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Date November 2018 Marks available 1 Reference code 18N.3.sl.TZ0.6
Level SL Paper 3 Time zone TZ0
Command term Outline Question number 6 Adapted from N/A

Question

Enzymes are mainly globular proteins.

Describe the interaction responsible for the secondary structure of a protein.

[2]
a.

Explain the action of an enzyme and state one of its limitations.

[3]
b.i.

Enzymes are widely used in washing detergents. Outline how they improve the efficiency of the process.

[1]
b.ii.

Markscheme

hydrogen bonding ✔

between C=O and H–N «groups» ✔

 

Accept a diagram which shows hydrogen bonding for M1 and which shows the interaction between O of C=O and H of NH groups for M2.

Accept “between amido/amide/carboxamide” but not “between amino/amine” for M2.

a.

Enzyme action:

Any two of:

substrate binds to active site ✔

weakens bonds in substrate ✔

 

lowers activation energy

OR

provides alternate pathway ✔

 

increases rate of reaction

OR

acts as catalyst ✔

 

substrate specific ✔

 

Limitation:

Any one of:

temperature dependent ✔

pH dependent ✔

can be sensitive to heavy metal ions ✔

sensitive to denaturation ✔

can be inhibited ✔

substrate specific ✔

 

Accept “favourable orientation/conformation of the substrate «enforced by enzyme»” for M1.

Do not accept “substrate specific” as both an enzyme action and a limitation.

b.i.

Any one of:

«increase rate of» hydrolyse/break down lipids/oils/fats/proteins ✔

«wash at» lower temperature/consume less energy ✔

b.ii.

Examiners report

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

Syllabus sections

Options » B: Biochemistry » B.6 Biochemistry and the environment
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