Cambridge A Level Biology 9700 — 2021 May/June Paper 2 · Variant 2

1 (a) Fig. 1.1 is a photomicrograph of a region of eukaryotic tissue. Some of the cells are in stages of mitosis. E F Fig. 1.1 (i) Identify which stage of mitosis is shown in cell E and in cell F in Fig. 1.1. E .............................................. F .............................................. [2] (ii) Microtubules are present within the cells that are in stages of mitosis, but these are not visible in Fig. 1.1. State the function of microtubules in mitosis. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (iii) State, with a reason, whether Fig. 1.1 shows a region of animal or plant tissue. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (b) Semi‑conservative replication of DNA occurs during interphase, before mitosis begins. Write the correct term in the spaces provided to complete each of statements A to D. A The DNA double helix unwinds and is separated into two template strands when ....................................................................... bonds holding the two strands together are broken. B One of the template strands of DNA is copied in fragments. The enzyme ....................................................................... is required to join the fragments together to form a continuous strand of DNA. C Complementary DNA nucleotides are added to the template strands, catalysed by the enzyme ....................................................................... . D ....................................................................... are regions of repeating nucleotide sequences at the ends of chromosomes that allow the continued replication of DNA, without the loss of genes. [4] [Total: 8]

Mark scheme: 1(a)(i) E = metaphase ; F = anaphase ; I early / mid / late R more than one stage given for either E or F 2 1(a)(ii) any one from (assemble) to form / become part of / AW, spindle fibres / spindle ; attach to, centromere ; A kinetochore for centromere A form (part of) kinetochore A to connect, chromatid / chromosome, to, spindle / spindle fibres I to connect, chromosome / centromere, to centrosome example of allowing movement of, chromosomes / chromatids ; e.g. A to, pull chromosomes / orientate chromosomes, at equator A to pull (sister) chromatids apart (at anaphase) A to move, (sister) chromatids / daughter chromosomes, to poles 1 1(a)(iii) must state ‘plant’ to gain mark I vacuoles / large permanent vacuole / vague ref. to shape any one from cell walls present; uniform / regular, shape of cells ; no, cleavage furrow / pinching in of cytoplasm (in cells at cytokinesis) ; cell plate present (in late telophase / cytokinesis, stages) ; 1 Question Answer Marks 1(b) R any answers where a choice is given A hydrogen ; B (DNA) ligase ; C DNA polymerase ; R RNA polymerase I roman numerals, e.g. DNA polymerase I D telomeres ; 4

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2 Sugars are transported within phloem sieve tubes from a source, such as a mature leaf, to a young leaf, which acts as a sink. The young leaf also needs water and dissolved mineral ions, which arrive at the leaf within xylem vessels. (a) As the young leaf matures, the quantity of sugar taken up by the leaf decreases to zero, but the need for water increases. Suggest and explain why the quantity of sugar taken up by the developing leaf decreases to zero over time, but the need for water increases. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [3] (b) The features listed in Table 2.1 are present in one or more of the three cell types: • companion cell • phloem sieve tube element • xylem vessel element. Complete Table 2.1 using a tick (3) if the feature is present and a cross (7) if the feature is absent. Table 2.1 companion phloem sieve xylem vessel feature cell tube element element cytoplasm cell surface membrane lignified cell wall nucleus [4] [Total: 7]

Mark scheme: 2(a) any three from decrease in sugar 1 idea that changing / transition, from sink to source e.g. leaf becomes the source leaf no longer the sink sugars are (now) being moved away from leaf was a growing area, now translocating (sugars) 2 photosynthesis provides enough sugar / (rate of) photosynthesis increases ; A leaf (now) makes enough sugar I makes own food increase in water to max 2 3 increase in size / more cells / increase in (leaf) surface area, (so proportionate increase in water) ; 4 (more cells that need) water to, maintain turgidity / prevent flaccidity / prevent wilting, (because of transpiration) ; 5 increased transpiration / greater number of stomata ; A increased evaporation (greater internal leaf area) 6 water is, a reactant / needed, for photosynthesis ; (in context of increased photosynthesis, more water needed) 7 AVP ; e.g. maturing leaf growth rate slows / mature leaf no growth (more cells, so more) water needed for, cellular reactions / AW e.g. for hydrolysis of starch (more) water needed for, cell elongation / enlarging vacuoles Question Answer Marks 2(b) one mark each correct row ;;; column mark can be used instead of row mark (if higher mark achieved) feature companion cells phloem sieve tube element xylem vessel element cytoplasm   x cell surface membrane   x lignified cell wall x x  nucleus  x x 4

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3 In mammals, some cell signalling molecules are steroid (lipid) hormones. These hormones are transported in the bloodstream to reach capillary networks. At a capillary network, hormones pass out of the blood into tissue fluid. (a) Fig. 3.1 is a diagram of a capillary network. body cells X tissue fluid blood blood to from vein artery Fig. 3.1 (i) Describe the differences between the blood arriving at the arterial end of the capillary network and the tissue fluid surrounding the body cells. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3] (ii) Not all the tissue fluid passes back into the blood capillaries to enter the bloodstream. Some of the tissue fluid drains into blind‑ended vessels, such as vessel X shown in Fig. 3.1. Name the fluid that is formed in vessel X. ..................................................................................................................................... [1] Hormone S is a steroid hormone involved in cell signalling. Fig. 3.2 shows the sequence of events that occurs when hormone S enters a target cell. hormone-receptor complex R DNA B C G nuclear cell surface envelope membrane KEY: not to scale hormone S cell surface membrane receptors cytoplasmic receptors nuclear receptor messenger RNA molecule polypeptide Fig. 3.2 (b) Explain why hormone S, shown in Fig. 3.2, does not need to pass through a transport protein to enter the cytoplasm of the target cell. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (c) The target cell can respond to other cell signalling molecules in addition to hormone S. The cell has receptors in the cell surface membrane, in the cytoplasm and in the nucleus. Explain why hormone S binds only with receptor R in the cytoplasm and not with the other receptors shown in Fig. 3.2. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] (d) The hormone‑receptor complex shown in Fig. 3.2 enters the nucleus and binds to DNA. This switches on a gene coding for a polypeptide that is synthesised in the cytoplasm. (i) Name the structure through which the hormone‑receptor complex enters the nucleus. ..................................................................................................................................... [1] (ii) Name the processes occurring at B and C. B ........................................................................................................................................ C .................................................................................................................................. [2] (iii) Name structure G. ..................................................................................................................................... [1] (e) Cell signalling by hormone S results in the production of a functioning globular protein molecule composed of three identical polypeptide chains. After the synthesis of these polypeptides, changes need to occur to form the functioning globular protein molecule. Outline the changes that need to occur to form the functioning globular protein molecule. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [4] [Total: 15]

Mark scheme: 3(a)(i) accept from either column for mark and assume blood if not stated any three from blood tissue fluid has red blood cells has no red blood cells ; more, white blood cells / leucocytes / named e.g. neutrophils, lymphocytes, monocytes or fewer macrophages fewer white blood cells / leucocytes / named e.g. neutrophils, lymphocytes, monocytes or more macrophages ; has platelets has no platelets ; has, more protein / large proteins or has, plasma proteins / named example e.g albumin / fibrinogen / globulin these are large proteins has, fewer / no large, proteins or has no, plasma proteins / named example e.g. albumin / fibrinogen / globulin only allow fewer plasma proteins if clear the proteins present are small enough to leave blood ; higher, concentration / AW, oxygen A more oxygenated lower, concentration / AW, oxygen A less oxygenated ; higher, concentration / AW, glucose / amino acids / fatty acids lower, concentration / AW, glucose / amino acids / fatty acids ; lower, concentration / AW, carbon dioxide A urea, in liver / muscles I waste higher, concentration / AW, carbon dioxide A urea, in liver / muscles I waste ; higher pressure lower pressure ; 3 3(a)(ii) lymph ; A lymphatic fluid 1 Question Answer Marks 3(b) any two from: 1 can cross / AW, hydrophobic core (of bilayer) / phospholipid bilayer or can pass through gaps between, fatty acid tails / phospholipids ; 2 is, hydrophobic / lipid-soluble / non-polar / not ionic / not charged or not, hydrophilic / water-soluble / polar / ionic / charged ; 3 small size ; 2 3(c) Reject if hormone S or receptor R described as an antigen or enzyme complementary (shape) to / only fits into / specificity for (binding to), R / receptor ; 1 3(d)(i) nuclear pore ; A nuclear pores 1 3(d)(ii) B = transcription ; C = translation ; 2 3(d)(iii) (80S) ribosome ; I 70S 1 Question Answer Marks 3(e) any four from 1 (formation of), secondary / 2° / second level, structure with, alpha-helix / α-helix / beta-pleated sheet(s) / β-pleated sheet(s) ; A β-conformation for β-pleated sheet I incorrect detail of bonds 2 folding / coiling, to form tertiary / 3° / third level, structure ; A ref. to 3D structure as alternative to, folding / coiling A secondary structure, folds / coils, to form tertiary structure R alpha helix / beta-pleated sheet, coils / folds 3 two of hydrogen bonds / ionic or electrostatic bonds / disulfide bonds or bridges / hydrophobic interactions ; I peptide bonds as part of a list that contains two correct bond types these must be in context of tertiary structure 4 (formation of), quaternary / 4° / fourth level structure ; A description e.g. polypeptides held together by, interactions / hydrogen bonds / ionic bonds / disulfide bonds R if peptide bonds included 5 (globular protein) has hydrophilic, amino acids / R-groups / side chains, to, outside / AW ; ora hydrophobic, amino acids / R-groups / side chains, towards centre / AW 6 example of other post-translational modification ; e.g. removal, methionine / met addition sugar group / glycosylation addition phosphate group / phosphorylation addition prosthetic group 4

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4 A person who is exposed to tobacco smoke is at greater risk of lung cancer and chronic obstructive pulmonary disease (COPD). Many people with COPD have both chronic bronchitis and emphysema. These diseases cause changes in the gas exchange system. For example, changes occur in the total lung surface area to volume ratio (SA:V). (a) Tar in tobacco smoke has a number of effects on the cells lining the gas exchange system. State the main effects of tar on the cells lining the gas exchange system that are related to lung cancer and to chronic bronchitis. lung cancer ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... chronic bronchitis ...................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [3] (b) A student investigated the effect of SA:V on diffusion. Agar was prepared with Universal Indicator solution and sodium hydroxide solution. The agar was coloured blue. Three cubes, A, B, and C, were cut from a solid block of blue agar. Each cube was a different size. Universal Indicator solution changes to a red colour in the presence of acid. The student prepared Table 4.1 to show the sizes and SA:V of each cube. Table 4.1 cube length of each total surface volume / SA:V side / cm area / cm2 ..................... A 1 6 1 6:1 B 2 24 8 3:1 C 3 2:1 Complete Table 4.1 by: • writing the correct units for volume • calculating the total surface area, and volume, of cube C. [2] (c) Cubes A, B and C were placed in a small beaker. At time 0 seconds, dilute hydrochloric acid was added to the beaker to cover the cubes. The student timed how long it took for each cube to change colour completely. Complete Fig. 4.1 to show the results that were obtained. shortest time to longest time to change colour change colour completely completely cube ......................... cube ......................... cube ......................... [1] Fig. 4.1 (d) Some people with emphysema may be offered lung volume reduction surgery (LVRS), in which diseased lung tissue is surgically removed. One expected outcome of the surgery is an improvement in total lung surface area to volume ratio (total lung SA:V). Suggest why there is an improvement in total lung SA:V after the surgery has been carried out. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (e) In humans, blood that becomes oxygenated in the lungs reaches body tissues without coming into contact with blood that is deoxygenated. Explain how the blood that becomes oxygenated in the lungs is kept separate from blood that is deoxygenated. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] [Total: 10]

Mark scheme: 4(a) any three from lung cancer to max 2 (tar) is a carcinogen ; acts as mutagen / causes mutations / described ; I mutant cells e.g. causes changes to sequence of, bases / nucleotides, in DNA detail ; I uncontrolled mitosis e.g. tumour suppressor genes switched off protooncogenes to oncogenes / oncogenes switched on (cell cycle) checkpoints fail to function AW cell moves from, G0 / inactive state of cell cycle, to G1 phase (for mitosis) no programmed death / AW chronic bronchitis to max 2 (tar) paralyses / destroys / damages / AW, cilia ; I weakens cilia A damage to ciliated (epithelial) cells consequence to cilia action ; must be related to mp1 e.g. cilia do not, waft away / AW, mucus loss of synchronous rhythm of cilia (tar causes), goblet cells / mucous glands, to, increase in size / enlarge / AW ; A (tar / accumulation of mucus, causes) inflammation more / excess, mucus produced (by, goblet / mucous gland cells) ; I mucus accumulates 4(b) correct units for volume cm3 ; SA and volume calculation (SA) = 54 (V) = 27 ; 2 4(c) A  B  C ; A 6:1  3:1  2:1 A 1  2 3 1 Question Answer Marks 4(d) any two from (in emphysema) alveolar walls break down / alveoli burst, to, produce one large air sac / give a lower SA:V or diseased, tissue / areas / alveoli, has lower SA:V (than healthy tissue) ; removed tissue has (higher proportion of), large air sacs / diseased alveoli ; remaining tissue has, healthy / undamaged / functional / only, alveoli ; AW A volume reduced and functional surface area of lung remains the same A remaining tissue has higher functional surface area (than before surgery) 2 4(e) any two from 1 only oxygenated blood passes through left side of heart ora or oxygenated blood in left side and deoxygenated blood in right side of heart ; 2 septum in heart separates (oxygenated and deoxygenated) blood ; 3 oxygenated blood is in pulmonary, venules / veins and deoxygenated blood is in, pulmonary arteries / arterioles ; 4 (because mixing prevented by) double circulation / double circulatory system / pulmonary and systemic circulations ; 2

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5 Fig. 5.1 is a transmission electron micrograph showing parts of two plant cells. The function of the middle lamella is cell‑to‑cell adhesion. The middle lamella is composed of a polysaccharide known as pectin. Pectin interacts with the polysaccharides cellulose and hemicellulose in the cell walls of the plant cells so that the cell walls are held close together, as shown in Fig. 5.1. Golgi body middle lamella X Fig. 5.1 (a) Cell structure X in Fig. 5.1 is a cytoplasmic channel with strands of cytoplasm passing through the cell walls of the two cells. Name cell structure X and state one function of this cell structure. name ......................................................................................................................................... function ..................................................................................................................................... ............................................................................................................................................. [2] (b) Researchers have discovered that pectin is synthesised within the Golgi body. Golgi vesicles containing pectin are moved to the cell surface membrane for release. (i) Suggest why researchers would not have investigated ribosomes as being the possible location for the synthesis of pectin. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Name the mechanism that is used to transport pectin out of the cell. ..................................................................................................................................... [1] Juices that are extracted commercially from fruits can be made less cloudy by the breakdown of the cell wall using the enzymes cellulase, pectinase and xylanase: • cellulase hydrolyses cellulose • pectinase hydrolyses pectin • xylanase hydrolyses hemicellulose. (c) Fig. 5.2 is a graph showing the effect of cellulose concentration on the activity of cellulase, which is used in making fruit juice less cloudy. 300 240 rate of reaction 180 / mg product cm–3 min–1 120 60 0 0 20 40 60 80 100 cellulose concentration / mg cm–3 Fig. 5.2 Describe and explain the curve shown in Fig. 5.2. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [3] (d) Ultrasound is one possible method that can be used to destroy microorganisms that contaminate fruit juices. Ultrasound is the term given to sound waves that are out of the range of human hearing. An investigation was carried out into the effect of ultrasound on the activity of cellulase, pectinase and xylanase used in fruit juice manufacture. For each enzyme, the effect of ultrasound was compared with no ultrasound on the: • maximum rate of reaction (Vmax) • Michaelis‑Menten constant (Km) • catalytic efficiency (Vmax / Km) Table 5.1 summarises the results. A higher Vmax / Km indicates a higher catalytic efficiency. Table 5.1 comparison comparison Vmax / Km enzyme method of Vmax of Km / min–1 ultrasound higher higher 34 cellulase no ultrasound lower lower 29 ultrasound same lower 945 pectinase no ultrasound same higher 759 ultrasound higher same 146 xylanase no ultrasound lower same 125 (i) In terms of changes in the interaction between enzyme and substrate when ultrasound is used, suggest explanations for the lower Km for pectinase and the higher Vmax for xylanase, as shown in Table 5.1. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [3] (ii) Explain whether the data shown in Table 5.1 supports the recommendation that ultrasound can be used in the manufacture of fruit juices. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 5(a) plasmodesma ; plus any one from R if stated as apoplast 1 allows / AW, symplast, pathway / movement ; 2 allows transport of / AW, water / sucrose / sugars / amino acids / organic substances / ions / mineral salts (A minerals) / lipids / assimilates / hormones / cell signalling molecules ; in context of between cells I substance unqualified I osmosis of water if in a longer list where other substances are named correctly R osmosis of water if this is the only item noted 3 cell to cell / AW, communication / signalling ; A cell communication 2 Question Answer Marks 5(b)(i) any one from (only) polypeptides / proteins, synthesised at ribosomes ; carbohydrates / polysaccharides, not synthesised at ribosomes ; enzymes, for synthesis / required, not located at ribosomes ; 1 5(b)(ii) exocytosis ; 1 Question Answer Marks 5(c) accept substrate for cellulose and enzyme for cellulase allow use of extracted data to support a response to confirm awarding a mark 1 correct description ; overall trend or more detailed break down e.g. as, cellulose / substrate, concentration increases, rate of reaction increases or as, cellulose / substrate, concentration increases, steep increase in rate of reaction then, less steep increase / (begins to) plateau I ‘rate of reaction is fast and then slows down’ needs ref. to rate of reaction, describing ‘gradient of curve’ is not enough plus any two from 2 increasing cellulose concentration increases number of, collisions between enzyme and substrate / enzyme-substrate complexes / ESCs ; A collisions between active site and substrate A idea of increased chances of cellulose binding to active site 3 at low cellulose concentrations, (many) active sites, available / not all used / not saturated ; 4 at higher cellulose concentrations, active sites becoming saturated / most active sites occupied / most active sites not available / AW ; A actives sites are, saturated / occupied 5 named limiting factor(s), qualified ; e.g. at low(er) cellulose concentrations, cellulose concentration limiting / enzyme concentration not limiting A idea of, not enough cellulose / enzyme in excess as cellulose concentration increases, change from cellulose concentration limiting to enzyme concentration as limiting factor at higher cellulose concentrations, enzyme concentration limiting / cellulose concentration not limiting A idea of, cellulose in excess / not enough enzyme / enzyme working at its fastest rate / active sites not emptying quickly enough for substrate available 3 Question Answer Marks 5(d)(i) mark to max 2 if microorganisms are considered to be enzyme inhibitors lower Km for pectinase, any two from ultrasound increases affinity of enzyme for substrate ; makes shape of active site more complementary ; makes (position of) active site more accessible (to substrate) ; A makes it easier for substrate to enter (active site) breaks up pectin, aggregates / AW, to expose more substrate for binding ; higher Vmax for xylanase, any two from ultrasound increases rate of, collision between enzyme and substrate / more enzyme-substrate complexes per unit time ; I more ESC form needs idea of increased rate increases rate of catalysis after binding ; may change substrate for easier hydrolysis ; may lower, more than normal, activation energy required for reaction ; A described, e.g. increased ability to, break / form, bonds 3 5(d)(ii) yes (as all have) increased, catalytic efficiency / productivity / Vmax /Km ; A manipulated data for increased catalytic efficiency any two from pectin 24.5 / 25% cellulase 17.25 / 17% xylanase 16.8 / 17% 1

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6 The diseases myasthenia gravis (MG) and HIV/AIDS both involve disorders of the immune system. (a) The cause of MG involves a response by B‑lymphocytes. Explain why MG is called a disorder of the immune system. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (b) Studies have indicated that T‑lymphocytes are involved in stimulating the B‑lymphocyte response that causes MG. Research has been carried out on a vaccine that will provide a person with active immunity against these T‑lymphocytes and B‑lymphocytes. Suggest and explain how this vaccine will provide a person with active immunity against the T‑lymphocytes and B‑lymphocytes responsible for causing MG. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [3] (c) Many people who are living with HIV (infected with HIV) develop tuberculosis (TB). If a person does not have any symptoms of TB, one preventive measure is to prescribe antibiotics. This reduces the overall number of cases of TB and deaths from TB. State the disadvantage of prescribing antibiotics as a preventive measure against TB. ................................................................................................................................................... ............................................................................................................................................. [1] (d) Fig. 6.1 is a summary of some of the statistics published by UNAIDS (Joint United Nations Programme on HIV and AIDS) about HIV and HIV/AIDS for the year 2017. The figures shown in Fig. 6.1 for 2017 are estimated. globally, 36.9 million people were living with HIV 1.8 million people became infected with HIV 35.1 million adults and 1.8 million children (under 15 years) 21.7 million were provided with ART (antiretroviral therapy) 940 000 people died from HIV/AIDS 47% of the people provided with ART, while still living with HIV, do not have detectable levels of the virus in their blood Fig. 6.1 One other statistic published by UNAIDS indicated that, in 2017, only 75% of the estimated 36.9 million people living with HIV knew that they had been infected with the virus. With reference to the information in Fig. 6.1, discuss the importance of this statistic. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [3] [Total: 9]

Mark scheme: 6(a) any two from 1 (MG is an) autoimmune, disease / disorder / condition ; A autoimmunity R autoimmune system 2 (disease in which) failure to distinguish / AW, between self and, non-self ; A between self and, non-self / foreign, antigens 3 (so, at neuromuscular junctions) ref. immune response occurs against / antibody produced against, self- antigens / receptors qualified (see list); A antibodies, bind to / block / attack / AW examples of receptors cell surface muscle cell ACh / neurotransmitter neuromuscular junction postsynaptic 4 idea that defective lymphocytes not destroyed (during development) ; Question Answer Marks 6(b) max 2 if wrong context e.g. vaccine contains, foreign antigens / antigens of pathogen / pathogen / antibody to bind to lymphocytes any three from 1 vaccine contains antigens ; in context of antigens of defective, T-lymphocytes and B-lymphocytes (accept antibody of defective B-lymphocyte as AW antigen) 2 stimulates an immune response ; 3 detail ; e.g. macrophages and antigen presentation / AW ref. to specific lymphocytes involved clonal selection of lymphocytes recognition by / activation of, lymphocytes clonal expansion of lymphocytes production of plasma cells in context of B-lymphocytes production of memory cells T-helper cells produce cytokine 4 antibody produced against (defective), T-lymphocytes / B-lymphocytes / antibody (that binds ACh receptors) ; in context of primary or secondary response R if context is related to the vaccine containing antibody 5 memory cells, remain / give long-lasting effect / AW ; 6 memory cells allow secondary immune response to (defective) lymphocytes (newly produced) ; 3 Question Answer Marks 6(c) any one from antibiotic resistance, qualified ; A drug for antibiotic e.g. increases risk of antibiotic resistance developing may cause / could lead to problems of, antibiotic resistance an antibiotic resistant bacterial strain may develop R if, immune / immunity, included R antibiotic resistance / mutation, in, TB / disease / people / virus mutation(s) occur in bacteria which, make antibiotics ineffective / prevent antibiotic action ; A mutation occurs which may make bacteria resistant AVP ; e.g. ref. to development of, DR-TB / MDR-TB / XDR-TB (if latent bacteria become active) 1 Question Answer Marks 6(d) max 2 if not in context of the statistic stated (using only Fig. 6.1) mps 2 -8 only points are in context of people who do not know any three from 1 9.2 million do not know that they are, living / infected with, HIV ; ora 27.7 million people know risk to themselves 2 not accessing, ART / treatment ; A only people who know will access ART A if tested, can access ART 3 high(er) viral, loads / levels (compared to many on ART); ora idea of no control over presence of virus in body 4 greater risk of, developing / dying from, HIV/AIDS / HIV-related diseases ; ora A AIDS for HIV / AIDS R HIV context could be, no ART / higher viral loads / no treatment of HIV-related diseases risk to others 5 greater risk of transmitting, virus / HIV ; ora includes placental transmission R HIV/AIDS or AIDS context could be, higher viral load / not practising prevention 6 detail of prevention that may not be practised ; ora e.g. are sharing contaminated needles are donating blood are breastfeeding are not, practising safe sex / using condoms / AW 7 (may develop opportunistic infection so) greater risk of spreading infectious diseases ; consequence for, health care / authorities 3 Question Answer Marks 6(d) 8 problems with increase in infection within a population ; ora e.g. increased cost of, care / medication increased pressure on medical staff reduction in size of labour force 9 ref. to testing for HIV ; R testing for HIV/AIDS e.g. indicates more, education / advertising, needed to encourage testing indicates more testing required / focusing on at risk groups 10 AVP ; issues for authorities other than mp 8 and 9 e.g. if people do not know status, no contact tracing can occur focus efforts on countries where a high proportion do not know HIV status authorities provide free condoms to try and reduce overall transmission

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