QUESTION 25 (3 marks)
Maltose is a disaccharide formed when two monomers of α-glucose are joined.
a) Identify whether α-glucose is an aldose or ketose monosaccharide.
[1 mark]
b) Distinguish between α-glucose and β-glucose.
[2 marks]
QCAA guide · typeset solution
QCAA sample response and mark allocation
25a) | Glucose is an aldose monosaccharide. | • identifies that glucose is an aldose monosaccharide [1 mark] |
25b) | α-glucose has its OH group attached on the opposite side of the carbon ring (trans) to the CH2OH group, while β- glucose has its OH group attached on the same side of the ring (cis) as the CH2OH group. | • identifies that α-glucose has its OH group and CH2OH group attached to opposite sides of ring (trans) for [1 mark] • identifies that β-glucose has its OH group and CH2OH group attached on the same side of the ring (cis) [1 mark] |
QCAA sample response and marking criteria reproduced from the official guide.
Compare your working with the guide above.