Starch, Cellulose And Glycogen

Question 1

Tell me about cellulose…

Answer 1

Is a polymer of beta glucose.
Condensation polymerisation occurs
The monomers are held by1,4 glycosidic bonds.
Alternate beta glucose molecules are inverted
The chain is long and straight
Adjacent chains can be held together by H-bonds

This forms micro-fibrils which are rigid and can link to form cellulose fibres
Cellulose is a component of the cell wall
Its strength means it can resist osmotic pressure

Question 2

Tell me all you know about Glycogen…

Answer 2

Glycogen is similar to amylopectin.

It is polymer of (1-4) alpha glucose with 9% (1-6) branches, though more than starch. Because it is so highly branched, it can be mobilised (broken down by glycogen phosphorylase to produce glucose for energy) very quickly, reflects the grater metabolic demands of animal over plant

Animal’s storage polysaccharide

Found mainly in muscle and liver.

Question 3

Tell me about the structure of starch…

Answer 3

Storage polysaccharide
Insoluble (no effect on water potential and thus osmotically inactive)
Not a pure substance but a mixture of

Amylose: a chain of alpha glucose held by 1,4 glycosidic bonds. It forms a helix, held by H bonds within the chain

Amylopectin: a polymer of alpha glucose with 1,4 glycosidic bonds and a small number of 1,6 branches. This gives it an open structure and the branches are quickly hydrolysed