Disaccharides

Question 1

What is a disaccharide

Answer 1

Two monosaccharides joined together by a glycoside bond.

Question 2

How are disaccharides formed

Answer 2

A disaccharide is formed when two monosaccharide units, create a glycosidic bond between each other, and the reaction releases water. (A condensation reaction)

Question 3

Between which carbon atoms does the glycosidic bond form in a dissacharide

Answer 3

• Between the carbon atom number 1 (C₁) of the alpha glucose molecule and carbon atom number 4 (C₄) of the other alpha glucose molecule
• This forms a C1 to C4 linkage

Question 4

What are the 3 types of disaccharide

Answer 4

Maltose Sucrose Lactose

Question 5

What are the components of the disaccharide sucrose

Answer 5

The monosaccharides glucose + fructose join together to form the disaccharide fructose

Question 6

What are the components of the disaccharide lactose

Answer 6

The monosaccharides glucose + galactose join together to form the disaccharide lactose

Question 7

What are the components of the dissacharide maltose

Answer 7

The monosaccharides glucose + glucose join together to form the disaccharide Maltose

Question 8

What is the biological role of maltose

Answer 8

Maltose is made up of two monosaccharides which are the same

Glucose + Glucose = Maltose

It is a malt sugar found in germinating seeds such as barley

Question 9

What is the biological role of sucrose

Answer 9

Sucrose has two different monosaccharides joined together by a glycosidic bond

Glucose + Fructose = Sucrose

Stored in plants such as sugar beat/cane and transported in the phloem of flowering plants

Question 10

What is the biological role of lactose

Answer 10

Lactose has two different monosaccharides joined together by a glycosidic bond

Glucose + Galactose = Lactose

Found in mamalian milk.

Question 11

What are the possible monosaccharide combinations of a dissacharide including an example…

Answer 11

• Two monosaccharides which are the same
  
  • Glucose + Glucose = Maltose
  • A malt sugar found in germinating seeds such as barley
• Two different monosaccharides joined together
  
  • Glucose + Galactose = Lactose
  • The main carbohydrate found in milk
• and
  
  • Glucose + Fructose = Sucrose
  • Stored in plants such as sugar beat/cane

Question 12

What is the name give to the process by which dissacharides are broken down into monosaccharides

Answer 12

Hydrolysis i.e. A water molecule is added

Question 13

3 points to bare in mind

Answer 13

• Dissacharides are still relatively small molecules
• They are water soluable
• They are more suitable for storage and transport than monosaccharides