- Chapter 2.2 Cellulose and plant cell walls
- Cellulose is found in plants and forms cell walls. It is tough, insoluble and fibrous. It is the most common polysaccharide.
- Cellulose is a homo-polysaccharide made from long chains of beta glucose bonded through a condensation reaction to form glycosidic bonds.
- Rather than spiralling like chains of alpha glucose, cellulose chains are straight and lie side by side. The hydrogen bonds stop it from spiralling and strengthen and stabilise the moleculse.
- When 60-70 cellulose chains bond together thy form microfibrils which bundle together into macrofibrils containing up to 400 microfibrils which are embedded in pectins (glue) to form plant cell walls.
- Structure of plant cell walls: Micro/macrofibrils are strong due to the glycosidic and hydrogen bonds. They are difficult to break down due to the glycosidic bonds between glucose molecules and some animals don't have an enzyme to catalyse the reaction. Microfibrils have crosslinks for extra strength.
- Function of plant cell walls: Plants do not have a rigid skeleton so each cell needs to have strength to support the whole plant. There is space between macrofibrils for water and ions to pass on their way into and out of the cell to make the cell fully permeable.