Starch, Cellulose and Plant Fibers

Starch, Cellulose and Plant Fibers


  • 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

  • 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.