AS & A Level Biology - 9700 Paper 2 2015 Winter Zone 2

A student compared an image of a plant cell with an image of an animal cell. Both images were at the same magnification.

Parts (a) to (c) are four correct comparative statements about these images.

(a) Both cells contain large numbers of an organelle, bound by a double membrane. The inner membrane of these organelles is folded. These organelles all have a similar structure but do not always appear to have the same shape.

(i) State the name of the organelles described.
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(ii) Suggest one reason why the organelles described do not always seem to have the same shape.
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(b) Both cells contain cell structures that are approximately 25nm in diameter and are not bound by a membrane.

(i) State the name of the cell structures described.
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(ii) Draw a circle around the measurement that has the same value as 25nm.
0.00025μm 0.0025μm 0.025μm 0.25μm 2.5μm
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(c) There are strands of cytoplasm passing through channels in the cell wall of the plant cell. These are not visible in the animal cell.

(i) State the name of the cell structures described.
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(ii) Explain one advantage to the plant cell of having these structures.
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Tobacco smoking is known to be associated with atherosclerosis and emphysema.
(a) Outline ways in which tobacco smoking can contribute to atherosclerosis.
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(b) Fig. 2.1 is a scan of the lungs of a person with emphysema. One common feature in the
damaged areas labelled is a loss of the elastic fibres of the alveoli. Another feature is an
increased number of macrophages and neutrophils.



(i) State the general role shared by macrophages and neutrophils.
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(ii) Suggest how the loss of the elastic fibres would cause the enlargement of the lung shown
in Fig. 2.1.
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(c) The synthesis and release of elastase enzymes by macrophages and neutrophils is an
important feature in the development and progression of emphysema. Elastase causes the
breakdown of the protein elastin, the main component of elastic fibres.

(i) Explain what is meant by an enzyme.
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(ii) Elastase has an active site with a specific shape. The mode of action of this enzyme
supports the lock and key hypothesis.
Explain the mode of action of elastase.
You may use the space below to draw a diagram or diagrams to help your answer.
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(d) There are two inhibitors of elastase that are produced in the body, TIMP-1 and A1AT:
• macrophage elastase is inhibited by TIMP-1
• neutrophil elastase is inhibited by A1AT.
The inhibitors can be inactivated by the elastase enzymes:
• macrophage elastase can inactivate A1AT
• neutrophil elastase can inactivate TIMP-1.
In healthy lungs, the activity of elastase enzymes is regulated. Tobacco smoke can disrupt
this regulation.

(i) One effect of tobacco smoke is to cause changes in the structure of A1AT, a competitive
inhibitor.
Suggest how structural changes to A1AT will affect its mode of action.
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(ii) A1AT is a protein. Some non-smokers have a mutation in the gene coding for A1AT and
are at risk of developing emphysema as there is a lack of A1AT in the lung tissue.
Explain why a lack of A1AT in these non-smokers means that they are at risk of developing
emphysema.
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(e) Tobacco smoke is known to cause increased production of macrophage elastase. $MMP12$ is
the gene coding for macrophage elastase. Copies of this gene are produced as messenger
RNA (mRNA).
Describe how this mRNA is used in translation to produce macrophage elastase.
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(a) Name stages A and C.
A ............................................................
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(b) Put stages K to N in the correct sequence, starting with the stage that immediately follows stage C.
C ⟶ .......... ⟶ .......... ⟶ .......... ⟶ .......... [1]

(c) Explain how the behaviour of the chromosomes and spindle during stage L in Fig. 3.1 ensures that the two daughter cells will be genetically identical.
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(a) Table 4.1 describes three examples of substances moving into or out of cells.

Complete Table 4.1 by identifying the transport mechanism involved for each example.

[Table_4.1]

| example | transport mechanism involved |
|------------------------------------------------------------------------------------|-----------------------------|
| uptake of magnesium ions from a lower concentration in the soil solution to a higher | |
| concentration in the cytoplasm of a root hair cell | |
| release of antibodies from an active B-lymphocyte (plasma cell) | |
| movement of sucrose from a companion cell into a phloem sieve tube element via | |
| plasmodesmata | |

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(b) Oxygen moves into and out of red blood cells. Fig. 4.1 shows an oxygen dissociation curve for adult human haemoglobin.

[Fig. 4.1]

The steepest part of the curve is between 2.6kPa and 4.2kPa.
Explain the importance of this for respiring tissues.
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(a) Explain the difference between an infectious and a non-infectious disease. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. [2]

Malaria is an infectious disease caused by Plasmodium. Plasmodium requires two hosts to complete its complex life cycle. One of the hosts is the Anopheles mosquito, which acts as a vector of malaria.
Transmission of malaria occurs when females of some species of Anopheles take blood meals from humans infected with Plasmodium, and then feed on uninfected individuals.
Both male and female Anopheles mosquitos have piercing and sucking mouthparts. The female mosquito is shown in Fig. 5.1.

(b) The blood meals are a good source of protein for Anopheles for the production of eggs.
Explain why blood is a good source of protein.
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(c) Fig. 5.2 shows the global distribution of those species of Anopheles that are able to act as hosts for Plasmodium.
(i) Describe and explain the difference between the global distribution of Anopheles shown in Fig. 5.2 and the global distribution of malaria. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. [3]
(ii) The distribution of Anopheles shown in Fig. 5.2 includes over forty different species that are vectors of malaria. The areas with the highest number of cases of malaria are also the areas where Anopheles gambiae occurs. A. gambiae is responsible for most of the transmission of the disease in these areas.
Suggest why A. gambiae is responsible for most of the transmission of Plasmodium. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. [3]
(d) Fig. 5.3 is part of a complex food web in an area of Kenya where the larvae and adults of A. gambiae occur.
(i) Name one organism in Fig. 5.3 that is a tertiary consumer. ............................................................................................................................................................................................. [1]
(ii) Explain, in terms of energy transfer, why it is likely that the eastern green mamba feeds on other organisms in addition to yellow winged bats. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. [3]
(iii) Suggest how the information in Fig. 5.3 can be used in the control of malaria in other areas of Kenya. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. [2]
(e) Both male and female adult A. gambiae feed on sweet potato plants. Fig. 5.4 shows a sweet potato plant.
Suggest the parts of the sweet potato plants that are the main source of food for adult A. gambiae and explain your answer. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. ............................................................................................................................................................................................. [2]

(a) The thickness of the different chambers of the mammalian heart is due to the amount of cardiac muscle present. The atria have less cardiac muscle than the ventricles, and hence thinner walls.

In terms of their functions, explain why the atria have thinner walls than the ventricles.
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(b) Name the dividing wall separating the right and left sides of the mammalian heart.
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(c) Transpiration and translocation are both processes occurring in plants.

(i) State one way in which transpiration differs from translocation.
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(ii) State one way in which transpiration and translocation are similar.
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