1.4 Starch, glycogen and cellulose

Question 1

where can starch be found?

give a common example.

Answer 1

many plants in the form of small granules or grains.

e.g chloroplasts

Question 2

why does osmosis not occur in starch and glycogen?

Answer 2

because they are insoluble

Question 3

what is the main role of starch?

Answer 3

energy storage

Question 4

name the five ways in which starch is suitable for its role.

Answer 4

insoluble
large molecule
compact
branched
hydrolysed form is an energy source

Question 5

when hydrolysed what does starch form?

why is this useful?

Answer 5

a-glucose, an energy source for respiration

Question 6

what effect does starch’s branched form have on its ability to break down?

Answer 6

many ends which can be acted on by enzymes which break down the chain into monosaccharides.

Question 7

what effect does being insoluble have on starch?

Answer 7

does not draw water into the cell

Question 8

where can starch be found?

In what form?

Answer 8

many parts of a plant in small grains.

Question 9

what is the importance of starch?

Answer 9

it forms a major energy source in most diets and is an important component of food.

Question 10

Are the chains branched or unbranched in starch?

Answer 10

can be both

Question 11

describe the two chains present in starch.

Answer 11

Amylose - a long unbranched chain of a-glucose with a coiled structure
Amylopectin - long branched chain of a-glucose

Question 12

what is cellulose a major component of ?

Answer 12

plant cell walls

Question 13

what effect does cellulose have on the cell wall of a plant?

Answer 13

provides rigidity to the cell wall.

stops the cell from bursting

Question 14

how does cellulose stop the plant cell from bursting?

Answer 14

it stops the cell wall from bursting by exerting an inward pressure that stops any influx of water

Question 15

how is cellulose made?

Answer 15

monomers of b-glucose

Question 16

In cellulose are the chains branched or unbranched?

Answer 16

unbranched and straight.

Question 17

describe the structure of cellulose.

Answer 17

straight unbranched chains run parallel to each other allowing hydrogen bonds to form cross-linkages between adjacent chains.

Question 18

what effect do the hydrogen bonds have on the cellulose molecule?

Answer 18

each hydrogen bond adds very little strength but the overall number of them makes the molecule very strong.

Question 19

how are cellulose molecules grouped together?

Answer 19

grouped together to form microfibrils, which in turn are arranged to form fibre groups.

Question 20

where and how is glycogen stored?

Answer 20

small granules in the muscles and liver

Question 21

to whom is glycogen the most important?

Answer 21

animals with a higher metabolic rate

Question 22

where can glycogen be found?

Answer 22

animal cells and bacteria

Question 23

what is the importance of glycogen?

Answer 23

major carbohydrate storage product of animals

Question 24

what does having ‘branches’ mean for glycogen?

Answer 24

enzymes can work quickly on the ends of the branches, this hydrolyses glucose molecules that can be used in respiration

Question 25

what is the main role of glycogen?

Answer 25

energy storage

Question 26

How is glycogen suitable for its role?

Answer 26

insoluble
compact
highly branched

Question 27

describe the effects of glycogen being insoluble.

Answer 27

does not draw water into the cell

does not diffuse of the cell

Question 28

Glycogen is compact, what does this mean?

Answer 28

a lot can be stored in a small place

Question 29

glycogen is highly branched, how does this help it break down?

Answer 29

being highly branched allows the ends to be worked on by enzymes allowing glycogen to be broken down into glucose monomers