optimum conditions, and digestive health.

  • SEC G1 Science 2027
  • 5 lessons
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Before you begin

Digestion changes large insoluble food substances into smaller soluble substances that can be absorbed.

Learning goals
  • Importance of digestion
  • Digestive organs and their functions
  • Enzyme action and optima
  • Interpreting enzyme-rate data
  • Constipation
  • Alcohol and the liver
  • Diabetes risk
Syllabus statements covered
  • explain the importance of digestion
  • identify the following main organs and associated organs of the digestive system, and state their functions: mouth, gullet, stomach, small intestine, large intestine, rectum, anus, salivary glands, pancreas, liver and gall bladder
  • show an understanding that enzymes speed up the rate of digestion and require an optimum temperature and pH to work efficiently (names of enzymes and substrates are not required)
  • interpret data on the effect of pH and temperature on the rate of digestion by enzymes
  • explain why constipation occurs and state possible preventive measures
  • state the effects of excessive alcohol consumption on the liver (e.g. damaged liver, liver cancer)
  • state how diet and level of physical activity can affect the risk of developing diabetes

Lessons

Work through them in order.

  1. Food pathway and digestive organsTrace food through the digestive system and state what each organ does.
  2. Enzymes and rate dataCompare enzyme activity at different temperatures and pH values, and distinguish the best tested condition from the exact optimum.
  3. Constipation and bowel healthExplain how fibre, fluid and movement can affect constipation risk, and connect preventive habits to bowel function.
  4. Liver health and alcoholExplain how excessive alcohol can damage the liver and increase liver-cancer risk without making either outcome certain.
  5. Understanding diabetes riskDistinguish type 1 and type 2 diabetes, and explain how diet and activity can affect type 2 diabetes risk alongside other factors.

Practise and check

Recommended nextDigestion topic check

Topic reference

Topic picture

Food pathway and the organs that supply digestive juicesSolid arrows trace food through mouth, gullet, stomach, small intestine, large intestine, rectum and anus, in that order. Dashed arrows show saliva entering the mouth from salivary glands, enzymes entering the small intestine from the pancreas, and bile moving from liver to gall bladder, then into the small intestine. Food does not pass through these four associated organs. Each organ's main function is labelled.Food follows the tube; digestive juices join itMouthChews food; saliva begins digestionGulletMuscle waves move foodStomachStores and churns foodAcid and enzymes aid digestionSmall intestineCompletes digestionAbsorbs most nutrientsLarge intestineAbsorbs remaining waterForms faecesRectumStores faecesAnusFaeces leave the bodySalivary glandsSaliva moistens foodand contains an enzymeSalivaPancreasSupplies digestive enzymesEnzymesLiverMakes bileBileGall bladderStores bile, then releases itinto the small intestineBileFood does not pass through the four associated organs.Food and its remaining materialDigestive juices
Scroll diagram horizontally to read all labels.
This is a map of functions and connections, not an anatomical drawing or a scale picture. Follow solid arrows for food and dashed arrows for digestive juices. The rectum is the final part of the large intestine; it is shown separately to identify its storage function.