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GCE May 2008 : (A2 3A) Synoptic Paper

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2008 Biology assessing Module 6A: Synoptic Paper A2B31 Assessment Unit A2 3A [A2B31] TUESDAY 27 MAY, AFTERNOON TIME 1 hour. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Write your answers in the spaces provided in this question paper. Answer all four questions. INFORMATION FOR CANDIDATES The total mark for this paper is 50. Section A carries 35 marks. Section B carries 15 marks. You should spend approximately 20 minutes on Section B. You are expected to answer Section B in continuous prose. Quality of written communication will be assessed in Section B. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. A data sheet is provided for use with this paper. A2B3AS8 3771 For Examiner s use only Question Number 1 2 3 4 Total Marks Marks Section A Examiner Only Marks 1 Remark The aquatic filamentous cyanobacterium (blue-green alga) Anabaena is a photosynthetic prokaryote capable, under certain conditions, of nitrogen-fixation. A filament of Anabaena is shown in the diagram below approximately 10 vegetative cells separate heterocysts. vegetative cells heterocysts Photosynthesis is confined to the vegetative cells, while heterocysts are specialised for nitrogen-fixation and cannot themselves photosynthesise. (a) The conditions required for production of heterocysts was investigated by culturing Anabaena in a medium containing nitrate for 24 hours. Following this, the culture was washed and added to a medium lacking nitrate for a further 24 hours. The results are shown in the graph below. Nitrate available Percentage of cells which are heterocysts/% 10 No nitrate in the medium 5 0 0 A2B3AS8 3771 4 8 12 16 20 28 24 Time/h 2 32 36 40 44 48 [Turn over (i) Suggest why cultures had CO2 bubbled through them throughout the investigation. Examiner Only Marks Remark _____________________________________________________ __________________________________________________ [1] (ii) Describe the trends shown in the graph opposite and suggest explanations for these. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ __________________________________________________ [4] (b) Nitrogen-fixation cannot take place in aerobic conditions since the enzyme system involved is inhibited by oxygen. Suggest why nitrogenfixation is confined to heterocysts in Anabaena. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] A2B3AS8 3771 3 [Turn over (c) Lough Neagh is a eutrophic lake and has relatively high levels of nitrate. Suggest two reasons for this. Examiner Only Marks Remark 1. _______________________________________________________ _________________________________________________________ 2. _______________________________________________________ ______________________________________________________ [2] (d) Anabaena is a prokaryote. Note two features of prokaryotic cells. 1. _______________________________________________________ _________________________________________________________ 2. _______________________________________________________ ______________________________________________________ [2] A2B3AS8 3771 4 [Turn over BLANK PAGE (Questions continue overleaf) A2B3AS8 3771 5 [Turn over 2 The metabolic rate of each of four groups of 20 volunteers was measured in the following conditions. Examiner Only Marks Remark Sitting Walking (at 3 miles per hour) Jogging (at 6 miles per hour) Cycling (at 16 miles per hour) From the data for each group, the mean metabolic rate and standard deviation of the mean were calculated and, for three of the groups, the 95% confidence limits were determined. The means and 95% confidence limits are shown in the graph below. 4000 Metabolic rate/kJ h 1 3000 2000 1000 0 Sitting Walking (3 mph) Jogging (6 mph) Cycling (16 mph) (a) For the group of 20 volunteers who were walking the mean was 1260, while the standard deviation of the mean ( x) was 90.8. (Units 1.) are kJ h Calculate the 95% confidence limits, and plot these on the graph. (Use the space below to show your working.) Upper limit _____________ Lower limit _____________ [3] A2B3AS8 3771 6 [Turn over (b) Identify which of the means of the four groups is the most reliable and which the least reliable. Explain your reasoning. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (c) The variable investigated was exercise. However, a number of other factors will have influenced the variability of the results within each group of volunteers. Suggest two factors which would have caused differences in the metabolic rate of individuals. 1. _______________________________________________________ 2. ____________________________________________________ [2] (d) Compare the means and confidence limits for jogging and cycling . Do these suggest that there is a significant difference in their mean metabolic rate? Explain your reasoning. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (e) Suggest one health advantage of cycling over jogging. _________________________________________________________ ______________________________________________________ [1] (f) Suggest one health advantage of exercise. _________________________________________________________ ______________________________________________________ [1] A2B3AS8 3771 7 [Turn over 3 Read the passage below and then use the information in the passage, and your own understanding, to answer the questions which follow. Viruses consist of nucleic acid contained within a protective protein coat called a capsid. They infect a wide variety of organisms, both eukaryotes (animals, fungi and plants) and prokaryotes (bacteria). Viral species will contain either DNA or RNA, which may be either single- or double-stranded, depending on the species. Therefore, viruses as a group contain all four possible types of nucleic acid: double-stranded DNA, single-stranded DNA, double-stranded RNA and single-stranded RNA. Animal viral species may possess all combinations, whereas plant viruses tend to have single-stranded RNA. Bacterial viruses tend to have double-stranded DNA. Viruses enter a host cell following the attachment of a capsid protein with a specific receptor on a cell-surface membrane. They then use the machinery and metabolism of the host cell to replicate. Host cells will be induced by the virus to begin manufacturing capsid proteins while the virus must also direct the replication of viral nucleic acid. The technique for this depends heavily on the type of nucleic acid. After the nucleic acid has been replicated and capsids assembled, new viruses may be released. The influenza A virus has a particular capsid protein, haemagglutinin, which attaches to specific receptors on the epithelial cells of the respiratory tract. The haemagglutinin is not only responsible for entry into the host cell, but acts as the viral antigen recognised by the host s immune system. Following a major epidemic of flu, most people will be immune to the virus strain. The influenza virus contains single-stranded RNA, which will readily mutate to cause amino acid substitutions in haemagglutinin. Although these minor changes in haemagglutinin do not prevent it attaching to host cells, its antigenic properties are sufficiently altered to make the immune system ineffective in recognising it, and so leave the host susceptible to a new infection of flu. 5 10 15 20 25 Examiner Only (a) What name is given to viruses which infect bacteria [line 3]? Marks Remark ______________________________________________________ [1] (b) Viruses may contain either DNA or RNA which may be either singleor double-stranded [line 4/5]. Suggest a mechanism by which singlestranded RNA may be replicated. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] A2B3AS8 3771 8 [Turn over (c) Describe, concisely, the machinery and metabolism of a host cell which is used to manufacture viral proteins. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [3] (d) Outline how the immune system operates to attack viral infections, both the viral-infected cells and free viruses in the body. (i) Viral-infected cells _____________________________________________________ _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (ii) Free viruses _____________________________________________________ _____________________________________________________ _____________________________________________________ __________________________________________________ [2] (e) Explain how a mutation in the influenza virus could cause an amino acid substitution in haemagglutinin. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] A2B3AS8 3771 9 [Turn over (f) Explain why it has been difficult to develop an effective influenza vaccine. Examiner Only Marks Remark _________________________________________________________ ______________________________________________________ [1] A2B3AS8 3771 10 [Turn over Section B Examiner Only Marks Remark You are expected to answer the following question in continuous prose. Diagrams may be used, but you should make sure that they are relevant and add extra information to your account. It will be marked for its biological content, coverage of the topic, and the quality of written communication. In this question up to two marks are awarded for the quality of written communication. 4 [2] Write an account of the release, capture and transfer of energy in biological systems. Your account should show understanding of, at least, three topics which you have studied. [13] ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ A2B3AS8 3771 11 [Turn over Examiner Only ____________________________________________________________ Marks Remark ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ A2B3AS8 3771 12 [Turn over Examiner Only ____________________________________________________________ Marks Remark ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ A2B3AS8 3771 13 [Turn over Examiner Only ____________________________________________________________ Marks Remark ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ A2B3AS8 3771 14 [Turn over THIS IS THE END OF THE QUESTION PAPER A2B3AS8 3771 15 S 6/07 529-023-1

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Additional Info : Gce Biology May 2008 Assessment Unit A2 3A Module 6A: Synoptic Paper
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

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