AS & A Level Biology - 9700 Paper 2 2010 Winter Zone 2

(a) The first column in Table 1.1 shows some of the events that occur in the production of a protein in a cell and its eventual release from the cell.

Table 1.1

[Table_1]

(i) In Table 1.1, write the sequence in which the events occur, using 1 as the first process in the sequence. [2]

(ii) From the list A to F below, choose one cell location for each event and write the letter in Table 1.1. Each letter may be used once, more than once, or not at all.

A Golgi apparatus
B lysosome
C nucleus
D rough endoplasmic reticulum
E smooth endoplasmic reticulum
F plasma (cell surface) membrane [3]

(b) Describe the process of exocytosis.
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(c) One example of protein modification is the removal of the first amino acid, methionine, from a newly formed polypeptide chain to make a functioning protein.

(i) The DNA nucleotide sequence that specifies the amino acid methionine is TAC.

State the mRNA nucleotide sequence that is complementary to the DNA sequence for methionine.
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(ii) Suggest two other ways in which the polypeptide chain is modified to produce the functioning protein.
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Malaria is an infectious disease that is considered by the World Health Organization to be a disease of worldwide importance.
(a) Explain what is meant by the term \emph{infectious}.
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(b) Name \emph{one} species of organism that causes malaria.
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(c) Explain the significance of the following statements in the control of malaria.
(i) The female \emph{Anopheles} mosquito has been more closely studied with regard to malaria than the male \emph{Anopheles} mosquito.
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(ii) The infective stages of the malarial organism are present in anti-coagulant produced by the mosquito.
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(iii) After circulating in the blood for a short time, the pathogen enters liver cells of the newly infected person and then enters red blood cells.
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(d) Discuss the factors that determine the distribution of malaria worldwide.
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(a) Enzymes are globular proteins that catalyse metabolic reactions.

Describe the features of globular proteins.
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(b) Enzymes can be used to remove cell walls from plant and fungal cells. The cells are incubated in a solution that contains a mixture of enzymes.

(i) Suggest an explanation for the fact that a different mixture of enzymes is required to remove the walls of plant cells compared to the walls of fungal cells.
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(ii) Explain why, when plant cells are incubated with enzymes to remove their cell walls, it is important to maintain an optimum pH.
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(c) A student carried out an investigation into osmosis using red blood cells.

Red blood cells were placed in sodium chloride (salt) solutions at five different concentrations. For each concentration, a sample was added immediately to a microscope slide and the cells were viewed using a light microscope for a period of time. The observations recorded are shown in Table 3.1.

Table 3.1

| concentration of salt solution / % | observation of red blood cells |
|-----------------------------------|------------------------------------------|
| 0.0 | swell and burst, numbers decrease |
| 0.4 | increase in size |
| 0.9 | remain the same size |
| 1.5 | decrease in size |
| 3.0 | smaller and shrivelled |

Explain, in terms of water potential and osmosis, the results that the student obtained.
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(d) The student also carried out a similar investigation using plant cells with cell walls removed. These cells were suspended in a 12% mannitol solution so that the water potential inside and outside of the cells was equal.

Fig. 3.1 is a photomicrograph of these cells.



The student removed a sample of these cells. The sample was placed into distilled water and was viewed using a light microscope.

Describe what you would expect the student to observe and explain why this would not occur with normal plant cells.
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Fig. 4.1 is an incomplete flow chart showing some of the events of the primary immune response that occur after a person has been given a vaccine.

Fig. 4.1
(a) Choose the correct term from the list below to complete Fig. 4.1.

lymphocytes antigens mitosis vaccine
$T_{h}$-lymphocytes plasma cells macrophages
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(b) Explain why the person is unlikely to become ill if they are infected by the same pathogen some months later.
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(c) Some parents decide that their children should not take part in a vaccination schedule.

Suggest how a country-wide vaccination schedule can give protection against infection to \textit{unvaccinated} children.
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[2]

State the term that applies to each of the descriptions (a) to (e).

(a) Storage polysaccharide in animals made of chains of 1,4 linked \( \alpha \)-glucose with 1,6 linkages forming branches.
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(b) A plant that has adaptations to enable it to live in areas where water is in short supply.
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(c) Any cell containing one complete set of chromosomes.
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(d) The name of the trophic level to which photosynthetic organisms belong.
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(e) A process carried out by bacteria that involves the conversion of atmospheric nitrogen into nitrogenous compounds that can be used directly by plants.
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Fig. 6.1 is a section through lung tissue showing an alveolus and its blood supply.
[Image_1: Fig. 6.1]

(a) (i) Name the type of epithelial cell shown by label lines A and B.
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(ii) Describe how the elastic fibres of the alveoli contribute to the healthy functioning of the lungs.
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(b) The actual diameter of the alveolus along the line X–Y is 220 micrometres ($\mu$m). Calculate the magnification of Fig. 6.1.
Show your working and give your answer to the nearest whole number.

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(c) Outline two features of a gas exchange surface that are shown on Fig. 6.1.
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(d) Fig. 6.2 is a simplified diagram of the circulatory system of a human, showing gas exchange in the lungs and in respiring tissue. The partial pressures of oxygen ($pO_2$) and carbon dioxide ($pCO_2$) at four locations are also shown.
[Image_2: Fig. 6.2]

With reference to Fig. 6.2, explain how the differences in $pO_2$ and $pCO_2$ in the alveolus and in blood enable gas exchange in the lungs and respiring tissue.
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