9700_w23_qp_23
A paper of Biology, 9700
Questions:
6
Year:
2023
Paper:
2
Variant:
3
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1
The malarial pathogen, Plasmodium falciparum, enters red blood cells after a person becomes infected. After some time, each cell of P. falciparum divides to form daughter cells. shows a cell of P. falciparum that is forming many daughter cells. cell surface membrane of red blood cell nucleus With reference to , suggest how the presence of P. falciparum affects a red blood cell. When P. falciparum divides there is unequal division of the cytoplasm to form small, genetically identical daughter cells. Outline the events that occur in the cell of P. falciparum to form the daughter cells shown in . In 2013, the World Health Organization (WHO) set a target for researchers to create a vaccine for malaria. WHO required the vaccine to show 75% efficacy and be ready for use by 2030. Efficacy is a measure of the effectiveness of a vaccine in reducing the number of new cases of malaria. A trial of the R21/Matrix‑MTM vaccine in Burkina Faso in 2020 achieved a 77% efficacy over a 12‑month period. A control group received a vaccine for rabies. Vaccines stimulate an immune response with the production of antibodies. Explain how antibodies will reduce the spread of the malarial pathogen through the bloodstream. Some vaccination programmes have been more successful than others. Discuss the factors that contribute to the success of a vaccination programme.
10. Infectious diseases  →  10.1. Infectious diseases
11. Immunity  →  11.2. Antibodies and vaccination
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2
Glucose is used in the synthesis of amylose. Glucose is first converted to glucose 1‑phosphate (G 1‑P). Starch phosphorylase is an intracellular enzyme that can catalyse the synthesis of amylose from G 1‑P, which is the substrate for the reaction: (glucose 1‑phosphate)n amylose + (phosphate ions)n n = a large number Students used a colorimeter to investigate the progress of the reaction. The students made a reaction mixture containing 0.01 mol dm–3 G 1‑P in a buffer solution at pH 6.0. A very small quantity of amylose was added to initiate the reaction. A solution of starch phosphorylase was added to the reaction mixture and samples were taken at 1‑minute intervals. Each sample was added to a dilute iodine solution, stirred and then poured into a cuvette. The absorbance of each solution was recorded. The results of the investigation are shown in . 0.00 0.20 0.40 0.60 0.80 1.00 absorbance 1.20 1.40 1.60 1.80 2.00 time after addition of starch phosphorylase / min Explain why the absorbance increases, as shown in . The students took their final sample at 12 minutes. Predict the results for absorbance if the students had continued to take samples for a further 10 minutes. Explain your answer. prediction explanation State an advantage of using a colorimeter in determining the progress of the reaction. The reaction catalysed by starch phosphorylase occurs at the ends of amylose molecules. Describe the sequence of events that occurs when starch phosphorylase catalyses the addition of a molecule of glucose to the end of an amylose molecule.
3. Enzymes  →  3.1. Mode of action of enzymes
2. Biological molecules  →  2.1. Testing for biological molecules
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3
Haemoglobin is a complex protein molecule made of four separate subunits, as shown in . P The shading represents the two different polypeptides that form a molecule of haemoglobin. State the names of the two different polypeptides. Identify the structure labelled P in . shows some of the levels of protein structure. State the level of protein structure that is not shown in . Haemoglobin is involved in the transport of carbon dioxide. Molecules of carbon dioxide enter red blood cells as the cells travel in capillaries through muscle tissue. Some of these molecules are converted to carbonic acid. Explain how haemoglobin is involved in the transport of carbon dioxide molecules that are not converted to carbonic acid. When haemoglobin associates with oxygen it forms oxyhaemoglobin. State the precise site in the mammalian body where haemoglobin molecules bind with oxygen. The compound 2,3‑diphosphoglycerate (2,3‑DPG) is produced in red blood cells. 2,3‑DPG binds to haemoglobin and stabilises it. shows oxygen dissociation curves when red blood cells have high and low concentrations of 2,3‑DPG. percentage saturation of haemoglobin with oxygen partial pressure of oxygen / kPa low concentration of 2,3-DPG high concentration of 2,3-DPG P50 is the partial pressure of oxygen when haemoglobin is 50% saturated. The P50 is used to compare the affinity of haemoglobin for oxygen under different conditions. Use the information in to describe the effect of an increase in the concentration of 2,3‑DPG on the oxygen dissociation curve. Blood is stored in blood banks for use in hospitals during operations. The concentration of 2,3‑DPG in red blood cells decreases when blood is stored in a blood bank. State and explain the effect that the use of blood taken from a blood bank has on the supply of oxygen to the tissues of a person during an operation.
8. Transport in mammals  →  8.2. Transport of oxygen and carbon dioxide
2. Biological molecules  →  2.3. Proteins
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4
is a diagram showing the transcription of part of the COL1A2 gene that codes for a collagen polypeptide. The part of the COL1A2 gene shown is a section of exon. Structure A represents an enzyme involved in transcription. C T C U U U T T A A G A A A T C A A G A G G T G T A A A G C T A A T C G T A C G C G A U C G A U T A T T A C T G 5' 5' 3' 3' transcribed strand non-transcribed strand primary transcript A Name the enzyme labelled A in . Name the bond that forms between the nucleotides in the primary transcript. State the number of amino acids that are coded for by the sequence of nucleotides on the primary transcript shown in . Use the information in to explain why one of the strands of DNA is not transcribed. New mitochondria are formed when a mitochondrion divides into two. is a transmission electron micrograph of a mitochondrion that is dividing. magnification ×50 000 State two features of mitochondria that are visible in . The line on shows the diameter of one of the mitochondria. Calculate the actual diameter of the mitochondrion. Give your answer to one significant figure. answer = μm Mitochondrial DNA codes for some polypeptides of proteins used within the mitochondrion. Some of the proteins allow movement of ions into and out of the mitochondria. Outline the ways in which ions can move into mitochondria.
6. Nucleic acids and protein synthesis  →  6.2. Protein synthesis
12. Energy and respiration  →  12.2. Respiration
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5
In flowering plants, transport of assimilates occurs in phloem tissue between sources and sinks. Explain why a root can be a source and a sink. State two examples of assimilates that are transported in the phloem. Describe and explain the mechanism that is responsible for the movement of phloem sap in sieve tubes. Tobacco mosaic virus (TMinfects many crop plants. The virus passes between cells in the leaves and can travel throughout plants in the phloem. The enzyme pectin methylesterase (PME) is involved with the production of cell walls. The enzyme is also known to influence the movement of TMV through plants. Scientists investigated the effect of PME on the transport of TMV through plants. The scientists used three varieties of tobacco plants. Two varieties, V1 and V2, have small quantities of PME. A third variety, C, has the normal quantity of PME and was used as the control in this investigation. The plants in each group were infected with TMV at the same time. The accumulation of the virus particles transported to the leaves at the top of the plants was determined over 36 days. The results are shown in . The arrow indicates when all the plants were infected with TMV. time / days after infection with TMV TMV accumulation in leaves at the top of the plants / percentage of maximum number of virus particles in control plants C V1 V2
7. Transport in plants  →  7.2. Transport mechanisms
7. Transport in plants  →  7.1. Structure of transport tissues
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6
The boundaries and names shown, the designations used and the presentation of material on any maps contained in this question paper/insert do not imply official endorsement or acceptance by Cambridge Assessment International Education concerning the legal status of any country, territory, or area or any of its authorities, or of the delimitation of its frontiers or boundaries. The mammalian heart consists of four chambers. Explain why the ventricles have thicker walls than the atria. Complete Table 6.1 to identify the structure in the heart responsible for each function listed. Table 6.1 function structure in the heart initiates the heartbeat delays the wave of depolarisation between the atria and the ventricles transmits the wave of depolarisation through muscles of the ventricle closes when the left ventricle contracts
8. Transport in mammals  →  8.3. The heart
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