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.
The wall of the small intestine is folded and covered in millions of tiny finger-like projections called villi. Each villus has a wall that is only one cell thick, a rich supply of blood capillaries, and (inside) a lacteal.
Explain how the small intestine is adapted for the efficient absorption of the products of digestion into the blood. (6 marks)
A student investigated how pH affects the activity of the enzyme amylase, which breaks down starch. The student mixed amylase with starch at five different pH values and measured the time taken for all the starch to be broken down (tested using iodine solution). The results are shown below.
| pH | Time for starch to be broken down / s |
|---|---|
| 4 | 240 |
| 5 | 150 |
| 6 | 60 |
| 7 | 90 |
| 8 | 200 |
(a) State the optimum pH for this amylase, and justify your answer using the data. (2 marks)
(b) Explain, in terms of the enzyme's shape, why the starch was broken down very slowly at pH 4. (2 marks)
The heart pumps blood around the body through three types of blood vessel: arteries, veins and capillaries.
(a) Arteries have a thick wall containing a lot of muscle and elastic tissue. Explain how this structure is related to the function of arteries. (2 marks)
(b) Give one structural feature of a vein, other than wall thickness, that is related to its function. (1 mark)
A student carried out food tests on an unknown food sample.
(a) Name the reagent used to test for protein, and state the colour change seen if protein is present. (2 marks)
(b) The student also tested for reducing sugars using Benedict's solution. State what the student must do, other than adding the reagent, for this test to work. (1 mark)
In coronary heart disease, layers of fatty material build up inside the coronary arteries.
Explain how this build-up of fatty material can lead to a reduced supply of oxygen to the heart muscle. (2 marks)
Water is lost from the leaves of a plant by transpiration.
Name the small openings in the lower epidermis of a leaf through which water vapour is lost. (1 mark)