TMJC 2023 H2 P4 Ans

1 CANDIDATE NAME CIVICS GROUP _____________________________________________________________________________ H2 BIOLOGY 9744 Paper 4 Practical 24 August 2023 2 hours 30 minutes Candidates answer on the Question Paper. _____________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Do not open this booklet until you are told to do so. Write your name, civics group and index number on all the work you hand in. Give details of the practical shift and laboratory, where appropriate, in the boxes provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams and graphs. Do not use staples, paper clips, glue or correction fluid/tape. Answer all questions in the spaces provided on the Question Paper. The use of scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of ___ printed pages Shift Laboratory For examiner’s Use 1 / 17 2 / 16 3 / 22 Total / 55 TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Suggested Answers

2 Question 1 You should read throug h the whole of this question carefully and then plan your use of time to make sure that you finish all that you would like to do. Yeast cells are able to respire both aerobically and anaerobically using glucose as a substrate. You are required to investigate the effect of temperature on the rate of respiration of yeast using a respirometer. A simple respirometer can be made by attaching a length of plastic tubing to a 10 cm 3 syringe, using a short section of rubber tubing. The respirometer may be supported with a retort stand and clamp. Fig. 1.1 shows a simple respirometer containing a yeast suspension. Fig. 1.1

3 In order to introduce the yeast suspension into the simple respirometers, the following steps are used: • Remove a sample of the yeast suspension in 20% glucose solution and place it into a boiling tube. • Make sure that the plunger is pushed fully into the barrel of the syringe. • Insert the plastic tubing into the yeast suspension in a boiling tube. • Withdraw the plunger until the yeast suspension reaches the 5 cm 3 mark on the syringe. • Lift the respirometer so that the glass tubing comes out of the yeast suspension. • Keep the apparatus vertical. Slowly withdraw the plunger so that the yeast suspension rises up the plastic tubing until the suspension is near to the top of the plastic tubing (See Fig. 1.1). • Mark the start position of the meniscus of the yeast suspension. Consider a strategy to allow you to compare the effect of temperature on the rate of respiration of yeast,