B1 H - Sample set 1 Q8
8) Phenolphthalein is an indicator. It is pink in alkaline solutions and turns colourless as the pH decreases.
It can be used to measure the activity of the enzyme lipase on the breakdown of lipids.
Samples of milk containing phenolphthalein were incubated with lipase at different temperatures.
The time taken for the phenolphthalein to turn colourless was recorded and used to calculate the rate of enzyme activity.
Figure 10 shows these results.
It can be used to measure the activity of the enzyme lipase on the breakdown of lipids.
Samples of milk containing phenolphthalein were incubated with lipase at different temperatures.
The time taken for the phenolphthalein to turn colourless was recorded and used to calculate the rate of enzyme activity.
Figure 10 shows these results.
(a) (i) Explain why phenolphthalein turns colourless when lipase breaks down the lipids in milk. (2)
(ii) Describe the effect of temperature on the activity of lipase, as shown in Figure 10. (2)
(iii) Explain why the activity of lipase changes above a temperature of 40°C. (2)
(b) A student investigated the time taken for amylase to breakdown a 10% starch solution into glucose at 37°C. The student repeated the investigation five times.
Figure 11 shows the results.
(ii) Describe the effect of temperature on the activity of lipase, as shown in Figure 10. (2)
(iii) Explain why the activity of lipase changes above a temperature of 40°C. (2)
(b) A student investigated the time taken for amylase to breakdown a 10% starch solution into glucose at 37°C. The student repeated the investigation five times.
Figure 11 shows the results.
(i) Calculate the rate of amylase enzyme activity for the 10% starch solution. (3)
rate = ............................................................. s–1
The investigation was done at 37°C.
(ii) State one other variable that the student should have controlled during this investigation. (1)
(c) Different enzymes catalyse specific reactions. Explain why enzymes can only catalyse specific reactions. (2)
(Total for Question 8 = 12 marks)
(ii) State one other variable that the student should have controlled during this investigation. (1)
(c) Different enzymes catalyse specific reactions. Explain why enzymes can only catalyse specific reactions. (2)
(Total for Question 8 = 12 marks)