AS & A Level Biology - 9700 Paper 2 2011 Winter Zone 1

Fig. 1.1 is a diagram of a cell surface membrane.

(a) Use a label line and the appropriate letter to label each of the following on Fig. 1.1.
P protein for active uptake of potassium ions
Q protein for facilitated diffusion of polar molecules
R receptor site for a hormone
S hydrophilic heads of phospholipids on the internal surface of the membrane
T molecule that modifies the fluidity of the membrane [5]
(b) Some cells take in bacteria by endocytosis.
Explain how endocytosis occurs at a cell surface membrane.
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A student investigated the initial rate of reaction of catalase in breaking down hydrogen peroxide into oxygen and water:

catalase
$$2H_2O_2 \rightarrow O_2 + 2H_2O$$

The volume of oxygen collected was recorded over a period of 140 seconds. The results are shown in Fig. 2.1.



Fig. 2.1

(a) (i) Use the information in Fig. 2.1 to calculate the initial rate of reaction in cm³ s⁻¹.
Show your working.
answer ............................................. cm³ s⁻¹ [2]

(ii) Explain the change in volume of oxygen collected as shown in Fig. 2.1.
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The student continued the investigation by determining the initial rates of reaction for five different concentrations of hydrogen peroxide. The line marked W in Fig. 2.2 shows the results.

The whole procedure was repeated after adding copper ions to the different concentrations of hydrogen peroxide. The line marked V on Fig. 2.2 shows the results.



Fig. 2.2

(b) Use the information in Fig. 2.2 to explain the effect of copper ions on the action of an enzyme, such as catalase.
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(c) Enzyme molecules in cells eventually stop working and are broken down.
Outline how cells replace the enzymes that are broken down.
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(a) Explain how a molecule of haemoglobin shows the four levels of organisation of protein molecules.

primary structure ...............................................................................................................
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secondary structure .................................................................................................
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tertiary structure .......................................................................................................
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quaternary structure ...............................................................................................
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(b) Use the genetic dictionary to describe the similarities and differences between the two variants of haemoglobin.



There are many different variants of haemoglobin. The sequence of bases in DNA that code for the first seven amino acids in two variants of the $\beta$-globin polypeptide are shown in Fig. 3.2.

The genetic dictionary for some of the amino acids is in Table 3.1.





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(c) Collagen is a fibrous protein found in many tissues in animals.

(i) State the function of collagen in the walls of arteries.

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(ii) State one way in which the structure of collagen differs from the structure of haemoglobin.

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(a) (i) Name two factors that increase the chances that cancer will develop.
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(ii) State why lung cancer is categorised as a non-infectious disease.
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The effectiveness of anti-cancer drugs may be determined by growing different tumours in culture. The effectiveness of two drugs on two human tumours (A and B) from different tissues was assessed. The two drugs, T138067 and vinblastine, were added to the tumours in culture on days 5, 12, and 19. The volumes of the tumours were compared with the volumes of tumours that were not treated with any drugs. The results are shown in Fig. 4.1.


(b) Use the data in Fig. 4.1 to compare the effectiveness of the two drugs used to treat the tumours.
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(c) Vinblastine disrupts the formation of the spindle apparatus during mitosis. Explain how vinblastine has its effect as an anti-cancer drug.
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Phloem transfer cells are modified companion cells that move sucrose and other assimilates from mesophyll tissue into phloem sieve tube elements.
Fig. 5.1 is an electron micrograph of a phloem transfer cell.

magnification = × 10 000
Fig. 5.1
(a) Calculate the actual distance across the transfer cell from X to Y.
Show your working and express your answer to the nearest micrometre.
answer ......................................... μm [2]
(b) With reference to Fig. 5.1, explain how phloem transfer cells help in the movement of sucrose from the mesophyll of a leaf into a phloem sieve tube element.
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(c) Explain how sucrose in the phloem sap is moved from sieve tube elements in leaves to cells in a sink, such as a root.
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Phagocytes and lymphocytes are part of the body’s cellular response to infection by pathogens.

Fig. 6.1 shows the origin and maturation of phagocytes and lymphocytes.



Fig. 6.1

(a) Name the site of origin of phagocytes and lymphocytes. [1]

(b) Name:

(i) cells A, B and C

A .......................................................................................................

B .......................................................................................................

C ....................................................................................................... [3]

(ii) organ D. [1]

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(c) Explain the roles of the cells, A, B and C in an immune response.

In your answer use the terms antigen and non-self.

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