17 WJEC Biology AS Level - Marianne Izen - 2nd Edition

Question 1

Draw a diagram to show how maltose is formed

Answer 1

Question 2

Draw a diagram to show how maltose is hydrolysed

Answer 2

Question 3

Draw a table to summarise information about disaccharides

Answer 3

Question 4

Describe disaccharides

Answer 4

Disaccharides are composed of two monosaccharide units bonded together with the formation of a glycosidic bond and the elimination of water.

This is an example of a condensation reaction.

Question 5

What is the principle behind Benedict’s test?

Answer 5

Reducing sugars are sugars that can donate an electron.

The Benedict’s test detects reducing sugars in a solution.

The reducing sugar donates an electron to reduce copper(II) ions in copper sulphate solution, which is blue. The Cu(II) ions are reduced to Cu(I) ions in red copper (I) oxide.

Cu2+ (blue) + e- —> Cu+ (red)

Question 6

What are the rules when writing a chemical name?

Answer 6

When writing a chemical name, a word and a number are separated by a hyphen; numbers are separated by commas.

Question 7

What does the term reducing sugars include?

Answer 7

Reducing sugars include all monosaccharides and some disaccharides, e.g. maltose.