Overview
This lecture explains the structure and function of cell walls in plants, algae, and fungi, focusing on composition, mechanical strength, and permeability.
Plant Cell Wall Structure and Function
- Plant cells are surrounded by a cell wall made of cellulose.
- The cell wall provides mechanical strength, helping plant cells resist outward hydrostatic pressure from water uptake.
- When plant cells are filled with water, the turgid cell wall supports the plant and prevents wilting.
- Loss of water reduces cell wall rigidity, causing plants to lose structure and wilt.
- The cell wall is permeable to water molecules, allowing water to enter and leave the cell.
- Cellulose is a polysaccharide formed from beta glucose monomers.
- Cellulose molecules form hydrogen bonds, creating strong microfibrils.
- Microfibrils build a mesh-like structure, giving the wall its strength.
- The middle lamella, located between plant cells, acts as a glue and is made of polysaccharides plus calcium and magnesium ions.
Algae and Fungi Cell Walls
- Algae cell walls contain cellulose and glycoproteins.
- Fungi cell walls are made of chitin, other polysaccharides, and glycoproteins.
- Both algae and fungi cell walls provide rigidity and define cell shape.
Key Terms & Definitions
- Cellulose — A polysaccharide consisting of beta glucose monomers, forming plant cell walls.
- Osmosis — The movement of water molecules through a membrane from high to low water potential.
- Hydrostatic Pressure — Pressure generated by water inside the cell pushing outward.
- Microfibril — A bundle of cellulose molecules linked by hydrogen bonds, strengthening the cell wall.
- Middle Lamella — A layer rich in polysaccharides and ions between plant cells, acting as an adhesive.
- Chitin — A polysaccharide forming the main component of fungal cell walls.
Action Items / Next Steps
- Review the structure and function of cellulose in the biological molecules topic.
- Learn key differences between plant, algae, and fungi cell walls for future lessons.