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Date November 2018 Marks available 1 Reference code 18N.3.sl.TZ0.8
Level SL Paper 3 Time zone TZ0
Command term Name Question number 8 Adapted from N/A

Question

Lactose, found in milk and dairy products, is a disaccharide formed from two different monosaccharides. The structure of lactose is shown with numbered carbon atoms.

Name the type of link between the two monosaccharide residues.

[1]
a.

Outline how the two monomer structures, galactose and glucose, differ.

[1]
b.

Markscheme

«1,4-»glycosidic ✔

 

Do not accept “glucosidic”.

a.

H and OH are reversed/in different positions on C-4 ✔

 

C-4 must be specified.

Do not penalize if reference is made to H and OH above and below ring/in alpha and beta positions on C-4 incorrectly.

b.

Examiners report

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

Syllabus sections

Options » B: Biochemistry » B.4 Carbohydrates
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