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A Levels Biology (9700)•9700/13/M/J/19
Question 8 from 9700/13/M/J/19

Explanation

Hexose sugars in carbohydrates

Steps:

  • Identify the three hexose sugars from the diagram: typically 1 as α-D-glucose, 2 as β-D-glucose, 3 as β-D-fructose.
  • Recall sucrose is a disaccharide of α-D-glucose and β-D-fructose.
  • Note cellulose is a polymer of β-D-glucose.
  • Confirm amylose is a polymer of α-D-glucose; match each to option D's assignments.

Why D is correct:

  • D assigns sugar 3 (fructose) to sucrose, sugar 2 (β-glucose) to cellulose, and sugar 1 (α-glucose) to amylose, matching their structural monomers.

Why the others are wrong:

  • A mismatches cellulose with fructose (sugar 3), which is not a component.
  • B incorrectly links sucrose to only fructose (sugar 3), ignoring its glucose unit.
  • C swaps amylose and cellulose linkages, assigning α-glucose to cellulose.

Final answer: D

Topic: Carbohydrates and lipids

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