Glycogen + Cellulose

Question 1

Glucose storage molecule in animals … and plants ……

Answer 1

glucose storage molecule in plants : starch
glucose storage molecule in animals - glycogen

Question 2

what are the major stores of glycogen

Answer 2

liver and muscle cells

Question 3

what is glycogen

Answer 3

Glycogen is a polymer of alpha glucose

Question 4

describe the structure of the polysaccharide glycogen

Answer 4

Glycogen is a polymer of alpha glucose

Most of the alpha glucose molecules are joined by 1,4 glycosidic bonds

Glycogen also contains branches

The glycosidic bond is between carbon 1 of one of the alpha glucose molecules and carbon 6 of the other alpha glucose molecules.
This is called a 1,6 glycosidic bond

The glucose molecules at the branch points are joined by 1,6 glycosidic bonds.

Question 5

explain how the structure of glycogen relates to its function in cells

Answer 5

Glycogen is a heavily branched polymer.
Contains many branches
This makes glycogen a very compact molecule
So a lot of it can be stored in a small space

Glycogen has a lot of branches, meaning it has a lot of free ends
Means enzymes can convert glycogen back to glucose very quickly

has lots of branches (more than starch), so has more ends that can be acted on simultaneously by enzymes.
it is therefore more rapidly broken down to form glucose molecules, which are used in respiration (important to animals with higher metabolic rate + therefore respiratory rate than plants because they are more active)

Glycogen is insoluble in water (unlike glucose)
This means that glycogen does not draw water into cells by osmosis

insoluble - therefore doesnt affect water potential - so water is not drawn into cells by osmosis - means cell does not cell - makes it good for storage

Also because glycogen is a large molecule/insoluble it cannot diffuse out of a cell

Question 6

draw the structure of glycogen

Question 7

difference between glycogen and amylopectin

Answer 7

They seem to have a similar structure

Glycogen is more branched than amylopectin

Question 8

how is glycogen different to glucose

Answer 8

Glycogen is insoluble in water (unlike glucose)
This means that glycogen does not draw water into cells by osmosis

Also because glycogen is a large molecule it cannot diffuse out of a cell

Question 9

what do all these features make glycogen

Glycogen is a heavily branched polymer.
Contains many branches
This makes glycogen a very compact molecule

Glycogen has a large number of branches, This makes glycogen therefore have a lot of free ends.

This means that enzymes can convert glycogen back to glucose very rapidly
This is important as animals often have a high rate of respiration and the energy needs of animals can change rapidly e.g. animal may have to move quickly to escape from a predator
if this happened then the rate of respiration would increase and glycogen in animals muscles could be rapidly converted to glucose to be used in resp.

Glycogen is insoluble in water (unlike glucose)
This means that glycogen does not draw water into cells by osmosis

Also because glycogen is a large molecule it cannot diffuse out of a cell

Answer 9

all these features make glycogen an ideal glucose storage molecule in animal cells

Question 10

how is glycogen and starch formed

Answer 10

Glycogen and starch are formed by the condensation of α glucose.

Question 11

how is cellulose formed

Answer 11

Cellulose is formed by the condensation of β-glucose

Question 12

where is cellulose found

Answer 12

Cellulose is a major part of the cell wall found in plant cells

Question 13

what is cellulose a polymer of

Answer 13

cellulose is a polymer of beta glucose

Question 14

explain the potential problem of forming a polysaccharide of beta glucose molecules

Answer 14

If you want to form glycosidic bonds between carbons 1 and 4, the hydroxyl groups (of the glucose molecules) point in different directions

Question 15

What needs to be done to combat the problem of hydroxyl groups of beta glucose pointing in different directions to form a glycosidic bond

Answer 15

When a molecule of cellulose is formed, every second beta glucose molecule flips. Now we can form a glycosidic bond between carbons 1 and 4

Question 16

draw the structure of the polysaccharide cellulose

Answer 16

https://cdn.savemyexams.com/cdn-cgi/image/w=960,f=auto/uploads/2020/12/Cellulose_-hydrogen-bond-formation-between-chains.png

Question 17

state examples of polysaccharides

Answer 17

amylose
amylopectin
glycogen
cellulose

Question 18

is cellulose branched

Answer 18

cellulose is an unbranched polysaccharide

Question 19

polysaccharides are _____

Answer 19

polysaccharides are insoluble

Question 20

describe the structure of cellulose - function

Answer 20

cellulose forms a straight chain without any branches
this allows cellulose molecules to get close together

chains run parallel to each other - cross linked by hydrogen bonds which add collective strength

hydrogen bonds can now form between adjacent chains (see book) - BETWEEN hydroxyl groups
because a huge number of hydrogen bonds form, this makes cellulose really strong - provide structural support

the strength allows the cellulose cell wall to carry out its functions

the cellulose cell wall is also permeable to molecules e.g. water

under normal conditions plant cells contain a lot of water
as water moves in by osmosis, the plant cell contents push outwards against the cellulose cell wall.
The strength of the cellulose cell wall means that it can resist the outwards pressure due to the cell contents
this prevents the plant cell from bursting

the plant cell becomes rigid when it is full of water. this is called turgid.
the turgid plant cells hep to give the plant its upright structure

1 hydrogen bond weak
the combined effect of many hydrogen bonds iw q lo5
……………….

insoluble - therefore doesnt affect water potential - so water is not drawn into cells by osmosis - means cell does not cell - makes it good for storage

Question 21

what is it called when cellulose chains group together

Answer 21

when cellulose chains group together, it is called a microfibril

Question 22

what do microfibrils group together to form

Answer 22

microfibrils group together to form larger structures called macro-fibrils

Question 23

what do macro-fibrils group together to form

Answer 23

macro-fibrils group together to form a cellulose fibre

Question 24

what do cellulose fibres form

Answer 24

The cellulose fibres form the plant cell wall

Question 25

what happens when a plant cell is full of water

Answer 25

the plant cell becomes rigid when it is full of water. this is called turgid.

Question 26

cellulose is not a coiled chain like starch instead it has

Answer 26

cellulose is not a coiled chain like starch instead it has straight, unbranched chains

Question 27

how does the cellulose cell wall prevent the cell from bursting as water enters it by osmosis

Answer 27

the cellulose cell wall prevent the cell from bursting as water enters it by osmosis

it exerts an inward pressure that stops any further influx of water

as a result plant cells are turgid and push against one another

______________________
under normal conditions plant cells contain a lot of water
as water moves in by osmosis, the plant cell contents push outwards against the cellulose cell wall.
The strength of the cellulose cell wall means that it can resist the outwards pressure due to the cell contents
this prevents the plant cell from bursting

the plant cell becomes rigid when it is full of water. this is called turgid.
the turgid plant cells hep to give the plant its upright structure