9700_w19_qp_22
A paper of Biology, 9700
Questions:
6
Year:
2019
Paper:
2
Variant:
2
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1
is a photomicrograph of a transverse section through the stem of creeping buttercup, Ranunculus repens. Draw one label line on to indicate one precise location where phloem sieve tubes occur. State the role of phloem sieve tubes. A good quality plan diagram of will show only the tissues in the stem in their correct location and in the correct proportions. State the name of the tissue that forms the outer layer of the stem section of R. repens in . State the piece of equipment that can be used in the light microscope to work out the correct proportions of the tissues. Draw a diagram in the space provided to show the structure of a typical plant cell. Label your diagram with the name of any structures that are found only in plant cells. Do not label any structures that are also found in animal cells.
7. Transport in plants  →  7.1. Structure of transport tissues
1. Cell structure  →  1.2. Cells as the basic units of living organisms
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2
People who smoke tobacco are at an increased risk of developing non-infectious diseases of the gas exchange system and the cardiovascular system. In 2004, a study was carried out on the most popular brands of filter cigarettes from each of the six World Health Organization (WHO) regions. In this study, the smoke passing through the filter was analysed for the tar, nicotine and carbon monoxide (CO) content for each brand of cigarette. For each WHO region, the mean content of tar, nicotine and carbon monoxide of the different brands of cigarette was calculated. The results are shown in . Key to WHO regions AFRO = African Region AMRO = Region of the Americas EMRO = Eastern Mediterranean Region EURO = European Region SEARO = South-East Asia Region WRPO = Western Pacific Region AFRO AMRO EMRO WHO Region EURO SEARO WRPO mg per cigarette Tar Nicotine (×10) CO With reference to , list the two WHO regions where smokers are at the highest risk of developing diseases of the gas exchange or cardiovascular systems. With reference to , explain why smoking a popular brand of cigarette from the AFRO region is more likely to increase the risk of blood clots forming than smoking a popular brand of cigarette from the EURO region. One short-term effect of cigarette smoking is a decrease in the supply of oxygen to body tissues. Describe and explain why cigarette smoking leads to a decrease in the supply of oxygen to body tissues.
9. Gas exchange  →  9.1. The gas exchange system
8. Transport in mammals  →  8.2. Transport of oxygen and carbon dioxide
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3
A red blood cell goes through a number of stages in the bone marrow before it is released into the circulation to carry out its role of oxygen transport. is a transmission electron micrograph of developing red blood cells in the bone marrow. Each cell is known as an erythroblast. shows erythroblasts at a higher magnification than can be obtained using the light microscope. Explain the advantages of using an electron microscope to obtain images such as that in . Describe the differences between an erythroblast and a mature red blood cell. The maturing red blood cell synthesises haemoglobin and other proteins. Complete Table 3.1 to: • name three organelles (cell structures) that are involved in the synthesis of a fully functioning protein • state one way in which the named organelle is involved in protein synthesis. Table 3.1 organelle how the organelle is involved in protein synthesis shows a reversible reaction that takes place within red blood cells. CO2 + H2O H2CO3 Name the protein that catalyses the reaction shown in . The SPTB gene codes for a protein that provides stability and support to the cell surface membrane of the red blood cell. Mutations in SPTB result in red blood cells that are spherical in shape. This mutation leads to a disease known as spherocytosis type 2. Suggest why a person with spherocytosis type 2 has a reduced ability to take up oxygen in the pulmonary capillaries compared with a person who has normal red blood cells. Increases in the water potential of the blood plasma have greater effects on red blood cells in people with spherocytosis type 2 than on normal red blood cells. Compare and explain the effects of an increase in the water potential of blood plasma on spherocytosis type 2 red blood cells and normal red blood cells.
8. Transport in mammals  →  8.1. The circulatory system
8. Transport in mammals  →  8.2. Transport of oxygen and carbon dioxide
2. Biological molecules  →  2.3. Proteins
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4
Carbohydrates, proteins and nucleic acids are types of biological molecule. Within each type, there are examples of molecules that can be described as polymers. A polymer is a large molecule composed of smaller repeating molecules known as monomers. Complete Table 4.1 to produce a summary of some named biological polymers. Table 4.1 polymer constituent monomer type of bond between monomers amylose glucose cellulose glucose collagen peptide DNA DNA nucleotide glycogen glycosidic Explain why an amylose molecule and a cellulose molecule have very different structures, even though they both have glucose as the constituent monomer. Polymerisation of DNA nucleotides occurs during the semi-conservative replication of a molecule of DNA during interphase. Describe the semi-conservative replication of DNA.
6. Nucleic acids and protein synthesis  →  6.1. Structure of nucleic acids and replication of DNA
2. Biological molecules  →  2.2. Carbohydrates and lipids
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5
Countries that have a high number of cases of malaria also have problems with diseases caused by bacteria. This means that many people in these countries are prescribed antibiotics, such as penicillin, for the treatment of bacterial infections. Outline how penicillin acts on bacterial cells. The female Anopheles mosquito is the vector of the Plasmodium pathogen that causes malaria. The insect takes in Plasmodium when feeding on blood from an infected person. At a later stage the insect can transmit the pathogen when taking a blood meal from an uninfected person. Name one of the four species of Plasmodium that can cause malaria. The male Anopheles mosquito does not feed on blood and so does not act as a vector. Suggest why there is a difference in this feeding behaviour between male and female Anopheles. Research has shown that Plasmodium is not always transmitted to uninfected people. Two main reasons for this have been suggested. • The immune system of mosquitoes kills Plasmodium while it is still in the gut. • Bacteria living in the gut of mosquitoes compete with Plasmodium so it does not survive to continue its life cycle. A study was carried out to see if taking antibiotics affects the risk of transmission of malaria. Some observations and results of the study are summarised in . individuals with malaria are taking antibiotics Anopheles mosquitoes take blood meals higher survival rate of Plasmodium in gut of Anopheles individuals with malaria are not taking antibiotics Anopheles mosquitoes take blood meals lower survival rate of Plasmodium in gut of Anopheles Suggest explanations for the results shown in and comment on the importance of these results for doctors working in countries that have malaria and a high number of bacterial infections. After many years of intense research and development, WHO reported in 2016 that a pilot vaccination programme would be trialled between 2017 and 2020. The programme uses a vaccine acting against the most widespread species of Plasmodium. Explain the difficulties faced by researchers in developing a malaria vaccine.
10. Infectious diseases  →  10.1. Infectious diseases
10. Infectious diseases  →  10.2. Antibiotics
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6
Telomerase is an enzyme that is important in maintaining the telomeres that are located at the ends of chromosomes. Explain the importance of telomeres. Suggest why telomerase is present in much higher quantities in stem cells and cancer cells than in other cell types. Studies suggest that telomerase is a flexible molecule when binding its substrate. The active site changes its shape slightly to allow the formation of the enzyme-substrate complex. Name the theory that describes this mode of enzyme action. An investigation was carried out into the effect of substrate concentration on the activity of telomerase. The results are shown in . 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 rate of reaction / arbitrary units substrate concentration / μmol dm–3 With reference to , explain the difference in the rates of reaction obtained for telomerase at a substrate concentration of 0.2 μmol dm−3 compared with a substrate concentration of 1.6 μmol dm−3.
3. Enzymes  →  3.1. Mode of action of enzymes
3. Enzymes  →  3.2. Factors that affect enzyme action
5. The mitotic cell cycle  →  5.1. Replication and division of nuclei and cells
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