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Date May 2018 Marks available 3 Reference code 18M.2.HL.TZ2.4
Level Higher level Paper Paper 2 Time zone Time zone 2
Command term Explain Question number 4 Adapted from N/A

Question

The diagram shows alpha amylase.

Explain the secondary structure of this protein molecule.

[3]
a.

Amylase is used in human digestion.

State two sites of production of amylase.

[1]
b.i.

Amylase is used in human digestion.

State the function of amylase.

[1]
b.ii.

Explain how enzymes catalyse chemical reactions.

[3]
c.

Markscheme

a. secondary structure includes alpha helices/beta pleated sheets 

b. secondary structure «of this protein» consists «mainly» of alpha helices 

c. spiral coils «of polypeptide chain» held together by hydrogen bonds 

d. between oxygen «C=O» and hydrogen atoms «N−H» of amino acids«on backbone» 

e. «some» beta pleated sheets present in this protein

a.

salivary glands AND pancreas

Both needed.

b.i.

breaks down starch «by hydrolysis» into maltose/disaccharides

b.ii.

a. enzymes work by forming enzyme–substrate complexes 

b. binding of substrate«s» to active site «of enzyme» 

c. «enzyme» changes shape slightly
OR
puts strains on chemical bonds «of substrate» 

d. decreases activation energy / increases rate of reaction 

e. enzymes bind to specific substrates

Can show these points in an annotated diagram.

c.

Examiners report

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

Syllabus sections

Core » Topic 2: Molecular biology » 2.5 Enzymes
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