WJEC Biology for A2 Level: Revision Workbook

Q3 [AO3, AO1] An experiment was carried out to investigate the effect of temperature on respiration in yeast. 5 cm 3 of yeast suspension was placed into a test tube with 1 cm 3 of triphenyl tetrazolium chloride (TTC). TTC is an artificial hydrogen acceptor which is colourless when oxidised but turns red when reduced. Both solutions were equilibrated at each temperature prior to mixing and the experiment carried out three times at each temperature. The results are shown in the graph below: a) The student concluded the optimum temperature for respiration in the yeast was 45°C. Evaluate this statement. (3) ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... b) Explain two ways in which the experiment could be improved to increase reliability of the data. (2) ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... mean time taken for colour to change /s The e ect of temperature on respiration in yeast temperature /°C 50 100 150 200 250 0 35 40 45 50 55 16 | WJEC Biology for A2 Level: Revision Workbook | Unit 3 Energy, Homeostasis and the Environment Copyright: Sample material