9700_w13_qp_22
A paper of Biology, 9700
Questions:
6
Year:
2013
Paper:
2
Variant:
2
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1
is a diagram of a transverse section through a vein. Y X magnification × 35 Calculate the actual diameter of the vein marked by the line X–Y. Show your working and give your answer in millimetres . answer mm The presence of a valve would help to confirm that the blood vessel in is a vein and not an artery. Describe three structural features of the blood vessel shown in that would help to identify it as a vein and not as an artery. 1. 2. 3. For Examiner’s Use Explain how the following structural features of a capillary are related to its function. The capillary wall is composed of a single layer of squamous epithelial cells. The diameter of the capillary lumen is approximately 8 μm. The inner lining of arteries and veins is composed of a layer of epithelial cells supported by a layer of elastic and connective tissue. The epithelial cells are capable of cell division by mitosis. State the role of mitosis in cell division of epithelial cells. Explain why the epithelial cells undergo mitosis and not meiosis. For Examiner’s Use is a diagram of a cell in late prophase of mitosis. Complete to show the same cell in the anaphase stage of mitosis.
8. Transport in mammals  →  8.1. The circulatory system
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2
For Examiner’s Use Keratin and chitin are two important biological molecules. Keratin is found in hair, fur and skin. Chitin is a modified polysaccharide found in a number of different organisms, for example in fungal cell walls and the hard outer skeletons of insects. Features of chitin and keratin are shown in the boxes in . example: Keratin and chitin are insoluble in water cellulose triglyceride amylopectin collagen Keratin and chitin have structural functions Keratin is a fibrous protein The monomers of chitin are β-1,4 linked Keratin and chitin contain nitrogen Write, in each box, the biological molecules from the list below that have the same feature. Each box may contain one, or more than one, biological molecule. The first box has been completed as an example. amylopectin cellulose collagen haemoglobin mRNA triglyceride For Examiner’s Use Chitin and the products of chitin hydrolysis have many useful medical and environmental applications. Chitinase enzymes can be used commercially to hydrolyse chitin. Enzyme stability and activity are important considerations in technological applications of chitinase. is a graph showing the effects of temperature on chitinase extracted from a soil bacterium. The relative activity of the enzyme was measured at different temperatures, with 100% representing maximum enzyme activity. relative activity / % temperature / °C With reference to , state the optimum temperature for the chitinase enzyme. For Examiner’s Use is a graph showing how temperature affects the stability of chitinase. The activity of the enzyme was measured over a time period of 72 hours at each of five different temperatures. relative activity / % time / h 28 °C 37 °C 40 °C 50 °C 60 °C With reference to and , describe and discuss the effect of temperature on chitinase activity and stability.
2. Biological molecules  →  2.2. Carbohydrates and lipids
3. Enzymes  →  3.2. Factors that affect enzyme action
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3
For Examiner’s Use Explain the need for transport systems in plants. is a drawing of a transverse section through part of the stem of a dicotyledonous plant. Cell A and cell B are involved in the transport of dissolved organic molecules. cell A cell B 1 +m Name cell A and cell B. cell A cell B For Examiner’s Use With reference to , explain how the different structures of cell types A and B are related to their function. Complete Table 3.1 to state four differences between transport systems in mammals and in plants. Table 3.1 transport system in mammals transport system in plants
7. Transport in plants  →  7.1. Structure of transport tissues
7. Transport in plants  →  7.2. Transport mechanisms
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4
For Examiner’s Use Staphylococcus aureus is a bacterium that is the cause of many different infectious diseases. is a diagram of S. aureus. 1 +m Cell structures, such as mitochondria, endoplasmic reticula (ER), Golgi apparatus, lysosomes and chloroplasts are found only in eukaryotic cells. These are not present in . With reference to , describe other features that support the fact that S. aureus is a prokaryote. State the main difference in the composition of the plant cell wall compared to the bacterial cell wall. plant cell wall bacterial cell wall For Examiner’s Use Bacterial cells behave in a similar way to plant cells when immersed in solutions of different water potential. Suggest and explain what would happen to bacteria placed in a solution with a water potential more negative than their cell contents. Some strains of S. aureus have become resistant to one or more of the antibiotics used to treat infections. The mechanisms of antibiotic resistance involve proteins, for example: • enzymes to breakdown antibiotics • membrane proteins that inactivate antibiotics • membrane proteins that pump out antibiotics. Explain why antibiotic resistance arises as a result of mutation.
10. Infectious diseases  →  10.2. Antibiotics
4. Cell membranes and transport  →  4.2. Movement into and out of cells
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5
For Examiner’s Use Read the following passage. The three-toed sloth, Bradypus variegatus, is a very slow-moving mammal found in Central and South America that spends most of its life living in trees. The thick, long grey fur of the sloth in has a green appearance. Individual hairs of the sloth have grooves in them where water can collect. Research has shown that the green colour is due to the presence of algae living on the sloth’s fur, the most common species being Trichophilus welckeri. Algae are eukaryotic, photosynthetic organisms. Many other species of non-photosynthetic eukaryotes, both unicellular and multicellular, have been found living on the sloth’s fur. These include different species of roundworms, insects and saprotrophic fungi. For Examiner’s Use Explain the ecological terms population and community, using examples given in the passage. population community Suggest why the sloth and its fur can be described as a small ecosystem.
18. Classification, biodiversity and conservation  →  18.2. Biodiversity
18. Classification, biodiversity and conservation  →  18.1. Classification
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6
For Examiner’s Use Nicotine, in cigarette smoke, is highly addictive. A nicotine vaccine has been developed to try and reduce the effects of addiction. The vaccine stimulates an immune response to produce antibodies that bind to the nicotine molecule. is a diagram of an antibody molecule. On : • label three structural features that enable an antibody molecule to carry out its function. • next to each label, state the function of the feature. Nicotine has an effect on the cardiovascular system, such as making platelets sticky, so causing blood to clot. This increases the risk of thrombosis and reduces blood flow. Outline other effects of nicotine on the cardiovascular system.
11. Immunity  →  11.2. Antibodies and vaccination
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