AS & A Level Biology - 9700 Paper 2 2021 Summer Zone 1

(a) Calculate the actual width of the cell labelled X.
Write down the formula you will use to make your calculation.
Show your working and give your answer in micrometres to one decimal place.

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(b) (i) Table 1.1 lists some biological molecules found in plant cells.
Complete Table 1.1 by choosing one letter from Fig. 1.1 that indicates a cell structure where each biological molecule is found.

\[ \text{Table 1.1} \]
\[ \begin{array}{|c|c|} \hline \text{biological molecule} & \text{letter from Fig. 1.1} \\ \hline \text{DNA} & \\ \hline \text{cellulose} & \\ \hline \text{phospholipid} & \\ \hline \text{histone proteins} & \\ \hline \end{array} \]

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(ii) State the name of a cell structure, visible in Fig. 1.1, where ATP is synthesised.
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(iii) Name a cell structure that produces mRNA.
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(c) Describe the evidence from Fig. 1.1 that shows that the image is a transmission electron micrograph.
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Fig. 2.1 shows three molecules of water.

Fig. 2.1
(a) Describe the hydrogen bonding that occurs between the water molecules shown in Fig. 2.1.
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(b) The human enzyme, salivary amylase, is composed of one polypeptide. Fig. 2.2 represents the structure of a molecule of salivary amylase.

Fig. 2.2
(i) Explain the role of hydrogen bonding in maintaining the secondary structure of proteins, such as salivary amylase.
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(ii) Explain the role of hydrogen bonding in maintaining the tertiary structure of proteins such as salivary amylase.
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(c) Outline the importance of water as a solvent in \textit{plants}.
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(a) The Visking tubing used by the student was not permeable to sucrose.
Explain the results shown in Table 3.1.

[Table_1]
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(b) When red blood cells are placed in water they are destroyed by bursting.
The student also investigated how red blood cells are affected by immersion in solutions of sodium chloride of different concentration. Blood samples of the same volume were added to solutions of sodium chloride in separate test-tubes.
After 10 minutes, the student took 0.1 cm³ of the blood samples from the test-tubes and estimated the percentage of red blood cells that had burst in each blood sample.
Fig. 3.2 shows the student's results.

Describe and explain the effects on red blood cells of immersion in different concentrations of sodium chloride as shown in Fig. 3.2.
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(a) The induced-fit hypothesis and the lock-and-key hypothesis are used to describe the mode of action of enzymes.

Explain the induced-fit hypothesis.

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(b) Radish plants contain the enzyme peroxidase that catalyses the breakdown of hydrogen peroxide.

Students investigated the effect of increasing the concentration of hydrogen peroxide on the activity of peroxidase extracted from radish.

The results of their investigation are shown in Fig. 4.1.

[Image_1: Graph showing initial rate of reaction vs concentration of hydrogen peroxide]

(i) Explain the effect of increasing the concentration of hydrogen peroxide on the initial rate of reaction as shown in Fig. 4.1.

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(ii) The students determined the $K_m$ for radish peroxidase as $0.10 \text{ mmol dm}^{-3}$.

With reference to Fig. 4.1, describe how they determined the $K_m$.

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(c) A further investigation found that the $K_m$ for carbonic anhydrase is $12 \text{ mmol dm}^{-3}$.

Describe the role of carbonic anhydrase in the transport of carbon dioxide.

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(a) Explain how malaria is transmitted.
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(b) Diagnostic test strips for malaria contain monoclonal antibodies. The test strips detect antigens produced by the pathogens that cause malaria.

Fig. 5.1 shows stages in the production of monoclonal antibodies. The information in three of these stages is incomplete.

Complete Fig. 5.1.

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(c) Fig. 5.2 shows two diagnostic test strips for malaria.



• A sample of blood from a person suspected of having malaria is put into the well labelled S.
• A buffer solution is put into the well labelled A.
• The buffer solution moves the blood towards the results window.
• A line at position C indicates that the test is working correctly.
• A line at position T indicates a positive result for malaria.

State three advantages of using test strips for malaria, such as those shown in Fig. 5.2.

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(d) The highest number of cases of malaria occur in sub-Saharan Africa and South-East Asia.

Discuss the factors that determine the global distribution of malaria.

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(a) Name the cell structures labelled A and E.

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(b) State the function of the structures labelled F.

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(c) Name the process by which bacteria are taken into the cell at C.

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(d) With reference to the processes occurring at B and at D in Fig. 6.1, outline the role of acid hydrolases in lysosomes.

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(e) Carrier proteins in the membranes of lysosomes maintain a lower pH than the surrounding cytoplasm by moving hydrogen ions.

Suggest how the carrier proteins maintain the lower pH within the lysosomes.

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