Biology 2.2.4: Carbohydrates 2: Polysaccharides As Energy Stores

Question 1

what are polysaccharides?

Answer 1

polymers containing many monosaccharides linked by glycocidic bonds.

Question 2

what is the structure of amylose?

Answer 2

alpha 1-4 glycosidic bonds
found in plants
unbranched chains and helical structure
found in starch grains in chloroplasts
insoluble
has hydrogen bonds

Question 3

what is the structure of amylopectin?

Answer 3

alpha 1-4 and 1-6 glycosidic bonds
found in plants (starch grains in glucose)
branched chain, double helical structure
insoluble
has hydrogen bonds

Question 4

what is the structure of glycogen?

Answer 4

alpha 1-4 and 1-6 glycosidic bonds
found in animals (granules in cytoplasm)
branched chain
insoluble
no hydrogen bonds

Question 5

what is the structure of cellulose?

Answer 5

beta 1-4 glycosidic bonds
found in plants (cell wall)
unbranched chain
insoluble
has hydrogen bonds
glucose chains form rope-like microfibrils which layer to form a network

Question 6

what is chitin?

Answer 6

a polysaccharide in ekoskeletons of insecta and crustaceans, its monomers are similar to beta glucose and forms cross links between long parallel chains.

Question 7

why are polysaccharides a good energy store?

Answer 7

• glycogen and starch are compact so do not occupy large amounts of space
• polysaccharides hold glucose molecules in chains so they can easily be taken off by hydrolyisis
• polysaccharides are less soluble on water than monosaccharide so have no effect on water potential