B4.2.1 The human digestive system


Students should be able to use the ‘lock and key theory’ as a simplified WS 1.2

model to explain enzyme action.

Students should be able to recall the sites of production and the action of amylase, proteases and lipases.

Students should be able to understand simple word equations but no chemical symbol equations are required.

Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream.

Carbohydrases break down carbohydrates to simple sugars. Amylase is a carbohydrase which breaks down starch.

Proteases break down proteins to amino acids.

Lipases break down lipids (fats) to glycerol and fatty acids.

The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.

Bile is made in the liver and stored in the gall bladder. It is alkaline to neutralise hydrochloric acid from the stomach. It also emulsifies fat

to form small droplets which increases the surface area. The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.

Recognise/draw/interpret diagrams. Translate from data to a representation with a model. Use models in explanations, or match features of a model to the data from experiments or observations that the model describes or explains. Make predictions or calculate quantities based on the model or show its limitations. Give examples of ways in which a model can be tested by observation or experiment.

Recognise and use expressions in decimal form,

Use ratios, fractions and percentages