KS3 Digestion

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Year 8 Digestion Learning Objectives

Pupils should be able to:

  • recall the three food groups- proteins, fats and carbohydrates.
  • identify the main food tests: starch – iodine solution goes black-blue, glucose – Benedict’s + heat gives orange precipitate, fat dissolves in ethanol then milky emulsion with water, protein – purple solution with Biuret’s + Sodium Hydroxide.
  • recall the concept of a balanced diet.
  • know that feeding consists of ingestion, digestion, absorption and egestion.
  • explain that starch, protein and fat molecules are digested into smaller soluble molecules so that they can be absorbed into the blood.
  • identify the structure of teeth and jaws and their specialisms.
  • know that chewing, tongue action and saliva all help to break up food physically.
  • know that saliva wets food and has the enzyme amylase to start the chemical digestion of starch to maltose.
  • identify that peristalsis is the controlled pushing of food through the gut.
  • identify that stomach acid kills germs and provides a low pH for the enzyme pepsin in gastric juice which helps to break down proteins chemically.
  • identify that muscular churning of the stomach helps with the physical breakdown.
  • identify that in the duodenum, further chemical digestion starts.
  • know that pancreatic juice, from the pancreas, is secreted into the duodenum and that it contains protease, carbohydrates and lipase enzymes and sodium carbonate to help neutralise stomach acid.
  • know that bile from the liver is stored in the gall bladder.
  • know that bile is use in the duodenum to emulsify fats and help neutralise acid.
  • know that the ileum has a multi-folded surface of villi which have microvilli .  This increases the surface area for absorption and there is an excellent blood supply for transport.
  • know that the large intestine reabsorbs water from waste into the blood.
  • know that the rectum stores faeces for egestion via the anus.
  • know the role of an enzyme.
  • explain the structure of an active site in terms of its specificity.
  • explain the term denaturing in terms of the effect of temperature and pH on the active site.

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