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Date May 2018 Marks available 2 Reference code 18M.3.SL.TZ1.1
Level Standard level Paper Paper 3 Time zone Time zone 1
Command term Describe Question number 1 Adapted from N/A

Question

A study was carried out on the activity of catalase in bacteria living in extreme environments. Catalase decomposes hydrogen peroxide (H2O2). The data were obtained for a strain of bacteria called Vibrio rumoiensis which exhibits high catalase activity.

Describe the relationship between increasing H2O2 concentration and catalase activity.

[2]
a.

Identify two factors that would need to be controlled in generating these data.

[1]
b.

Evaluate the claim that, based on the data, the optimum H2O2 concentration for catalase is 70 mM.

[2]
c.

Markscheme

a. as H2O2 concentration increases catalase activity increases / positive correlation
(up to 70 mM) 

b. peak activity at approximately 70 mM 

c. activity decreases after the peak

a.

temperature / pH / enzyme concentration / enzyme volume / quantity of bacteria

2 answers for 1 mark.

b.

a. maximum peak / optimum around 70 mM 

b. but overlapping error bars around 70 mM 

c. no clear optimum / range between 60 − 90 mM 

d. may only be true for this strain Vibrio rumoiensis / other variables not reported (e.g. another form of catalase)

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Core » Topic 2: Molecular biology » 2.5 Enzymes
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