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GCE JUN 2009 : (AS 1) Cell Biology - Revised

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Sp ec Ne i w ca tio n Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2009 Biology assessing Module 1: Cell Biology AB111 Assessment Unit AS 1 [AB111] MONDAY 1 JUNE, AFTERNOON TIME 1 hour 30 minutes. 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. Write your answer to Section B on the lined paper at the end of this booklet. Answer all eight questions. You are provided with Photograph 1.5 for use with Question 5 in this paper. Do not write your answers on this photograph. INFORMATION FOR CANDIDATES The total mark for this paper is 75. Section A carries 60 marks. Section B carries 15 marks. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. You are reminded of the need for good English and clear presentation in your answers. Use accurate scientific terminology in all answers. 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, and awarded a maximum of 2 marks. 4941 For Examiner s use only Question Marks Number 1 2 3 4 5 6 7 8 Total Marks Section A Examiner Only Marks 1 Remark The ileum is an organ which makes up part of the mammalian digestive system. (a) (i) Why can the ileum be described as an organ? __________________________________________________________ _______________________________________________________ [1] (ii) Why can the digestive system be described as a system? __________________________________________________________ _______________________________________________________ [1] (b) Describe the role of the following structures in the functioning of the ileum. muscularis mucosa ______________________________________________________________ ______________________________________________________________ goblet cells ______________________________________________________________ ______________________________________________________________ muscularis externa ______________________________________________________________ ______________________________________________________________ [3] 4941 2 [Turn over 2 -glucose molecules can be linked together to form the helical and branched polysaccharide, amylopectin Examiner Only Marks Remark (a) State what type of reaction occurs when one glucose molecule bonds with another glucose molecule. ___________________________________________________________ [1] (b) State which carbon atoms in adjacent glucose molecules are linked to produce a branch in amylopectin. ___________________________________________________________ [1] (c) Describe an advantage of amylopectin having many branches. ___________________________________________________________ [1] (d) Name another branched polysaccharide. ___________________________________________________________ [1] (e) (i) Name a biochemical test that could be used to distinguish glucose from polysaccharide molecules. _______________________________________________________ [1] (ii) Describe the biochemical test you have named. __________________________________________________________ _______________________________________________________ [1] (iii) Describe the result of the above test that would allow you to distinguish glucose from polysaccharides. __________________________________________________________ _______________________________________________________ [1] 4941 3 [Turn over 3 The diagram below represents the fluid mosaic model of membrane structure and three mechanisms (labelled 1, 2 and 3) by which substances may move across the membrane. The concentration gradient across the membrane is also shown. Examiner Only Marks Remark A concentration gradient energy Mechanism 1 Mechanism Mechanism 2 3 (a) Identify the structure labelled A. _______________________________ [1] (b) Identify each mechanism of membrane transport and, in each case, give a reason for your identification. (i) Mechanism 1 Identification ______________________________________________ Reason ___________________________________________________ _______________________________________________________ [2] (ii) Mechanism 2 Identification _____________________________________________ Reason ___________________________________________________ _______________________________________________________ [2] 4941 4 [Turn over (iii) Mechanism 3 Examiner Only Marks Remark Identification ______________________________________________ Reason ___________________________________________________ _______________________________________________________ [2] (c) Mechanism 1 involves two different paths across the membrane. Explain why there are two paths for this mechanism of membrane transport. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ _____________________________________________________________ [2] 4941 5 [Turn over 4 The graph below shows changes in both cell mass and DNA mass per nucleus during several mitotic cell cycles in a mammalian embryo. Examiner Only Marks Remark X s as m ell DNA mass per nucleus /arbitrary units c 2 1 DNA mass per nucleus 1 0 Cell mass/arbitrary units 2 0 0 12 24 Time/hours 36 48 (a) Between which times shown on the graph does the G1 phase (first growth phase) occur during the first cell cycle? ___________________________________________________________ [1] (b) State what is occurring during the phase indicated by X on the graph. ___________________________________________________________ [1] (c) Explain the changes in the DNA mass per nucleus during one cell cycle. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ _____________________________________________________________ [3] 4941 6 [Turn over (d) The DNA mass per nucleus during a meiotic cell cycle follows a similar pattern to that shown opposite, but with one major difference. Describe and explain this difference. Examiner Only Marks Remark ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ _____________________________________________________________ [2] 4941 7 [Turn over 5 Photograph 1.5 is an electron micrograph showing part of two neighbouring plant cells. Examiner Only Marks Remark (a) Identify the features labelled A to D. A __________________________________________________________ B __________________________________________________________ C __________________________________________________________ D _______________________________________________________ [4] (b) The magnification of the photograph is 32 000. Calculate the actual diameter (in m) of the organelle along the line XY in the photograph. (Show your working in the space below.) Answer _______________ [2] (c) Suggest one piece of evidence visible in the photograph that would suggest that these cells are from the spongy mesophyll layer of a leaf. ______________________________________________________________ _____________________________________________________________ [1] 4941 8 [Turn over BLANK PAGE (Questions continue overleaf) 4941 9 [Turn over 6 An experiment was undertaken to investigate the effect of pH on two proteolytic enzymes, enzyme 1 and enzyme 2. Cubes of protein, each of 200 mg mass, were placed in solutions of each enzyme at different pHs, and the time taken for the protein to be digested was measured. The results are shown in the table below. pH of reaction mixture Examiner Only Marks Remark Time for protein to be digested/minutes Enzyme 1 Enzyme 2 1 80 2 50 3 7 4 55 80 5 72 65 6 80 52 7 32 8 20 9 42 10 71 11 80 (a) Plot the above data, using the most appropriate graphical technique. (Use the graph paper opposite.) [6] (b) (i) Suggest how the pH in each reaction mixture would have been maintained. _______________________________________________________ [1] (ii) State one factor that should have been controlled in the experiment and explain the influence of that factor on enzyme activity. Factor ____________________________________________________ Influence _________________________________________________ _______________________________________________________ [2] (c) Using the information in your graph, calculate the rate of reaction for enzyme 1 at pH 2 in units of mg hour 1. (Show your working.) Answer _____________ [2] 4941 10 [Turn over 4941 11 [Turn over (d) Which of the two enzymes would normally be found in the mammalian stomach? Explain your answer. Examiner Only Marks Remark ______________________________________________________________ _____________________________________________________________ [1] (e) State the pH range over which both enzymes are active. _____________________________________________________________ [1] 4941 12 [Turn over BLANK PAGE (Questions continue overleaf) 4941 13 [Turn over 7 The diagram below represents the processes involved in the polymerase chain reaction (PCR). This technique allows forensic scientists to analyse and potentially match DNA samples left at the scene of a crime. Examiner Only Marks Remark Original DNA to be amplified 3 5 5 3 Step 1 Excess primer 3 5 Heated to separate strands and primers added Primer 2 Primer 1 5 3 Step 2 3 5 5 3 Step 3 Replication completed 3 5 5 3 (a) What advantage does PCR offer to forensic scientists? _____________________________________________________________ [1] (b) (i) In step 1, what is the purpose of heating the DNA sample to 95 C? __________________________________________________________ __________________________________________________________ _______________________________________________________ [2] (ii) Primers, each containing roughly twenty bases are also added to the DNA sample in step 1. What is the purpose of these primers in the process? __________________________________________________________ _______________________________________________________ [1] (iii) Name the enzyme that would be added to the DNA sample in step 2. _______________________________________________________ [1] 4941 14 [Turn over (iv) What else should be added to the process in step 2 to allow successful replication of the DNA sample? Examiner Only Marks Remark _______________________________________________________ [1] (c) In step 3, replication of the DNA is completed. Describe the sequence of events, following the separation of the DNA strands in step 1, which lead to the DNA being replicated. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ _____________________________________________________________ [3] The heating of the DNA sample to 95 C in step 1 could denature the enzymes involved. (d) (i) Describe precisely how high temperatures could denature the enzymes. __________________________________________________________ _______________________________________________________ [1] (ii) Suggest how scientists have solved this potential problem. __________________________________________________________ _______________________________________________________ [1] (e) In some legal cases, the use of PCR has been discredited. Suggest one possible source of error in the PCR process. ______________________________________________________________ _____________________________________________________________ [1] 4941 15 [Turn over Section B Examiner Only Marks 8 Remark Give an account of the process of osmosis and its effect in animal and plant cells. [15] _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ 4941 16 [Turn over _________________________________________________________________ Examiner Only Marks Remark _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ 4941 17 [Turn over _________________________________________________________________ Examiner Only Marks Remark _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ 4941 4941 18 [Turn over THIS IS THE END OF THE QUESTION PAPER 4941 19 938-033-1 [Turn over Sp ec Ne ifi w ca tio n GCE Biology Advanced Subsidiary (AS) Assessment Unit AS 1 Module 1: Cell Biology Summer 2009 Photograph 1.5 (For use with Question 5) A B X Y 4941.02 D Source: Marilyn Schaller/Science Photo Library 30 m AB111INS1 C

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Additional Info : Gce Biology June 2009 Assessment Unit AS 1 Module 1: Cell Biology - Revised
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