WJEC Biology for AS Level Student Book: 2nd Edition

Test yourself 1 A student investigated the action of the enzyme catalase. This enzyme catalyses the breakdown of hydrogen peroxide into oxygen and water. The student collected the oxygen given off, by displacement of water in a 10 cm 3 measuring cylinder. The volume of gas collected was recorded every 20 seconds as shown by the line labelled Y on Image 1.1. (a) The rate of reaction can be calculated using the formula: rate = time taken to collect volume of oxygen collected Use the formula to calculate the average rate in cm 3 minute –1 for the first 30 seconds. Give your answer to one decimal place. (2) (b) Describe one method of enhancing the accuracy of data gathered in this experiment. (1) (c) The initial rate is the rate of reaction at the start and is the maximum rate. It is shown by line X on Image 1.1. The initial rate is 19 cm 3 min –1 . Explain why the initial rate is greater than the rate calculated in (a). (2) (d) Image 1.2 shows the effect of temperature on the activity of an amylase enzyme found in bacteria that evolved and live in boiling water in volcanic regions. (i) Using the graph, describe and explain the effect of temperature on the rate of activity of the amylase. (6) (ii) Describe how the data collected could be made more reliable. (1) (iii) Suggest a difference that might be found between this bacterial amylase and an amylase found in humans, and explain why this difference might be advantageous to the bacteria. (2) (Total marks 14) 2 Five mung beans were placed on filter paper in each of six Petri dishes of 9 cm diameter and each dish was given 4 cm 3 of lead nitrate of different concentrations, measured with a 10 cm 3 syringe. The lengths of the roots were measured with a ruler after five days. The table below shows the mean root length of the mung bean seedlings at each lead nitrate concentration. Concentration of lead nitrate / mol dm –3 Mean length of root / mm 0 58 0.05 28 0.10 12 0.15 7 0.20 3 0.25 0 Image 1.1 Image 1.2 WJEC Biology for AS Level Fig ST16 0 20 40 60 80 100 120 140 Time/s Volume of oxygen/cm 3 0 1 2 3 4 5 6 7 8 9 10 X Y Fig ST17 20 40 60 80 100 120 140 Temperature/°C Rate of reaction/arbitrary units 0 50 10 92