Starch, glycogen and cellulose

Starch

Polysaccharide found in many parts of a plant in the form of small grains
made of a chain of a-glucose linked by glycosidic bonds formed during a condensation reaction
The main role of starch is energy storage

it is insoluble and therefore doesn't affect water potential, so water is not drawn into the cells by osmosis
being large and insoluble, it does not diffuse out of cells
it is compact, so a lot of it can be stored in a small space
when hydrolysed it forms a-glucose, which is both easily transported and readily used in respiration
the branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers arc released very rapidly.

found in animals and bacteria but never plants
similar structure to starch but shorter chains and more highly branched
major carbohydrate in animals
stored as small granules
- mainly in muscles and liver
The mass of carbohydrate that is stored is relatively small because fat is the main storage molecule in animals
Its structure suits it for storage because:
- it is insoluble and therefore docs not tend to draw water into the cells by osmosis
- being insoluble, it does not diffuse out of cells
- it is compact, so a lot of it can be stored in a small space
- It is more highly branched than starch and so has more ends that can be acted on simultaneously by enzymes. It is therefore more rapidly broken down to form glucose monomers, which are used in respiration.

Made of β-glucose
Forms straight unbranched chains
Cellulose chains run parallel to each other, forming hydrogen bonds which allow cross links
- many weak hydrogen bonds form a strong collective strength.
Cellulose molecules group to form microfibrils wich then are further grouped to form fibres, which provides more strength