9700_w13_qp_21
A paper of Biology, 9700
Questions:
6
Year:
2013
Paper:
2
Variant:
1
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1
shows a cell of a female fruit fly, Drosophila melanogaster, during a stage of mitosis. W X Y Name the stage of mitosis shown in . Shade a pair of homologous chromosomes. Name the structure labelled W and state its function. For Examiner’s Use State what happens to structure X and to structure Y between the stage shown in and the end of cell division.
5. The mitotic cell cycle  →  5.2. Chromosome behaviour in mitosis
16. Inheritance  →  16.1. Passage of information from parents to offspring
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2
For Examiner’s Use Table 2.1 shows eight ions that are biologically important. Table 2.1 ammonium (NH4 +) A hydrogen (H+) B hydrogen carbonate (HCO3 –) C iron (Fe2+) D magnesium (Mg2+) E nitrate (NO3 –) F phosphate (PO4 3–) G sulfate (SO4 2–) H Choose one ion to match each of the following statements. In each case write one letter from Table 2.1. You may use each letter (A to H) once, more than once or not at all. A component of polynucleotides. Ion produced by enzyme activity inside red blood cells. Ion used in the production of all amino acids in chloroplasts. Ion that diffuses through carrier proteins with sucrose into companion cells in phloem tissue. Component of haem group in haemoglobin that binds oxygen. For Examiner’s Use The enzyme nitrogenase is found in free-living and symbiotic nitrogen-fixing bacteria. Nitrogenase catalyses the reaction: N2 + 6 e– + 8H+ 2NH4 + Some nitrogenase enzymes have vanadium ions in their active sites; others have molybdenum ions. Explain how the enzyme nitrogenase functions in the fixation of nitrogen. For Examiner’s Use Some pea plants were grown with their roots in a solution of mineral ions. The solution was kept aerated for three days. The concentrations of five ions in the solution and in the root tissue were determined after the three days. The results are shown in Table 2.2. Table 2.2 ion concentration / mmol dm–3 surrounding solution root tissue potassium (K+) 1.0 75.0 magnesium (Mg2+) 0.3 3.5 calcium (Ca2+) 1.0 2.0 phosphate (PO4 3–) 1.0 21.1 sulfate (SO4 2–) 0.3 19.7 With reference to Table 2.2, suggest how cell surface membranes of root cells are responsible for the concentrations of ions in the roots compared to the surrounding solution.
3. Enzymes  →  3.2. Factors that affect enzyme action
7. Transport in plants  →  7.2. Transport mechanisms
14. Homeostasis  →  14.2. Homeostasis in plants
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3
For Examiner’s Use Tuberculosis (TB) and chronic obstructive pulmonary disease (COPD) are diseases that affect the lungs. With reference to TB and COPD, explain how infectious diseases differ from non-infectious diseases. Macrophages are large phagocytic cells that are found in many tissues including alveolar tissue in the lungs. They provide the main means of defence against pathogens in this tissue. is a drawing made from an electron micrograph showing part of a capillary and two alveoli, with a macrophage. macrophage For Examiner’s Use With reference to , explain: how alveoli are adapted for gaseous exchange how macrophages function to protect the lungs from becoming infected. Phagocytes release enzymes that digest proteins. In smokers, this may lead to the large-scale destruction of alveolar walls. Outline the effects of this destruction on a person’s health.
9. Gas exchange  →  9.1. The gas exchange system
11. Immunity  →  11.1. The immune system
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4
For Examiner’s Use Cholesterol is synthesised in the smooth endoplasmic reticulum (SER) in liver cells by a series of enzyme-catalysed reactions. Within the SER, molecules of cholesterol and triglycerides are surrounded by proteins and phospholipids to form lipoproteins. These lipoprotein particles enter the Golgi apparatus where they are packaged into vesicles and pass to the blood. is an electron micrograph of part of a liver cell showing lipoprotein particles within the Golgi apparatus. lipoprotein particle T membrane- bound duct Name structure T in and state its role in liver cells. For Examiner’s Use Suggest why cholesterol is packaged into lipoproteins before release from liver cells into the blood. Explain why cells of the body need to be supplied with cholesterol. Cholesterol is also packaged into vesicles by the SER and then secreted from the cell into small fluid-filled spaces between the liver cells. These spaces form ducts that drain into the gall bladder to form bile. Suggest how cholesterol is secreted into ducts, such as the duct in . State one function of the Golgi apparatus other than the packaging of substances into vesicles for transport.
4. Cell membranes and transport  →  4.1. Fluid mosaic membranes
1. Cell structure  →  1.2. Cells as the basic units of living organisms
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5
For Examiner’s Use Table 5.1 shows the triplets of bases on the template polynucleotide of DNA for some amino acids. Table 5.1 amino acid DNA triplets glutamic acid CTT CTC histidine GTA GTG leucine GAA GAG GAT GAC proline GGA GGG GGT GGC threonine TGA TGG TGT TGC valine CAA CAG CAT CAC shows the base sequences in DNA and mRNA for the first seven amino acids of the β chain of haemoglobin. DNA CAC GAC TGA GGA CTC CTC mRNA GUG CAC CUG CCU GAG GAG β chain val his thr pro glu glu Use Table 5.1 to complete . State the term used to describe the sequence of amino acids in a polypeptide. For Examiner’s Use In sickle cell anaemia, the amino acid at position 6 in the β chain is valine and not glutamic acid. Explain how a single change in the DNA triplet for the sixth amino acid of the gene coding for the β chain leads to the production of a different amino acid sequence.
6. Nucleic acids and protein synthesis  →  6.2. Protein synthesis
6. Nucleic acids and protein synthesis  →  6.1. Structure of nucleic acids and replication of DNA
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6
For Examiner’s Use In some ecosystems, certain species fulfil important roles in maintaining biodiversity in communities. These species are often known as keystone species. The sea otter, Enhydra lutris, is found in waters of the northern and eastern coasts of the Pacific, where it occupies a niche as a predator. These coastal waters are rich in kelp communities. Kelp are very large seaweeds that form ‘underwater forests’. In the 19th century the sea otter was hunted for its fur, with the result that populations decreased. A consequence of this reduction in numbers was the disappearance of much of the kelp. Conservation measures in the 20th century restored the numbers of sea otters. shows the food web for this ecosystem. sharks sea otters large carnivorous fish starfish (sea stars) abalones large crabs small carnivorous fish and invertebrates scallops and sessile invertebrates microscopic floating animals detritus kelp (very large seaweeds) smaller seaweed phytoplankton small herbivorous invertebrates small herbivorous fish sea urchins For Examiner’s Use Explain the meaning of the terms niche and community. niche community With reference to the food web in , suggest why sea otters are considered to be a keystone species. Suggest how the efficiency of energy transfer from kelp to sea urchins could be determined.
18. Classification, biodiversity and conservation  →  18.3. Conservation
18. Classification, biodiversity and conservation  →  18.2. Biodiversity
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