A-level
BIOLOGY
Paper 1
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Answer all questions in the spaces provided. box

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. | 1  | Describe how a non-competitive inhibitor can reduce the rate of an
enzyme-controlled reaction.
[3 marks]
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Pectin is a substance found in some fruit and vegetables.
A scientist investigated the effect of pectin on the hydrolysis of lipids by a lipase
enzyme.
His results are shown in Figure 1.
Figure 1box

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. | 2  | The scientist concluded that pectin is a non-competitive inhibitor of the lipase enzyme.
Use Figure 1 to explain why the scientist concluded that pectin is a non-competitive
inhibitor.
[1 mark]
Question 1 continues on the next page
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The scientist also found that pectin stops the action of bile salts. He prepared two
suspensions:
• suspension A – lipid and bile salts
• suspension B – lipid, bile salts and pectin.
He did not add lipase to either suspension.
He observed samples from the suspensions using an optical microscope.
Figure 2 shows what he saw in a typical sample from each suspension.
Figure 2box

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. | 3  | Calculate the maximum length of the large lipid droplet marked X in Figure 2.
Using a ruler with millimetre intervals always includes an uncertainty in the
measurement. Use the uncertainty in your measurement to determine the uncertainty
of your calculated maximum length.
You can assume there is no uncertainty in the magnification.
[2 marks]

Maximum length =  | µm

Uncertainty of your calculated maximum length =  | µm
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. | 4  | No large lipid droplets are visible with the optical microscope in the samples from
suspension A.
Explain why.
[2 marks]box
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. | 1  | Table 1 shows cell wall components in plants, algae, fungi and prokaryotes.
Complete Table 1 by putting a tick () where a cell wall component is present.
[3 marks]
Table 1

Cell wall
component  | Plants  | Algae  | Fungi  | Prokaryotes
Cellulose
Murein
Chitinbox
Cell walls make up much of the fibre that people eat.
Scientists investigated the relationship between the mass of fibre people ate each day
and their risk of cardiovascular disease (CVD).
They gathered data from a large sample of people and used this to calculate a relative
risk.
• A relative risk of 1 means there is no difference in risk between the sample and the
whole population.
• A relative risk of < 1 means CVD is less likely to occur in the sample than in the
whole population.
• A relative risk of > 1 means CVD is more likely to occur in the sample than in the
whole population.
Their results are shown in Figure 3. A value of ± 2 standard deviations from the mean
includes over 95% of the data.
Figure 3
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. | 2  | A student concluded from Figure 3 that eating an extra 10 g of fibre per day would
significantly lower his risk of cardiovascular disease.
Evaluate his conclusion.
[4 marks]
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. | 3  | The scientists estimated the mean mass of fibre eaten per day using a food frequency
questionnaire (FFQ).
The FFQ asks each person how often they have eaten many types of food over the
past year.
An alternative method to calculate fibre eaten is for a nurse to ask each person
detailed questions about what they have eaten in the last 24 hours.
Suggest one advantage of using the FFQ method and one disadvantage of using the
FFQ method compared with the alternative method.
[2 marks]
Advantage
Disadvantagebox
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ANSWER IN THE SPACES PROVIDED
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*10* IB/M/Jun19/7402/1
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0 | 3  | A group of students investigated biodiversity of different areas of farmland.
They collected data in each of these habitats:
• the centre of a field
• the edge of a field
• a hedge between fields.
Their results are shown in Figure 4.
Figure 4box

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. | 1  | What data would the students need to collect to calculate their index of diversity in
each habitat?
Do not include apparatus used for species sampling in your answer.
[1 mark