Carbohydrates exam q

Question 1

Use of a colorimeter in this investigation would improve the repeatability of the student’s results. suggest how

Answer 1

Quantitative
OR
(Colour change is) subjective;
Standardises (the) method;

Question 2

Glycogen and cellulose are both carbohydrates.
Describe two differences between the structure of a cellulose molecule and a glycogen molecule.

Answer 2

• Cellulose is made up of β-glucose (monomers) and glycogen is made up of α-glucose (monomers);
• glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4- glycosidic bonds;

Question 3

Describe the structure of glycogen

Answer 3

Polysaccharide of α-glucose;
(Joined by) glycosidic bonds
or
Branched structure;

Question 4

Suggest how glycogen acts as a source of energy

Answer 4

Hydrolysed (to glucose);
Glucose used in respiration;

Question 5

Explain the difference in the structure of the starch molecule and the cellulose molecule (2)

Answer 5

1. Starch formed from α-glucose but cellulose formed from β-glucose;
2. Position of hydrogen and hydroxyl groups on carbon atom 1 inverted.

Question 6

Explain how cellulose molecules are adapted for their function in plant cells (3)

Answer 6

1. Long and straight chains;
2. Become linked together by many hydrogen bonds to form
   fibrils;
3. Provide strength (to cell wall).