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1 Centre Number Surname Candidate Signature Candidate Number Other Names Notice to Candidate. The work you submit for assessment must be your own. If you copy from someone ese or aow another candidate to copy from you, or if you cheat in any other way, you may be disquaified. Candidate Decaration. I have read and understood the Notice to Candidate and can confirm that I have produced the attached work without assistance other than that which is acceptabe under the scheme of assessment. Date For Teacher s Use Section Mark PSA Stage 1 Skis Stage 2 Skis Section A Genera Certificate of Education Advanced Subsidiary Examination June 2012 Section B TOTAL (max 50) Bioogy BIO3T/Q12/test Unit 3T AS Investigative Skis Assignment Written Test For submission by 15 May 2012 For this paper you must have: the task sheet, your resuts and your cacuations a ruer with miimetre measurements a cacuator. Instructions Use back ink or back ba-point pen. Fi in the es at the top of this page. Answer a questions. You must answer the questions in the space provided. Do not write around each page or on bank pages. Do a rough work in this book. Cross through any work you do not want to be marked. Time aowed 1 hour 15 minutes Information The marks for questions are shown in brackets. The maximum mark for this paper is 34. You wi be marked on your abiity to: use good Engish organise information ceary use scientific terminoogy accuratey. Detais of additiona assistance (if any). Did the candidate receive any hep or information in the production of this work? If you answer yes give the detais beow or on a separate page. Yes No Teacher Decaration: I confirm that the candidateʼs work was conducted under the conditions aid out by the specification. I have authenticated the candidateʼs work and am satisfied that to the best of my knowedge the work produced is soey that of the candidate. Signature of teacher... Date... As part of AQA s commitment to assist students, AQA may make your coursework avaiabe on a stricty anonymous basis to teachers, examining staff and students in paper form or eectronicay, through the internet or other means, for the purpose of indicating a typica mark or for other educationa purposes. In the unikey event that your coursework is made avaiabe for the purposes stated above, you may object to this at any time and we wi remove the work on reasonabe notice. If you have any concerns pease contact AQA. To see how AQA compies with the Data Protection Act 1988 pease see our Privacy Statement at aqa.org.uk. BIO3T/Q12/test

2 2 Section A These questions are about your investigation of the effect of substrate concentration on the rate of an enzyme-controed reaction. Use your Task Sheet and your resuts tabe and graph to answer them. Answer a questions in the spaces provided. Do not write 1 You were tod to remove the card from the cataase extract and shake off any surpus iquid (step 3). Expain why it is necessary to shake off surpus iquid. 2 It woud have been better if you had kept temperature and ph constant in this investigation. 2(a) Describe how you coud keep temperature constant. 2(b) Describe how you coud keep ph constant. (1 mark)

3 3 Do not write 3 You were tod to repeat the measurements at each concentration of hydrogen peroxide (step 7). How many repeats did you carry out at a concentration of 100% hydrogen peroxide? Expain why you carried out this number of repeats. Number of repeats... Expanation... (1 mark) 4 In this investigation, you found the time taken for the card to rise to the surface. Expain why this is a vaid measure of the rate of the reaction. (3 marks) (Extra space)... Turn over

4 4 Do not write 5 Another student carried out the same investigation as you did. She obtained the resuts shown in the graph Rate at which card rose to the surface as 1 / time in seconds Percentage concentration of hydrogen peroxide 5(a) Describe the resuts that the student obtained. 5(b) What factor imited the rate of reaction between hydrogen peroxide concentrations of 0% and 30%? Give the evidence for your answer. Factor... Evidence...

5 5 Do not write 6 A student carried out a simiar investigation to yours. He decided to carry out repeats using the same piece of card in the same tube. Each time the card reached the surface, he immediatey pushed it back down again. He noticed that the card took onger to return to the surface each time. Expain why the card took onger to return to the surface. 15 Turn over for the next question Turn over

6 6 Resource Sheet Resource A Cataase is used in a number of industria processes. It is normay obtained from a fungus caed Aspergius niger. Scientists produced a mutant strain of A. niger caed K30. They wanted to know if this mutant strain produced more cataase than the norma strain of A. niger. The scientists grew sampes of the norma strain of the fungus and of the K30 strain on jey in separate Petri dishes. The jey contained a bue substance which is turned coouress by cataase. They incubated the dishes for 3 days then measured the diameter of the coouress zone around the fungus. They cacuated the ratio of the diameter of the coouress zone to the diameter of the fungus. The diagram shows the dishes after incubation. Norma strain Jey containing bue substance Coouress zone Fungus K30 strain

7 7 Resource B Some of the cataase produced by Aspergius niger is intraceuar and some is extraceuar. Intraceuar enzymes stay inside the ces that produce them. Extraceuar enzymes are secreted from the ces that produce them. Another group of scientists grew a different strain of A. niger. A. niger grows from tiny structures caed spores. The scientists kept the spores in an isotonic medium at a ow temperature unti they needed them. They put spores of A. niger into a 500 cm 3 fask containing a sterie medium. The medium contained starch. They measured the tota amount of cataase and the amount of extraceuar cataase produced by the fungus over a period of 100 hours. The graph shows their resuts. Cataase concentration / units dm Tota cataase Extraceuar cataase Time / h Turn over

8 8 Do not write Section B Use the information in the Resource Sheet and your own knowedge to answer the questions. Use Resource A to answer Questions 7 to 9. Answer a questions in the spaces provided. 7 The scientists grew both strains of fungi on dishes kept at 30 ºC. Keeping the dishes at a temperature of 15 ºC woud affect the resuts. Use your knowedge of kinetic energy to expain why. 8(a) The scientists gave their resuts as ratios. Expain the advantage of giving the resuts of this investigation as a ratio. 8(b) For the norma strain the ratio of the diameter of the coouress zone to the diameter of the fungus was 1.1 : 1. Cacuate the ratio of the diameter of the coouress zone to the diameter of the fungus for the K30 strain. Show your working. Ratio =...

9 9 Do not write 9 The cataase produced by the K30 strain of the fungus is mainy an extraceuar enzyme. This means that the fungus secretes cataase from its ces into the jey in the Petri dish. Describe and expain the evidence from the investigation which shows that the cataase is an extraceuar enzyme. Use Resource B to answer Questions 10 to (a) The scientists kept the spores in an isotonic medium unti they were needed. Suggest why it was important that the medium was isotonic. 10 (b) The scientists kept the spores at a ow temperature unti they were needed. Suggest why. (1 mark) Turn over

10 10 Do not write 11 Starch is a source of carbon, hydrogen and oxygen for the fungus. Name one other chemica eement that must be in the cuture medium before A. niger can synthesise cataase. Give the reason for your answer. Chemica eement... Reason To get reiabe resuts in this investigation, the medium must be sterie. Expain why. 13 (a) At what time was the concentration of intraceuar cataase highest? (1 mark) 13 (b) Between what times was the rate of tota cataase production highest? (1 mark)

11 11 Do not write 14 Technoogists prefer to manufacture extraceuar enzymes rather than intraceuar enzymes. This is because intraceuar enzymes are more expensive to purify than extraceuar enzymes. Suggest why intraceuar enzymes are more expensive to purify. 19 END OF QUESTIONS Copyright 2012 AQA and its icensors. A rights reserved.