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Date November 2019 Marks available 2 Reference code 19N.3.SL.TZ0.2
Level Standard level Paper Paper 3 Time zone TZ0 / no time zone
Command term Outline Question number 2 Adapted from N/A

Question

The enzyme beta-galactosidase hydrolyses lactose to release glucose and fructose. A study was carried out to determine how acidity affects the activity of a beta-galactosidase enzyme, extracted from the fungus Penicillium simplicissimum.

[Source: Cruz R, et al. Properties of a new fungal β-galactosidase with potential application in the dairy industry.
Revista de Microbiologia 30: 265–271, 1999]

State another independent variable that would affect the activity of this enzyme.

[1]
a.

Outline the measurements which would need to be taken to determine the activity of the beta-galactosidase at different pH values.

[2]
b.

Markscheme

temperature
OR
lactose/substrate concentration
OR
Inhibitors / cofactors ✔

Do not accept pH or acidity.

a.

a. test samples for the concentration/amount of products/glucose/fructose/substrate/lactose ✔ Accept use Benedict/Fehling to see change in amount of reducing sugar

b. take samples of the reaction mixture at regular/timed intervals ✔ Must indicate that samples are taken at timed intervals

c. repeated measurements «at the different pH values» ✔

d. measure independent/controlled/standardised/variables / temperature ✔

b.

Examiners report

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

Syllabus sections

Core » Topic 2: Molecular biology » 2.5 Enzymes
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