6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Learn this properly: Principles of OrganisationThe small intestine is the main site where the soluble products of digestion are absorbed into the blood. Its inner surface is folded into millions of finger-like villi.
Explain how the structure of the small intestine is adapted for the efficient absorption of digested food. (6 marks)
A student investigated how temperature affects the activity of the enzyme amylase, which breaks down starch. They measured the time taken for amylase to fully digest a fixed amount of starch at five temperatures, then calculated the rate of reaction.
| Temperature / °C | Time to digest starch / s | Rate of reaction / s⁻¹ |
|---|---|---|
| 10 | 200 | 0.0050 |
| 20 | 100 | 0.0100 |
| 30 | 50 | 0.0200 |
| 40 | 40 | X |
| 60 | no reaction | 0.0000 |
(a) The rate of reaction is calculated using rate=time1. Calculate value X (the rate at 40 °C). Give your answer to 3 significant figures. (2 marks)
(b) Explain, in terms of the enzyme, why there was no reaction at 60 °C. (2 marks)
Humans have a double circulatory system. The wall of the left ventricle is much thicker than the wall of the right ventricle.
(a) Name the blood vessel that carries blood away from the left ventricle. (1 mark)
(b) Explain why the wall of the left ventricle is thicker than the wall of the right ventricle. (2 marks)
In coronary heart disease (CHD), layers of fatty material build up inside the coronary arteries.
(a) Explain how a build-up of fatty material in the coronary arteries can lead to a heart attack. (2 marks)
(b) A stent is one possible treatment. State how a stent treats a narrowed coronary artery. (1 mark)
Gas exchange in the lungs takes place across the alveoli.
Describe two ways in which the alveoli are adapted to allow efficient gas exchange, and explain how each adaptation helps. (2 marks)
In a plant, water is transported from the roots to the leaves through one type of transport tissue, and dissolved sugars are transported around the plant through another.
Name the tissue that transports water from the roots to the leaves. (1 mark)