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Biology · Oct / Nov 2023 · Paper 62 · Question 1

0610

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The question as text

Students investigated the effect of temperature on the activity of amylase. Amylase is an enzyme that catalyses the breakdown of starch to form reducing sugars. The students used this method: Step 1 Use a pen to label a spotting tile as shown in Fig. 1.1. dimple 1 2 1 2 3 4 3 4 5 6 5 6 W C Fig. 1.1 Step 2 Put one drop of iodine solution into each of the dimples on the spotting tile. Step 3 Put 2 cm3 of 2% amylase solution into two test-tubes. Step 4 Label a third test-tube W and a fourth test-tube C. Step 5 Put 2 cm3 of starch suspension into test-tube W and into test-tube C. Step 6 Label a beaker W and put approximately 200 cm3 of warm water into beaker W. Step 7 Put test-tube W and one of the test-tubes containing 2 cm3 of 2% amylase solution into beaker W. Leave both test-tubes in beaker W for three minutes. Step 8 After three minutes, pour the 2% amylase solution into test-tube W and start the stop-clock. Step 9 Wait for 30 seconds and then use a pipette to remove a sample of the liquid from test-tube W. Put two drops of this sample into the dimple labelled W1 on the spotting tile. Record the colour of the liquid in dimple W1. Step 10 Repeat step 9 using dimple W2. Continue taking and testing samples of liquid from test-tube W at 30-second intervals, using the remaining dimples W3, W4, W5 and W6. Record the colour of the liquid in each dimple. Stop the stop-clock and reset it to zero. Step 11 Label a beaker C and put approximately 200 cm3 of cold water into beaker C. Step 12 Put test-tube C and the other test-tube containing 2 cm3 of 2% amylase solution into beaker C. Leave both test-tubes in beaker C for three minutes. Step 13 After three minutes, pour the 2% amylase solution into test-tube C and start the stop-clock. Step 14 Repeat step 9 and step 10 with test-tube C and the dimples labelled C1, C2, C3, C4, C5 3 The results of the investigation are shown in Fig. 1.2. 1 2 1 2 3 4 3 4 5 6 5 6 W C blue-black colour Key: yellow-brown colour Fig. 1.2

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Show the answer and mark scheme

  • 1(a)(i)[3]

    table drawn with minimum three columns and a header line ; appropriate column / row headings ;

    correct recording of 12, colours / results ;

  • 1(a)(ii)[1]

    the greater the temperature the greater the,

    enzyme / amylase, activity / AW / ora ;

  • 1(a)(iii)[1]

    temperature ;

  • 1(a)(iv)[3]

    any three from:

    (number of) drops of iodine (solution) ;

    volume of amylase / 2 cm3 amylase ;

    concentration of amylase ;

    same enzyme ;

    volume of starch (suspension) ;

    time for equilibration / AW ;

    sample intervals / time intervals ;

    number of drops of sample added to iodine (solution) ;

  • 1(b)(i)[1]

    any one from:

    idea that colour change might take place between sampling times ;

    time intervals were too long ;

    difficult to judge end point / colour change is subjective / it is qualitative ;

  • 1(b)(ii)[1]

    any one from:

    insulate the beaker / AW ;

    use a thermostatically controlled water-bath ;

    description of using a Bunsen burner and a thermometer to control the temperature ;

  • 1(b)(iii)[1]

    to equilibrate / to allow the temperature of the test tube contents to become the same as the water in the beaker / AW ;

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