1.4 Starch,Glycogen and Cellulose Flashcards
What is the main role of starch
It is for energy storage it is suited for this because:
It is insoluble therefore it doesn’t affect water potential, so it is not drawn into cells by osmosis.
Being large and insoluble it also doesn’t diffuse out of cells
It is compact so it can be stored in small spaces
When hydrolysed it forms A- glucose which can both easily be transported and readily used in respiration
The branches form has many ends each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly.
What is the difference between Glycogen and Starch
Glycogen is found in animals and bacteria but never in plant cells.
Has a similar structure however glycogen has shorter chains and more branched
How is the glycogen structure suited for storage?
It is insoluble therefore it does not tend to draw water into the cell by osmosis
Insoluble so it does not diffuse out of cells
Compact so it can be stored in a small space
Highly branched than starch so it has more ends which can be acted on simultaneously by enzymes. Therefr it is more rapidly broken down to form glucose monomers, which can be used in respiration.
Why is glycogen better suited for animals rather than starch
Animals have a higher metabolic rate therefore so is the respiratory rate than plants as they are more active.
Glycogen is more branched, faster breakdown of alpha glucose
How is cellulose different from Starch and Glycogen
It is made of beta glucose. The means, rather than forming coiled compact chains, cellulose has straight unbranched chains.
These run parallel to one another allowing hydrogen bond to form cross linkages between adjacent chains.
While each individual hydrogen bond has little strength, in total it has a considerable contribution to strengthening cellulose.
How is cellulose suited to its function of providing support?
Made of b-glucose therefore it forms straight, unbranched chains.
Cellulose molecular chains run parallel to each other forming hydrogen bond which add collective strength
These molecules are grouped together to form microfibrils which in turn are grouped to form fibres which add yet more strength to cellulose
Where is Cellulose found
Cellulose is a major component of plant cel walls. It provides the riding to the plant cell.
The cellulose wall prevents the cell from bursting as water enters it by osmosis. It does this by exerting an inward pressure that st so any dither influx of water. As a result plant cells are turgid and push against one another making the plant semi rigidly
What can easily move in and out cells by facilitated diffusion ?
Alpha and beta cells
