9700_s12_qp_21
A paper of Biology, 9700
Questions:
6
Year:
2012
Paper:
2
Variant:
1
Login to start this paper & get access to powerful tools
1
For Examiner’s Use Name as precisely as you can the structure described in each of the following statements. The blood vessel that transports deoxygenated blood from the heart. The cell that ingests and digests cell debris and bacteria in the lungs. The cell that secretes antibodies. The epithelial cell that secretes mucus in the trachea. The tissue that prevents the collapse of the trachea during inhalation.
9. Gas exchange  →  9.1. The gas exchange system
8. Transport in mammals  →  8.1. The circulatory system
Open
2
For Examiner’s Use shows a drawing made from an electron micrograph of two adjacent cells in a leaf. A B C D E F G vacuole Structures A and B are both visible using the light microscope, but the internal detail of these organelles shown in is only visible using the electron microscope. Explain why the internal details of structures A and B are only visible when using the electron microscope and not when using the light microscope. For Examiner’s Use Name in full the structures labelled C, D and E. C D E State one role of vacuoles in plant cells. Structures F and G have very different permeability properties. Explain how the composition of structures F and G determines the permeability properties of these structures. shows two plasmodesmata connecting the adjacent cells. Describe the roles of plasmodesmata in transport in plants.
4. Cell membranes and transport  →  4.2. Movement into and out of cells
7. Transport in plants  →  7.1. Structure of transport tissues
Open
3
For Examiner’s Use Haemoglobinopathies are inherited conditions linked to the structure and function of haemoglobin. Sickle cell anaemia is one of these conditions in which the transport and delivery of oxygen to tissues is less than normal. An investigation was carried out to discover the effect of sickle cell anaemia on the ability of blood to carry oxygen. Blood samples were taken from two people: • person L without sickle cell anaemia • person M with sickle cell anaemia. The percentage saturation of haemoglobin with oxygen was determined over a range of partial pressures of oxygen. shows oxygen haemoglobin dissociation curves for the two blood samples. partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen M L P50 is the partial pressure of oxygen at which haemoglobin is 50% saturated with oxygen. It is taken as a measurement of the affinity of haemoglobin for oxygen. State the P50 for the two blood samples, L and M. L M For Examiner’s Use With reference to , describe how the dissociation curve for person M differs from the dissociation curve for person L. Explain the advantage of the position of the dissociation curve for people with sickle cell anaemia. The partial pressure of oxygen in the lungs at sea level is about 13.5 kPa. At an altitude of 3000 metres the partial pressure of oxygen in the lungs is about 7.5 kPa. When people move from sea level to high altitude they become adapted to the low partial pressure of oxygen. Describe and explain how humans become adapted to the low partial pressure of oxygen at high altitude. For Examiner’s Use Vaccination is used to control the spread of diseases, such as measles. Explain why vaccination cannot be used to prevent sickle cell anaemia.
8. Transport in mammals  →  8.2. Transport of oxygen and carbon dioxide
16. Inheritance  →  16.2. The roles of genes in determining the phenotype
Open
4
For Examiner’s Use Penicillin is an antibiotic that interferes with the synthesis of cell walls in bacteria. Even before penicillin became widely available in the 1940s, the enzyme penicillinase which breaks down penicillin had been isolated. This enzyme is now found in many bacteria and gives them resistance to penicillin. is a ribbon model of the structure of the enzyme penicillinase. The arrow indicates the active site of the enzyme. Explain why the shape of the active site of an enzyme, such as penicillinase, is important. For Examiner’s Use With reference to , identify the aspects of protein structure that are shown and those that are not shown. aspects of protein structure shown aspects of protein structure not shown shows the changes in energy during the progress of an uncatalysed reaction. progress of the reaction energy Draw on a curve to show changes in energy during the progress of the same reaction when catalysed by an enzyme. State the term given to the energy level that must be overcome before a reaction can progress. For Examiner’s Use Antibiotic resistance is a serious worldwide problem. Suggest how antibiotics can be used effectively to avoid the development of widespread resistance in bacteria.
3. Enzymes  →  3.1. Mode of action of enzymes
10. Infectious diseases  →  10.2. Antibiotics
Open
5
For Examiner’s Use The slime mould, Dictyostelium discoideum, is a eukaryote and a decomposer of protein-rich material. shows the life cycle of D. discoideum. X Y spores spores amoeboid cells fusion of amoeboid cells aggregation of amoeboid cells State the type of nuclear division that occurs at X and at Y. X Y State what is meant by the term reduction division and explain why this division is necessary in a life cycle, such as that shown in . For Examiner’s Use The amoeboid cells of D. discoideum feed on protein-rich material and break it down to form ammonium ions (NH4 +). The cell membranes of D. discoideum have transporter proteins that are responsible for the excretion of ammonium ions. Describe what happens to the ammonium ions excreted by D. discoideum into the soil. Suggest why a transporter protein is required for the removal of ammonium ions from D. discoideum.
16. Inheritance  →  16.1. Passage of information from parents to offspring
4. Cell membranes and transport  →  4.2. Movement into and out of cells
Open
6
For Examiner’s Use shows part of a DNA molecule. O O O P O O O O P O O O O P O O O P O O O O ¯ ¯ ¯ O¯ ¯ ¯ O P O O O O P O O O O O N N N N N H H H H3C N N N H H H H H O O O O O O O N N N A C G T A = adenine C = cytosine G = guanine T = thymine Key: N N N N Complete by drawing on the hydrogen bonds between the two base pairs shown. State the importance of hydrogen bonding in DNA structure. For Examiner’s Use In the 1950s, Erwin Chargaff determined the relative quantities of the four bases in DNA in different organisms. His results provided important evidence for the model of DNA proposed by James Watson and Francis Crick in 1953. Some of Chargaff’s data is shown in Table 6.1. Table 6.1 organism percentage of adenine percentage of thymine percentage of guanine percentage of cytosine Escherichia coli 24.7 23.6 26.0 25.7 a yeast 31.3 32.9 18.7 17.1 wheat 27.3 27.1 22.7 22.8 octopus 33.2 31.6 17.6 17.6 sea urchin 32.8 32.1 17.7 17.3 chicken 28.0 28.4 22.0 21.6 human 29.3 30.0 20.7 20.0 With reference to , explain how the data in Table 6.1 helps to confirm the arrangement of bases in DNA. For Examiner’s Use Table 6.2 shows Chargaff’s data for a virus. Table 6.2 organism percentage of adenine percentage of thymine percentage of guanine percentage of cytosine a virus 24.0 31.2 23.3 21.5 State how the result for the virus differs from the results for all the organisms given in Table 6.1. Suggest why the results for the virus are different from all the other organisms.
6. Nucleic acids and protein synthesis  →  6.1. Structure of nucleic acids and replication of DNA
Open