Biology · Oct / Nov 2022 · Paper 62 · Question 1
0610
As printed in the paper
The question as text
Some students investigated the effect of hydrogen peroxide concentration on the activity of catalase. Catalase is an enzyme found in yeast cells. The enzyme catalyses the breakdown of hydrogen peroxide to form water and oxygen. The reaction releases heat. The students compared the activity of catalase in two different concentrations of hydrogen peroxide solution by measuring the change in temperature during the reaction. The students used a yeast suspension as a source of catalase. The students used this method: Step 1 Aluminium foil was wrapped around the outside of a test-tube. The test-tube was labelled A. Step 2 Aluminium foil was wrapped around the outside of a second test-tube. This test-tube was labelled B. Step 3 A syringe was used to put 10 cm3 of hydrogen peroxide solution into test-tube A. Step 4 The temperature of the hydrogen peroxide solution in test-tube A was measured and recorded as 20 °C at 0 minutes. Step 5 The yeast suspension was stirred. 1 cm3 of yeast suspension was then added to the hydrogen peroxide solution in test-tube A and the stop-clock was started. Step 6 The temperature of the hydrogen peroxide solution in test-tube A was measured every minute for five minutes. The measurements from step 6 are shown in Fig. 1.1. 1 minute = 24°C 2 minutes = 28°C 3 minutes = 31°C 4 minutes = 33°C 5 minutes = 34°C Fig. 1.1 Step 7 A syringe was used to put 5 cm3 of hydrogen peroxide solution and 5 cm3 of distilled water into test-tube B. Step 8 Steps 4, 5 and 6 were repeated using test-tube B. These measurements are shown in Fig. 1.2. 1 minute = 24°C 0 minutes = 20°C 2 minutes = 26°C 3 minutes = 28°C 4 minutes = 29°C 5 minutes = 29°C Fig. 1.2
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Show the answer and mark scheme
1(a)(i)[3]
one table drawn with minimum three columns and a header line ; appropriate column / row headings, with units for both time and
temperature ;
recording of 12 correct temperatures ;
1(a)(ii)[2]
test-tube A: 14 (°C) ;
test-tube B: 9 (°C) ;
1(a)(iii)[1]
the, greater / higher, the concentration of hydrogen peroxide the greater the activity of catalase ;
1(a)(iv)[1]
temperature ;
1(b)(i)[2]
1
effect on the results if room temperature is lower:
the temperature change would be less / the temperature (in the test-tubes) would be lower / AW ;
2
explanation
(without the foil) there was, no insulation / (more) heat loss / AW ; OR
1
effect on the results if room temperature is higher:
temperature (in the test-tubes) would be higher ;
2
explanation
(without the foil) there was, no insulation / (more) heat gain / AW ;
1(b)(ii)[2]
any two from:
1
(total) volume of solution ;
2
volume / concentration / amount / type, of yeast ;
3
time (intervals at which measurements were taken) / total time for reaction ;
4
stirring of yeast ;
5
starting temperature (of solution) ;
1(c)(i)[2]
volume (of oxygen produced) ;
time (over which the oxygen is produced) ;
1(c)(ii)[1]
a result that does not fit the, pattern / trend / AW ;
1(c)(iii)[1]
they did not use the anomalous result in the calculation / AW ;
1(c)(iv)[4]
axes labelled with units ;
uses a linear scale and plotting area occupies half or more of the grid in both directions ;
all five points plotted accurately ± half a small square ;
suitable line drawn ;
1(c)(v)[2]
any two from:
the rate (of oxygen production / enzyme activity) increased then decreased as pH increased ;
peak at pH 8 / peak or plateau between pH 7–8 ;
use of data with units ;
1(c)(vi)[2]
test at smaller intervals of pH ;
between, pH 7–9 ;
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