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Biology · May / June 2023 · Paper 61 · Question 1

0610

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The question as text

A student investigated the effect of temperature on the rate of respiration in yeast cells. When yeast cells respire they release carbon dioxide gas. The student used this method: Step 1 Fill a syringe with 15 cm3 of yeast suspension. Step 2 Gently lower the syringe into the measuring cylinder, as shown in Fig. 1.1. Step 3 Fill the measuring cylinder with hot water. Ensure that the water level in the measuring cylinder is above the syringe nozzle. measuring cylinder water bubble of carbon dioxide gas yeast suspension syringe nozzle Fig. 1.1 Step 4 Measure the temperature of the water in the measuring cylinder. Step 5 Start the stop-clock and wait for two minutes. Step 6 After two minutes, reset the stop-clock to zero. Step 7 Start the stop-clock again and count the number of bubbles produced by the yeast suspension in three minutes. Step 8 Pour the hot water in the measuring cylinder into the waste container. The syringe containing the yeast suspension should remain in the measuring cylinder. Step 9 Fill the measuring cylinder with cold water. Ensure that the water level in the measuring cylinder is above the syringe nozzle. Step 10 Repeat steps 4 to 7. 4 Fig. 1.2 shows the thermometer during step 4 and step 10. hot water °C 0 10 20 30 40 50 cold water °C 0 10 20 30 40 50 Fig. 1.2 Fig. 1.3 shows the number of bubbles the student counted in three minutes in step 7 and step 10. hot water – 54 bubbles cold water – 12 bubbles Fig. 1.3

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  • 1(a)(i)[3]

    1 table drawn with minimum of two columns and a header line ;

    2 appropriate column / row headings in the correct positions, with units for temperature ;

    temperature °C and number of bubbles (in 3 minutes) 3 recording of two correct temperatures (42 and 18) and two correct numbers of bubbles (54 and 12) ;

  • 1(a)(ii)[1]

    the higher the temperature the greater the rate of respiration / ora ;

  • 1(a)(iii)[1]

    (hot) 18 (bubbles per minute) and (cold) 4 (bubbles per minute) ;

  • 1(a)(iv)[1]

    temperature ;

  • 1(a)(v)[2]

    any two from:

    volume of yeast ;

    concentration of yeast ;

    type / batch / sample, of yeast ;

    time for counting bubbles ;

    time for, equilibration / waiting / AW ;

    (total) time, yeast (suspension) / syringe, was in the water / for the experiment ;

  • 1(a)(vi)[1]

    to allow the temperature of the yeast to become the same as the water / idea of equilibration/AW;

  • 1(a)(vii)[1]

    bubbles are different, sizes / volumes / AW ;

    idea that easy to miscount ;

  • 1(b)[2]

    delivery tube drawn and labelled ;

    measuring cylinder inverted in water drawn and labelled ;

  • 1(c)[2]

    add Benedict’s (solution / reagent) ;

    heat / warm ;

  • 1(d)[6]

    independent variable:

    1

    different masses of, sodium chloride / salt ;

    detail of method:

    2

    using a, balance / scale, to measure mass of salt / (named) ingredients / dough ;

    3

    mixing / kneading ;

    4

    ref to measuring change in

    height / volume / circumference / size

    OR time taken to reach a set

    height / volume / circumference / size ;

    5

    method of measuring height / volume of dough ; 6, 7 and 8 variables kept constant, max 3 from ;;;

    same initial, volume / height / size / mass / amount, of dough
    type of flour / type of dough / batch of dough
    mass / amount, of flour
    type of yeast
    volume / amount / mass / concentration, of yeast
    volume / amount / mass, of water
    type of salt
    time, left to rise / of the reaction
    temperature
    diameter of container (for measuring height) 9 two or more repeats ;
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