Question

Describe the functioning of ‘Particle Rosettes.’ What role does sucrose synthase play in their function?

Answer 1

Answer: Cellulose is one of the most abundant polysaccharides on earth.It is found in the cell walls of plants , bacteria, algae etc. It is a homopolymer of glucose having a linear chain of hundreds to thousands of d-glucose linked by beta 1,4 linkage.

In the formation of cellulose the separate glucan chains of thousand of glucose residues are made and then hydrogen bonded with each other to form a rigid structure,known as microfibrils.

Cellulose is synthesised by the enzyme complexes, which have synthase protein varients (isoforms) arranged in a unique fashion forming hexagonal,rosette shaped structure which is known as ‘particle rosette’. They are more than twenty in number.These particle rosettes synthesise the cellulose chains. Theses rosette structures are associated with the plasma membrane of the cell wall producing organisms.

The substrate required for action of cellulose synthase to produce cellulose is UDP-glucose (uridine diphosphate glucose). This UDP-glucose is produced from sucrose by the enzyme sucrose synthase. This enzyme is associated with the plasma membrane and it is a glycosyl transferase enzyme acting on sucrose.