11. Immunity
A section of Biology, 9700
Listing 10 of 303 questions
When preparing infertile women for in-vitro fertilisation (IVF), it is necessary to stimulate the growth and maturation of several ovarian follicles. This is done by giving daily injections of the glycoprotein hormone, follicle stimulating hormone (FSH). Each molecule of FSH has quaternary structure and consists of two different polypeptide chains, α and β. Explain what is meant by quaternary structure. Human FSH can be extracted from women’s urine (u-hFSH). A procedure involving the use of monoclonal antibodies is used to produce purified u-hFSH. Suggest how monoclonal antibodies can be used to obtain purified u-hFSH from urine. Recombinant human FSH (r-hFSH) can be produced by adding the genes coding for the α and β polypeptide chains of FSH to mammalian ovary cells. Suggest why mammalian cells are needed to produce r-hFSH, rather than bacterial cells. In IVF treatment, a second hormone, human chorionic gonadotrophin (hCG) is injected when mature ovarian follicles (Graafian follicles) have developed. Draw a labelled diagram to show the structure of a mature ovarian follicle. The effectiveness of r-hFSH was compared with that of u-hFSH. Women starting IVF treatment were randomly divided into two groups and given either r-hFSH or u-hFSH. The differences between the two groups of women after FSH treatment are shown in Table 2.1. Table 2.1 women receiving r-hFSH women receiving u-hFSH number of women mean number of mature follicles per woman concentration of oestrogen in the blood / nmol dm−3 6.55 3.95 With reference to Table 2.1, compare the effects of treatment with r-hFSH and u-hFSH and suggest explanations for the differences. The probability of the results for the mean number of mature follicles per woman occurring by chance is  0.002. Explain what is meant by this probability.
9700_s15_qp_43
THEORY
2015
Paper 4, Variant 3
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Globally, measles is an important disease that mainly affects children. Many deaths from measles occur in children under five years of age. Table 3.1 shows the population of six countries in Africa in 2009 and the number of cases of measles per 100 000 people for the four years 2009 to 2012. All six countries are classified as low-income countries. Table 3.1 country population in number of cases per 100 000 people Central African Republic 4 266 000 0.26 0.05 15.31 3.12 Chad 11 371 000 1.45 1.66 71.60 0.96 Eritrea 5 558 000 1.48 0.89 0.81 3.16 Ethiopia 84 838 000 1.39 4.86 3.64 4.74 Gambia 1 628 000 0.00 0.12 0.00 0.00 Niger 15 303 000 5.23 2.34 4.67 1.59 The actual number of cases of measles in Chad in 2009 was 165 and in Eritrea was 82. Calculate the actual number of cases of measles in Ethiopia in 2009. Show your working. Use the data for Chad, Eritrea and Ethopia to explain the advantages of showing the data in Table 3.1 as number of cases of measles per 100 000 people rather than the actual number of cases. Vaccination is known to protect populations against infectious diseases. Some of the data in Table 3.1 (on page 4) and (on page 6) support this statement. Describe the data that support this statement and comment on the data that do not support this statement. The successful eradication of smallpox involved an intensive global vaccination programme. It is hoped that the same can be achieved with measles. Outline two features, apart from cost, of the smallpox eradication programme that may have made it easier to eradicate than measles. State precisely the type of immunity gained by receiving a measles vaccine. Planning the prevention and control of measles using a vaccination programme means that financial costs must be considered. State two examples of these costs.
9700_s16_qp_22
THEORY
2016
Paper 2, Variant 2
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Much success was made in reducing the number of cases of malaria between 2000 and 2015. Explain how malaria is transmitted. Diagnostic test strips for malaria contain monoclonal antibodies. The test strips detect antigens produced by the pathogens that cause malaria. shows stages in the production of monoclonal antibodies. The information in three of these stages is incomplete. Complete . malarial antigen injected into mouse immune response occurs in mouse plasma cells extracted from spleen of mouse plasma cells with myeloma cells formation of cells myeloma cells specific divide to form many plasma cells shows two diagnostic test strips for malaria. MALARIA C T S A negative result MALARIA C T S A positive result • A sample of blood from a person suspected of having malaria is put into the well labelled S. • A buffer solution is put into the well labelled A. • The buffer solution moves the blood towards the results window. • A line at position C indicates that the test is working correctly. • A line at position T indicates a positive result for malaria. State three advantages of using test strips for malaria, such as those shown in . The highest number of cases of malaria occur in sub-Saharan Africa and South-East Asia. Discuss the factors that determine the global distribution of malaria.
9700_s21_qp_21
THEORY
2021
Paper 2, Variant 1
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Outline the hybridoma method for the production of a monoclonal antibody. Herceptin is a monoclonal antibody used in the treatment of some breast cancers. It binds strongly to molecules of a receptor protein, HER2, that is produced in abnormally large quantities in the plasma (cell surface) membranes of about 30% of human breast cancers. Investigations have been made into the most effective way to use Herceptin to treat breast cancer. One experiment investigated the ability of different treatments to induce cell death in breast cancer cells. Herceptin and X-ray treatment were used both separately and together. The results are shown in . 1.0 2.0 ability to induce cell death / arbitrary units no treatment Herceptin only X-ray treatment only Herceptin and X-ray treatment With reference to , compare the effects on breast cancer cells of the different treatments calculate the percentage increase in the ability to induce cell death of using Herceptin and X-ray treatment compared with using Herceptin only. Show your working. A second experiment investigated the effect of increasing doses of X-rays on the survival of breast cancer cells in the presence and absence of Herceptin. The results are shown in . 1.0 10.0 mean percentage of cells surviving (log scale) absorbed dose of X-rays / J kg–1 X-rays and Herceptin X-rays With reference to , compare the effects of increasing doses of X-rays on cells in the presence and absence of Herceptin suggest an explanation for the effect of Herceptin.
9700_w08_qp_4
THEORY
2008
Paper 4, Variant 0
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Questions Discovered
303