Starch, Cellulose and Plant Fibers

Starch

Starch is a polysaccharide carbohydrate in plants composed of numerous glucose atoms.
It serves as a vital energy reserve that is packaged into starch granules in plant cells.
There are two primary types of starch, amylose and amylopectin.
- Amylose is a straight chain of glucose units linked by alpha 1,4 glycosidic bonds.
- Amylopectin is a branched chain of glucose units with both alpha 1,4 and alpha 1,6 glycosidic bonds.

Cellulose is a major component of the cell wall in green plants.
It gives the plant rigidity and structural support, making it a principle source of fibre in the diet.
Structurally, cellulose comprises beta glucose molecules linked by 1,4 glycosidic bonds that results in a straight chain.
These cellulose chains line up to form microfibrils, which are held together by hydrogen bonds forming strong threads of cellulose fibres.

Plant fibres are made up of long chains of cellulose microfibrils. They provide plants with strength and flexibility.
These fibres find use in many commercial applications like the production of linen, cotton, and hemp.
They are grouped under two categories: seed fibres (e.g. cotton) and bast fibres (e.g. linen and hemp).
Seed fibres: These are derived from the seed or fruit part of the plant - for example, cotton fibres come from the cotton seed.
- Cotton is the purest form of cellulose and widely used in the textile industry.
Bast fibres: These are derived from the phloem or the inner bark (or skin) of the plant - e.g. flax for linen, jute and hemp.
- They have traditionally been used for rope, paper, or fabric due to their length, strength, and flexibility.