AS & A Level Biology - 9700 Paper 2 2017 Summer Zone 2

(a) In multicellular organisms, the structure of different cell types is adapted to their function. Within these cells there are a number of different organelles, each with a particular function. Table 1.1 contains information about the structure and function of five different types of cell. The table also includes, for each type of cell, one example of a cell organelle that is essential for the function to be carried out. Complete Table 1.1.

Table 1.1

[Table_1]

type of cell | function of cell | example of organelle required to carry out function
palisade mesophyll | | chloroplast
Leydig | synthesis of steroid hormones |
| production of secretory vesicles for release of antibody | Golgi body
root hair cell | active uptake of mineral ions from the soil |
pancreas acinar | synthesis of enzymes |

[5]

(b) A tissue is a collection of one or more types of cell, specialised to carry out a particular function. An organ can be considered a structural unit within an organism that:
• consists of more than one type of tissue
• performs a particular function.
The aorta is the main artery of the body. Explain, with reference to its structure and function, whether the aorta may be described as a tissue or an organ.
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Lipase is an enzyme with many commercial uses. Some species of bacteria are of great interest as they produce large quantities of lipase.

(a) Complete Fig. 2.1 to show the hydrolysis of triglyceride by lipase.

triglyceride + .................... lipase → ............................
Fig. 2.1 [2]

Researchers carried out investigations into lipase extracted from a bacterium found in hot springs.

(b) To measure the activity of the bacterial lipase during their investigations, the researchers used a method based on the biological test for triglycerides.

Outline a biological test that could be carried out to show the presence of triglyceride in a liquid mixture and describe the positive result for this test.

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(c) The researchers investigated the effect of pH values between pH 2.0 and pH 10.5 on the activity of bacterial lipase in hydrolysing triglyceride at a temperature of 37°C.

The results are shown in Fig. 2.2. Fig. 2.2

With reference to Fig. 2.2, describe the effect of pH on the activity of bacterial lipase.

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(d) A separate investigation into the effect of pH on the same bacterial lipase compared the enzyme free in solution with the enzyme immobilised by physical attachment to a stable polymer.

At a temperature of 37°C, the optimum pH of the enzyme free in solution was the same as that shown in Fig. 2.2. The optimum pH of the immobilised enzyme was measured as pH 4.

(i) Suggest one reason to explain why the enzyme free in solution has a different optimum pH compared to the immobilised enzyme.

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(ii) Suggest one advantage of immobilising the extracted lipase for commercial use.

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Malaria is a disease caused by the protocist, Plasmodium. The organism has a very complex life cycle as it has two hosts, a human and a mosquito.

(a) Name one of the four species of Plasmodium that infects humans.
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(b) State the name of the mosquito that is host to Plasmodium.
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Fig. 3.1 is a transmission electron micrograph showing the developing Plasmodium cells inside a protective structure known as an oocyst. In this stage of the life cycle the oocysts are found in the mosquito gut. When mature, the Plasmodium cells are released and travel to the salivary glands of the mosquito.



(c) The magnification used in Fig. 3.1 can also be obtained using a light microscope.
Suggest why an electron microscope was used to obtain this image instead of a light microscope.
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(d) Use the scale bar to calculate the magnification of the image shown in Fig. 3.1.
Write down the formula and use it to make your calculation. Show your working.
[Table_1]
magnification × ...............................................................[3]

(e) Outline the role of the mosquito in the transmission of malaria.
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(a) Fig. 4.1 summarises a cell cycle for a meristematic cell in the root tip. The two phases of this cell cycle are shown:
• interphase, which is divided into the $G_1$, S, and $G_2$ stages
• cell division, which is divided into stages 1–5.

(i) In Fig. 4.1, stage 2 is metaphase.
The stages shown in Fig. 4.1 are listed below. Draw a circle around the stage in the cell cycle that is cytokinesis and describe what happens in this stage in the root tip meristematic cell.
1 2 3 4 5 $G_1$ S $G_2$
[3]
(ii) The stages shown in Fig. 4.1 are listed below. Draw a circle around the stage in the cell cycle in which the semi-conservative replication of DNA occurs and state what is meant by semi-conservative replication.
1 2 3 4 5 $G_1$ S $G_2$
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(b) Meristematic cells have a similar role to stem cells found in animals.
Suggest the role of a meristematic cell and explain the features that help it to carry out its role.
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(c) Meristematic regions in the plant can sometimes be described as strong sinks.
(i) State what is meant by a sink.
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(ii) Suggest what is meant by a strong sink.
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(d) Describe and explain how sucrose is loaded into phloem sieve tubes.
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(a) The epithelial lining of the gas exchange system is adapted for defence against pathogens.
(i) List the structures in the gas exchange system that have a ciliated epithelial lining.
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(a) The epithelial lining of the gas exchange system is adapted for defence against pathogens.
(ii) Name the cells in the ciliated epithelium that synthesise and secrete mucus.
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(b) The infectious lung disease, pneumonia, can be caused by \textit{Streptococcus pneumoniae}.
Most healthy people inhaling air containing these bacteria do \textbf{not} become ill because of the action of the alveolar macrophages.
Outline the mode of action of an alveolar macrophage in response to the presence of \textit{S. pneumoniae}.
You may use diagrams with notes to help your answer.
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(c) Suggest how the structure of the alveolar wall changes so that an alveolus bursts.
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(d) Some alveolar cells produce a surfactant that helps to prevent the collapse of alveoli on exhalation. Too much surfactant decreases the efficiency of gas exchange in the alveoli.
A glycoprotein known as GM-CSF is released by some cells of the immune system when there is too much surfactant in the alveoli. Excess surfactant is then broken down by alveolar macrophages.
Receptors for GM-CSF are on the cell surface membranes of alveolar macrophages.
Explain how maintaining the correct quantity of surfactant in the alveoli is the result of a cell signalling mechanism.
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(a) Table 6.1 shows some features of an antibody molecule and a haemoglobin molecule.

Complete Table 6.1 to produce a summary of the features of the two molecules.

Table 6.1