Starch & Glycogen: Structures & Functions

Question 1

Polysaccharides are

Answer 1

insoluble macromolecules that are polymers formed by many monosaccharides joined by glycosidic bonds in a condensation reaction to form chains.

Question 1

Starch and glycogen are

Answer 1

polysaccharides

Question 2

Polysaccharides chains can be

Answer 2

Branched or unbranched

Folded (making the molecule compact which is ideal for storage eg. starch and glycogen)

Straight (making the molecules suitable to construct cellular structures e.g. cellulose) or coiled

Question 3

Starch and glycogen are storage polysaccharides because they are

Answer 3

Compact/coiled (so large quantities can be stored)

Insoluble (so will have no osmotic effect, unlike glucose which would lower the water potential of a cell causing water to move into cells, cells would then have to have thicker cell walls - plants or burst if they were animal cells)

Question 4

Starch is the

Answer 4

storage polysaccharide of plants. It is stored as granules in plastids

Question 5

Due to the many monomers in a starch molecule, it takes longer to

Answer 5

Due to the many monomers in a starch molecule, it takes longer to digest than glucose

Question 6

Starch is constructed from two different polysaccharides:

Answer 6

Amylose (10 - 30% of starch)

Unbranched helix-shaped chain with 1,4 glycosidic bonds between α-glucose molecules

The helix shape enables it to be more compact and thus it is more resistant to digestion

Question 7

the branched form of starch has many ends why is this

Answer 7

1,4 glycosidic bonds between α-glucose molecules but also 1,6 glycosidic bonds form between glucose molecules creating a branched molecule

Can be acted on by enzymes simultaneously meaning glucose monomers are released rapidly

Question 8

Glycogen is the storage polysaccharide because of it is

Answer 8

it is highly branched and coiled

Question 9

What human body parts have a high concentration glycogen

Answer 9

Liver and muscles cells have a high concentration of glycogen, present as visible granules, as the cellular respiration rate is high in these cells (due to animals being mobile)

Question 10

how does glycogen branching help

Answer 10

Glycogen is more branched than amylopectin making it more compact which helps animals store more

The branching enables more free ends where glucose molecules can either be added or removed allowing for condensation and hydrolysis reactions to occur more rapidly – thus the storage or release of glucose can suit the demands of the cell

has more ends enzymes can simultaneously therefore it is rapidly broken down into glucose monomers which are used in respiration

this is more important for animals to have a high metabolic rate and therefore respiratory due to them being more active

Question 11

What does starch form when it is hydrolysed and why this this good

Answer 11

forms alpha glucose which is easily transported and readily in respiration