Glycogen + Cellulose Flashcards
Glucose storage molecule in animals … and plants ……
glucose storage molecule in plants : starch
glucose storage molecule in animals - glycogen
what are the major stores of glycogen
liver and muscle cells
what is glycogen
Glycogen is a polymer of alpha glucose
describe the structure of the polysaccharide glycogen
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.
explain how the structure of glycogen relates to its function in cells
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
draw the structure of glycogen
difference between glycogen and amylopectin
They seem to have a similar structure
Glycogen is more branched than amylopectin
how is glycogen different to glucose
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
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
all these features make glycogen an ideal glucose storage molecule in animal cells
how is glycogen and starch formed
Glycogen and starch are formed by the condensation of α glucose.
how is cellulose formed
Cellulose is formed by the condensation of β-glucose
where is cellulose found
Cellulose is a major part of the cell wall found in plant cells
what is cellulose a polymer of
cellulose is a polymer of beta glucose
explain the potential problem of forming a polysaccharide of beta glucose molecules
If you want to form glycosidic bonds between carbons 1 and 4, the hydroxyl groups (of the glucose molecules) point in different directions
What needs to be done to combat the problem of hydroxyl groups of beta glucose pointing in different directions to form a glycosidic bond
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
draw the structure of the polysaccharide cellulose
https://cdn.savemyexams.com/cdn-cgi/image/w=960,f=auto/uploads/2020/12/Cellulose_-hydrogen-bond-formation-between-chains.png
state examples of polysaccharides
amylose
amylopectin
glycogen
cellulose
is cellulose branched
cellulose is an unbranched polysaccharide
polysaccharides are _____
polysaccharides are insoluble
describe the structure of cellulose - function
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
what is it called when cellulose chains group together
when cellulose chains group together, it is called a microfibril
what do microfibrils group together to form
microfibrils group together to form larger structures called macro-fibrils
what do macro-fibrils group together to form
macro-fibrils group together to form a cellulose fibre
what do cellulose fibres form
The cellulose fibres form the plant cell wall
what happens when a plant cell is full of water
the plant cell becomes rigid when it is full of water. this is called turgid.
cellulose is not a coiled chain like starch instead it has
cellulose is not a coiled chain like starch instead it has straight, unbranched chains
how does the cellulose cell wall prevent the cell from bursting as water enters it by osmosis
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
