3.3 Summary Question & Exam Style Questions

Question 1

Describe the difference between alpha and beta glucose. [2]

Answer 1

Hydroxyl group on carbon 1 is in a different position (1); in alpha glucose it is below the ring in beta
glucose it is above the ring (1).

Question 2

Describe the formation of a glycosidic bond. [4]

Answer 2

Bond formed between two glucose molecules (1) – hydroxyl group of carbon 1 on one molecule
(1) and carbon 4 (1) on the other interact in a condensation reaction/removal of water molecule (1) to
form an ‘oxygen bridge’.

Question 3

Explain how the structure of cellulose is related to its function. [4]

Answer 3

Cellulose is straight chain molecule (1) with many hydrogen bonds between individual chains (1)
and staggered ends (1). This confers strength to the fibres (1).

Question 4

Explain why beta glucose, when polymerised, leads to the production of cellulose instead of starch. [6]

Answer 4

In beta glucose the hydroxyl group at carbon 1 is above the ring (1) so alternate glucose molecules
must rotate 180 degrees (1) so the hydroxyl groups on carbon 1 and carbon 4 are close enough to
react (1) condensation reaction (1) forming a glycosidic bond (1). The rotation of molecules produces
a straight chain molecule (1) – cellulose.