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Date November 2019 Marks available 1 Reference code 19N.3.sl.TZ0.8
Level SL Paper 3 Time zone TZ0
Command term State Question number 8 Adapted from N/A

Question

Enzymes are biological catalysts.

The graph shows the relationship between the temperature and the rate of an enzyme-catalysed reaction.

State one reason for the decrease in rate above the optimum temperature.

[1]
a.

Explain why a change in pH affects the tertiary structure of an enzyme in solution.

[2]
b.

State one use of enzymes in reducing environmental problems.

[1]
c.

Markscheme

enzyme denatures
OR
change of conformation/shape of active site
OR
substrate cannot bind to active site/binds less efficiently ✔

NOTE: Accept “change in structure” or “substrate doesn't fit/fits poorly into active site”

a.

Any two of:
acidic/basic/ionizable/COOH/carboxyl/NH2/amino groups in the R groups/side chains «react» ✔
exchange/lose/gain protons/H+
change in H-bonds/ionic interactions/intermolecular forces/London dispersion forces ✔


NOTE: Do not accept “enzyme denatures” OR “change of conformation/tertiary structure” OR “substrate cannot bind to active site/binds less efficiently” as this was the answer to 8(a).

b.

breakdown of oil spills/industrial/sewage waste/plastics
OR
production of alternate sources of energy «such as bio diesel»
OR
involve less toxic chemical pathway «in industry» ✔

NOTE: Accept “«enzymes in» biological detergents can improve energy efficiency”.

c.

Examiners report

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

Syllabus sections

Options » B: Biochemistry » B.6 Biochemistry and the environment
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Options » B: Biochemistry
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Nature of Science

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