AQA A-Level Biology: Paper 3 2019
1.1 Describe how ultrafiltration occurs in a glomerulus. - correct answer-- High hydrostatic
pressure.
- Small substances (such as water and glucose) pass out through small gaps in the capillary
endothelium.
2.1 Describe the role of saprobionts in the nitrogen cycle. - correct answer-- Use enzymes to
decompose proteins.
- They release ammonium.
2.2 One environmental issue arising from the use of fertilisers is eutrophication.
Eutrophication can cause water to become cloudy.
You are given samples of water from three different rivers.
Describe how you would obtain a quantitative measurement of their cloudiness. - correct
answer-- Use a colorimeter,
- To measure the absorbance of light.
- Make sure the experiment is standardised by ensuring you have the same volume of water
and zeroing the colorimeter before use.
3.1 Name valve A and chamber B. - correct answer-Valve A: Left Atrioventricular.
Chamber B: Left Ventricle.
3.2 Give two safety precautions that should be followed when dissecting a heart. - correct
answer-1) Use a sharp scalpel.
2) Disinfect the equipment.
3.3 Explain how valve A in Figure 2 maintains a unidirectional flow of blood. - correct
answer-- When the pressure above the valve is higher than below the valve, it opens.
- And when the pressure below the valve is higher than above, the valve closes.
3.4 Caffeine affects the autonomic nervous system.
Suggest how caffeine could account for the results of Group I in Figure 3 at 60 minutes. -
correct answer-- More action potentials along the sympathetic nervous system branch,
- To SAN increasing the heart rate.
3.6 The increase seen in Group I could be due to the combination of caffeine and sugar.
Suggest one drink to be given to an additional group that should be investigated to find out if
this is true.
Give a reason for your answer. - correct answer-- The group should be given a sugar
solution only,
1.1 Describe how ultrafiltration occurs in a glomerulus. - correct answer-- High hydrostatic
pressure.
- Small substances (such as water and glucose) pass out through small gaps in the capillary
endothelium.
2.1 Describe the role of saprobionts in the nitrogen cycle. - correct answer-- Use enzymes to
decompose proteins.
- They release ammonium.
2.2 One environmental issue arising from the use of fertilisers is eutrophication.
Eutrophication can cause water to become cloudy.
You are given samples of water from three different rivers.
Describe how you would obtain a quantitative measurement of their cloudiness. - correct
answer-- Use a colorimeter,
- To measure the absorbance of light.
- Make sure the experiment is standardised by ensuring you have the same volume of water
and zeroing the colorimeter before use.
3.1 Name valve A and chamber B. - correct answer-Valve A: Left Atrioventricular.
Chamber B: Left Ventricle.
3.2 Give two safety precautions that should be followed when dissecting a heart. - correct
answer-1) Use a sharp scalpel.
2) Disinfect the equipment.
3.3 Explain how valve A in Figure 2 maintains a unidirectional flow of blood. - correct
answer-- When the pressure above the valve is higher than below the valve, it opens.
- And when the pressure below the valve is higher than above, the valve closes.
3.4 Caffeine affects the autonomic nervous system.
Suggest how caffeine could account for the results of Group I in Figure 3 at 60 minutes. -
correct answer-- More action potentials along the sympathetic nervous system branch,
- To SAN increasing the heart rate.
3.6 The increase seen in Group I could be due to the combination of caffeine and sugar.
Suggest one drink to be given to an additional group that should be investigated to find out if
this is true.
Give a reason for your answer. - correct answer-- The group should be given a sugar
solution only,
