Polysaccharides help

[Navin]

I have learnt in school about 3 polysaccharides: starch, glycogen and cellulose and know their structural formula.

I also fully understand how the structure of cellulose allows it to become a structural polysaccharide in plants.

However I do not understand some things. What is it that starch and glycogen have that make them storage polysaccharides?

Also, why is it that glycogen is the storage polysaccharide in animals/fungi whilst starch is the storage polysaccharide in plants and not vice-versa?

[victor]

that make them storage polysaccharides?? they ARE polysaccharides...a polymer of glucose.
for the second question, I can think that it's about the enzyme contained in each organisms..

[Navin]

I think you mistook what i said. When i say " storage polysaccharides" i mean polysaccharides whose function is for storage. Do you get it now?

So to further elaborate on my question: Why is starch used as for storage? Is it because of its structure? ...

[fran008]

The reason is because starch or glycogen in that matter are polymers of glucose/fructose- they have many units join together which they can hydrolyse to monomers and use them as energy. The energy store is the monomers themselves. They will be broken down to provide energy when needed.

[Navin]

Ok, then why is it that cellulose is not used for storage?

[MrMistery]

For the second question: less energy is spent to create/break down starch as oposed to glycogen, so plants use it. Animals, on the other hand use glycogen because it is much more easy to break down(the reaction is faster)- this is because of it's structure that has "branches"(didn't find a translation)

[Navin]

Thank you people, I understand it now. Oh yes it is ok to call it "branches". That is what my lecturer called them too.

[victor]

glycogen is composed of glucose polymer by forming alpha-1,4-glycosidic bond while cellulose is beta-1,4-glycosidic bond..this beta isoform have a stronger bonding so it would take lots of energy to breakdown those bonds...

[Navin]

1. Then since like mr.mistery said, that starch requires less energy to break than glycogen, does that mean that the alpha 1,6 glycosidic bond requires more energy to break than the alpha 1,4 glycosidic bond?

2.

on the other hand use glycogen because it is much more easy to break down(the reaction is faster)- this is because of it's structure that has "branches"(didn't find a translation) - MrMistery

How does having branches lead to that?