1.3 Carbohydrates — disaccharides and polysaccharides

Question 1

What are disaccharides?

Answer 1

Disaccharide is a sugar that is formed by combining two monosaccharides.

Question 2

How are disaccharides formed?

Answer 2

Condensation of two monosaccharides

Question 3

What will be formed when condensation reaction happens between two monosaccharides?

Answer 3

A glycosidic bond

Question 4

What are the examples of disaccharides?

Answer 4

1. maltose
2. sucrose
3. lactose

Question 5

How is maltose formed?

Answer 5

Condensation of two glucose molecules

Question 6

How is sucrose formed?

Answer 6

Condensation of a glucose molecules and a fructose molecule

Question 7

How is lactose formed?

Answer 7

Condensation of a glucose molecule and a galactose molecule

Question 8

What are polysaccharides?

Answer 8

Polysaccharides are polymers that are formed by combining many monosaccharides.

Question 9

How are polysaccharides formed?

Answer 9

Condensation of many monosaccharides/glucose units

Question 10

What will be formed when condensation reaction happens between many monosaccharides?

Answer 10

Glycosidic bonds

Question 11

What are the examples of polysaccharides?

Answer 11

1. starch
2. glycogen
3. cellulose

Question 12

Are polysaccharides soluble or insoluble? Why?

Answer 12

Insoluble, because they are very large molecules.

Question 13

How to test for non-reducing sugars?

Answer 13

1. heat the non-reducing sugar with dilute hydrochloric acid and neutralise it
2. the non-reducing sugar will turn into its monosaccharide components by hydrolysis
3. heat the solution with Benedict’s solution, if non-reducing sugar is present at start, the mixture will change from blue to red