Biology · May / June 2025 · Paper 42 · Question 6
0610
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The question as text
A scientist investigated the effect of changes in pH on the activity of two different protease enzymes. Each enzyme was placed in a hole in the centre of a jelly layer in a Petri dish. The jelly layer was made of protein. The investigation was carried out at a range of different pH values. After 60 minutes, the area of the jelly layer that had been broken down by enzyme L or enzyme M was recorded at each pH value tested. Fig. 6.1 is a diagram of the apparatus. hole in the middle of the jelly layer filled with a solution of enzyme L or enzyme M jelly layer made of protein Petri dish Fig. 6.1 Fig. 6.2 shows the results of the investigation. 0 1 2 3 4 5 6 7 8 9 pH 10 11 12 20 40 60 80 100 120 140 160 180 area of the jelly layer broken down / mm2 enzyme L enzyme M Key Fig. 6.2
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6(a)[5]
any five from:
1
enzyme activity reaches, peaks / increases and decreases (for L / M) ;
2
maximum (area digested) / peaks, is pH 2 for L and pH 10 for M ; 3
L has steepest increase in activity between pH 1 and 2 / M has most gradual increase from pH 3 to pH 10 / as pH increases / AW ; 4
L has higher activity than M at their optimum pHs / AW ; ora 5
L and M are active, between pH 3 and pH 5 ;
6
L has no activity, from / at pH 5 (and onwards) OR M has no activity, before / at, pH 3 ;
7
M is active for a wider pH range (in this investigation than L) ; ora 8
no change in activity between pH 7 and 8 for M ;
9
data quote with correct units that includes ref to pH and area where the enzyme is active ;
6(b)[3]
any three from:
no jelly is broken down / enzyme has no activity ;
enzyme / M / active site, is denatured ;
enzyme / M / active site, has changed shape ;
active site, does not fit / does not bind / is not complementary to, the substrate / protein in jelly ;
6(c)[2]
enzyme L: pepsin ;
location: stomach ;
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