Lecture Seven : Cell walls and their role in regulating plant cell shape
5 important questions on Lecture Seven : Cell walls and their role in regulating plant cell shape
What is the structure of a primary plant cell wall ?
- Phase 1 : Crystalline Phase
- Cellulose fibres forms microfibrils that lines and forms the cell wall
- Phase 2 : Non-crystalline Phase - matrix in which the microfibrils are embedded
- Pectin polysaccharide
- Extensin network; proteins that crosslink pectin and cellulose
What are the functions of a primary plant cell wall ?
- Influences cell morphology
- Provides structural support
- Prevents excessive water uptake
Explain the synthesis of a primary plant cell wall ?
- Cellulose microfibrils: by rosette (cellulose synthase complex) at plasma membrane, Rosettes move parallel to cortical microtubules as they force out cellulose chains into cell wall.
- Hemicellulose and pectin: Synthesised & modified in the endomembrane system (Golgi apparatus), sent to wall in vesicles.
- Extensins: by rough ER.
- Formation of the middle lamella (a pectin layer which cements the cell walls of two adjoining plant cells together)
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What is the structure and function of a secondary plant cell wall ?
- Not all plant cells have this (water transporting cells)
- Synthesized into multiple layers, only after cell growth has stopped
- Thicker and stronger than primary cell walls
- Chemical make up:
- Contains more cellulose microfibrils
- less pectin
- Lignin : complex polymer that repels water, gives extra rigidity
What is a plasmodesmata and its function ?
- Allows cell to cell communication
- Allows free exchange of small molecules and movement of small organelles
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