Carbohydrates, Water & Lipids

Question 1

Explain two ways in which the structures of amylose and glycogen make them suitable for energy storage (2)

Answer 1

• compact: so large molecules can fit into a small volume
• insoluble: does not affect osmotic balance

Question 2

Explain how the dipolar nature of water is essential for living organisms (2)

Answer 2

• water can form hydrogen bonds
• hydrogen bonds hold water together as a liquid, so that it can move in mass flow systems

Question 3

Describe the structure of starch (5)

Answer 3

• alpha glucose
• glycosidic bonds
• amylose: 1-4 glycosidic bonds / coiled
• amylopectin: 1-4 & 1-6 glycosidic bonds / branched
• compact molecule

Question 4

Explain: catalyst (2)

Answer 4

• speeds up rate of reaction
• without being used up

Question 5

Explain: hydrolysis (2)

Answer 5

• reaction with water
• breaks glycosidic bonds

Question 6

Describe the structure of glycogen (3)

Answer 6

• many alpha-glucose monomers
• joined by glycosidic bonds
• with side branches present

Question 7

Distinguish between: monosaccharides and disaccharides (2)

Answer 7

• mono consists of one sugar unit, disac. consists of two
• disac. has glycosidic bonds, mono doesnt

Question 8

Distinguish between: amylose and amylopectin (2)

Answer 8

• amylose is unbranced , amylopectin is branched
• amylose is coiled , amylopectin is not

Question 9

Explain why a diet consisting of a high proportion of carbohydrates could lead to obesity (2)

Answer 9

• carbohydrates provide source of energy
• excess carbohydrates are converted to fats

Question 10

Describe the structure of glycogen and explain why it is a suitable molecule for storing energy (4)

Answer 10

• compact: more glucose in smaller space
• insoluble: no osmotic effect
• large molecule: doesn’t diffuse out of cell

Question 11

Explain why it may it be better to make packaging from starch rather than from oil-based products (2)

Answer 11

• starch is sustainable & biodegradable

Question 12

Compare the structure of a cellulose molecule with the structure of starch (4)

Answer 12

• both made of glucose
• starch made of alpha-glucose , cellulose made of beta-glucose
• both made of 1-4 glycosidic bonds
• starch is branched

Question 13

Describe two ways in which the structure of starch is related to its function (4)

Answer 13

• Large structure : no osmotic effect
• Compact : more stored in less space

Question 14

Describe one structural difference between amylose and glycogen (1)

Answer 14

• Amylose is coiled , glycogen is not.

Question 15

Give three roles of water in a plant other than for pollen tube growth. (3)

Answer 15

• acts as transport medium
• acts as a solvent
• photosynthesis