A3. Polysaccharides

Question 1

How is the structure of cellulose suited to its function? (4 points)

Answer 1

Long, straight/unbranched chains of β glucose
Joined by hydrogen bonding
To form (micro/macro)fibrils;
Provides rigidity/strength

Question 2

Give 2 differences between the structure of cellulose and glycogen (4 things)

Answer 2

cellulose moleculesstraightchains; glycogen branched

cellulose beta glucose; glycogen alpha glucose

celluose molecules straight chains; glycogen coiled

celluose has only 1, 4 glycosidic bonds; glycogen has 1,4 and 1,6 bonds

Question 3

Describe and explain features of starch that makes it a good storage molecule (4 things)

Answer 3

Coiled/helical making it compact
Insoluble so does not affect the WP of cells
Large so cant cross the cell membrane
Branched so more ends for enzyme action

Question 4

What glycosidic bonds do amylose, amylopectin, glycogen and cellulose contain?

Answer 4

Amylose - 1-4 Alpha
Amylopectin - 1-4 and 1-6 Alpha
Glycogen - 1-4 and 1-6 Alpha
Cellulose - 1-4 beta

Question 5

How does the structure of glycogen make it suited to its function? (5 things)

Answer 5

It is insoluble so does not cause water to move into the cell via osmosis
It is large so does not diffuse out of animal cells
It is compact so more can be stored in a small space
It forms α-Glucose when hydrolysed for respiration
Many more branches than starch allow α-Glucose to be released faster from glycogen

Question 6

Amylose (4 things)

Answer 6

Long unbranched chains of a-glucose
Angle of glycosidic bonds give it coiled structure
Compact - therefore good for storage as you can fit a lot in a small space
Hydrogen bonds help hold structure

Question 7

Amylopectin (2 things)

Answer 7

Long branched chain of a-glucose

Branches mean there are many free end to allow enzymes to hydrolyse glycosidic bonds easily

Question 8

Test for Starch

Answer 8

• Add iodine in potassium iodide solution
• If positive = blue-black colour present