Biological Molecules - Sugars and Carbohydrates

Question 1

What is the general formula for carbohydrates?

Answer 1

1:2:1 - C:(H2):On

E.g if n = 3, formula = C3H6O3

Question 2

Define the term Monosaccharide?

Answer 2

Single sugar units.

Question 3

Why is glucose stored as glycogen?

Answer 3

• Glucose will dissolve, affecting the water potential of the cell,
• Glycogen is insoluble so doesn’t affect the water potential of the cell,
• Also, it is heavily branched so is more easily accessible so the surface area is larger, meaning the small branches can be accessed by more enzymes at the same time so glucose can be released faster.

Question 4

Give the properties of Glycogen?

Answer 4

• More heavily branched than amylopectin,
• Compact and insoluble,
• C1-4 bonds form chains with C1-6 side branches,
• Found mainly in the liver and muscles,
• Can have rapid hydrolysis and sugar release due to heavy branching (enzymes can access it more easily),

Question 5

Give the properties of Starch?

Answer 5

• Contains amylose and amylopectin,
• Made up of alpha glucose,
• Insoluble in water and so does not affect the water potential of cells,
• Stores glucose molecules in chains so that they can easily be ‘broken off’ and used in respiration.
• Is a storage molecule,

Question 6

Give the properties of Cellulose?

Answer 6

• Most abundant organic molecule on the planet,
• 50% of carbon in plants is tied up in cellulose,
• We can’t digest it,
• Very fibrous,
• Unbranched,
• Provides structure in plants,
• Consists of several thousand β glucose joined together in a long straight chain by B 1-4 glycosidic bonds,
• Every second molecule rotated by 180°
• Very tensile and strong.

Question 7

Give the properties of Amylose?

Answer 7

• Is a coiled, unbranched chain,
• Glycosidic C1-C4 bonds formed through a condensation reaction,
• Polymer of alpha glucose,

Question 8

Give the properties of Amylopectin?

Answer 8

• A branched chain polymer of alpha glucose,
• C1-4 bonds form chains with C1-6 side branches,
• Has more branches so more surface area so easier for enzymes to access it and break it down,

Question 9

Give the properties of Chitin?

Answer 9

• Polysaccharide,
• Makes up exoskeleton of insects,
• Chitin is very tough,
• The active monomer is glucosamine,
• Lightweight and waterproof,