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The Cell Wall

The Cell Wall. The Cell Wall. Function. Protects the plant cell Maintains its shape Prevents excessive uptake of water Holds the plant up against the force of gravity Prokaryotes, fungi, and some protists also have cell walls. Chemical Composition. Thicker than plasma membrane

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The Cell Wall

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  1. The Cell Wall The Cell Wall

  2. Function • Protects the plant cell • Maintains its shape • Prevents excessive uptake of water • Holds the plant up against the force of gravity • Prokaryotes, fungi, and some protists also have cell walls

  3. Chemical Composition • Thicker than plasma membrane • Microfibrils • Made of polysaccharide cellulose • Synthesized by cellulose synthase (enzyme) • Secreted to the extracellular space • Embedded in a matrix of other polysaccharides & proteins

  4. Primary cell wall • Relatively thin & flexiblelayer • First secreted by a young cell

  5. Middle Lamella • Between primary walls of adjacent cells • Thin layer rich in sticky polysaccharides (pectins) • Glues adjacent cells together

  6. Secondary cell wall • Between the plasma membrane & primary wall • A strong and durable matrix often deposited in several laminated layers for cell protection & support

  7. Plasmodesmata • Channels between adjacent cells

  8. Plasmodesmata Central vacuole of cell Plasma membrane Secondary cell wall Primary cell wall Central vacuole of cell Middle lamella 1 µm Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata

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