2.32 describe an experiment to investigate the energy content in a food sample

- measure 20 cmˆ3 of water in a boiling tube and take the temperature

- weigh the mass of food and burn the food while holding it under the boiling tube

- when food has burnt out, take second temperature reading

 

2.31 describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine

Villi are in the small intestine: they are the surface through which food diffuses into the blood stream. They have thin walls (molecules can pass though easily) and increase surface area, which means the is more surface for diffusions to happen through. On the outside of the villi there are capillaries so it can directly pick up diffused food

2.30 understand that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids

Bile: is produced in the liver and stored in the gall bladder

Enzymes work best in alkaline conditions: food is acidic from being in the stomach. Bile is alkaline so when it is released into the small intestine it allows the enzymes to work (neutralizes stomach acid) Bile also emulsifies fat: give it a larger surface are which means it easier for lipases to work