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Biology · Oct / Nov 2023 · Paper 42 · Question 4

0610

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The question as text

A scientist investigated the effect of temperature on the rate of photosynthesis in one species of plant. Photosynthesis involves enzyme-controlled reactions. Discs were cut from a leaf and kept at different temperatures. The total surface area of the discs was kept the same for each temperature. The volume of oxygen that was produced by the leaf discs was measured and used to estimate the rate of photosynthesis. The results are shown in Fig. 4.1. 10 20 25 30 35 40 temperature / °C rate of photosynthesis / arbitrary units 45 50 55 15 20 25 30 35 40 Fig. 4.1

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  • 4(a)[1]

    40 (°C) ;

  • 4(b)[6]

    any six from:

    before 40 °C

    1

    increasing temperature increases the kinetic energy (of

    reactants / molecules) ;

    2

    increasing the, frequency / rate, of (effective) collisions ;

    3

    more enzyme-substrate complexes are formed ;

    4

    releasing more, oxygen / glucose / products ;

    5

    temperature is the limiting factor ;

    at 40 °C

    6

    (optimum temperature) maximum number of, enzyme-substrate complexes / collisions;

    after 40 °C

    7

    increasing temperature changes the shape of active site(s) (of enzyme(s)) ;

    8

    ref. to denaturation ;

    9

    substrate, no longer complementary (to active sites) / can no longer fit into active sites ;

    10 fewer / no, enzyme-substrate complexes are formed ;

    11 fewer / no, products are released ;

    12 AVP ;

  • 4(c)[2]

    any two from:

    carbon dioxide is a limiting factor / so that carbon dioxide is not a limiting factor / AW ;

    so that temperature is the only, variable / limiting factor ;

    to ensure that the effects are caused (only) by temperature ;

  • 4(d)[1]

    any one from:

    (some is) used, for (aerobic) respiration / to react with glucose ; some remains in air spaces ;

  • 4(e)[2]

    any two from:

    absorbs / traps / captures, light ;

    transfers / converts, light energy into chemical energy ;

    for the synthesis of, glucose / carbohydrates ;

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