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Biology · May / June 2021 · Paper 62 · Question 1

0610

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The question as text

Catalase is an enzyme found in living cells. It catalyses the break-down of hydrogen peroxide to form water and oxygen. In this investigation a celery extract was used as a source of catalase. A student investigated the effect of catalase concentration on the rate of oxygen production. The student made five different concentrations of celery extract by diluting the celery extract by 5 Step 1 Five beakers were labelled A, B, C, D and E. Step 2 A 10 cm3 measuring cylinder was used to place 10 cm3 of celery extract into beaker A. Step 3 The same measuring cylinder was used to transfer 5 cm3 of celery extract from beaker A to beaker B. The same measuring cylinder was used to add 5 cm3 of distilled water to beaker B. Step 4 The same measuring cylinder was used to transfer 5 cm3 of celery extract from beaker B to beaker C. 5 cm3 of distilled water was added to beaker C. Step 5 The same measuring cylinder was used to transfer 5 cm3 of celery extract from beaker C to beaker D. 5 cm3 of distilled water was added to beaker D. Step 6 The same measuring cylinder was used to transfer 5 cm3 of celery extract from beaker D to beaker E. 5 cm3 of distilled water was added to beaker E.

Read automatically from the paper; the printed page above is exact.

Show the answer and mark scheme

  • 1(a)(i)[1]

    25.00

  • 1(a)(ii)[4]

    table drawn with minimum two columns and a header line ;

    appropriate column / row headings, with units ;

    recording of five concentrations / extracts and five times ;

    correct conversion of minutes to seconds ;

  • 1(a)(iii)[1]

    at higher concentrations (of catalase), the paper disc rises more quickly / oxygen production is higher / hydrogen peroxide breaks down to oxygen and water more quickly ;

  • 1(a)(iv)[2]

    independent – concentration (of catalase / celery extract) ;

    dependent – time (for paper disc to rise) ;

  • 1(b)(i)[2]

    height / distance (of hydrogen peroxide) ;

    divided by time taken ;

  • 1(b)(ii)[1]

    use of the same measuring cylinder / idea of contamination / mixture in the beaker was not stirred ;

  • 1(b)(iii)[1]

    any one from:

    soak the paper disc in, water OR boiled extract ;

    add a clean paper disc / disc with no catalase ;

  • 1(c)[6]

    independent variable:

    1

    at least 2 different concentrations of sodium chloride ;

    new method:

    2

    use of a, (gas) syringe / burette / measuring cylinder / balloon (to measure volume of oxygen) / counting bubbles ;

    3

    idea of, measuring (a volume of oxygen produced) in a set amount of time / measuring time to collect a set volume (of oxygen) ;

    given method:

    4

    soaking paper discs in, celery / catalase / AW ;

    5

    measuring time for disc to rise ;

    6 and 7 max 2 from variables kept constant ;;

    volume of sodium chloride (solution)
    temperature
    concentration / volume / amount, of hydrogen peroxide (solution)
    concentration / volume / amount, of catalase / celery

    (extract) / enzyme / catalyst

    pH / use of a buffer

    8

    use of a thermostatically controlled water-bath to control temperature ; 9

    repeat (experiment) two or more times ;

    10 suitable safety precaution ;

  • 1(d)[2]

    biuret (solution) ;

    purple ;

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