2.4.1 CELL WALL

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About Cel l Wall

Objective

Plant cell encased by cell wal l

Cell Walls function

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CELL WALL

OBJECTIVES:

-Identify primary cell wall, middle lamella,

plasmodesmata and secondary cell wall

-Describe the function of cell wall

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ABOUT CELL WALL

The cell wall is one of the feature of plant

cells that distinguishes them from animal

cells.

Found in prokaryotes, fungi, plants and some

protists.

Situated out of plasma membrane and not one

of the component of protoplasm.

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Built by cellulose chain- where it is arrangedin long fibril structure.

Space between the fibril allows water, air and

soluble molecules pass through the wall

without any obstacle.

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A young plant cell first secretes relatively thin

and flexible wall called primary cell wall.

Between primary wall of adjacent cell is the

middle lamella, a thin layer rich in sticky

polysaccharides called pectin.

The middle lamella glues the cells together.

Plant cells are encased by cell

walls

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Cell wall

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Plant cell wall

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When the cell matures and stop growing, it

strengthens its wall.

Some plants cell do this simply by secretinghardening substance into the primary wall.

Other cell add a secondary cell wall betweenthe plasma membrane and the primary wall.

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The secondary wall, often deposited in

several laminated layers, has a strong anddurable matrix that affords the cell protectionand support.

Eg: Wood consist mainly of secondary wall

The cytoplasm of one cell is continuous with

the cytoplasm of its neighbours viaplasmodesmata, channel through the walls.

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Function Of Cell Wall

The strong wall of the cells holds the

plants to make it turgid

Maintains the shape of the cells

Prevent excessive water

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Function Of Cell Wall

The sticky middle lamella cements the

cell together.

Plasmodesmata enables trasportation in

between cells.

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Cell Wall vs. Membrane Cell

Features Membrane cell Cell WallIllustration Animal cell Plant cell

Structure

Position

In side the cell Outside of the

cell

Content 2 molecules of

lipid between 2

protein layers

Cellulose fiber

embedded in a

polysaccharide

matrix andprotein

See animal cell and plant cell

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Features Membrane cell Cell Wall

Thickness

and

elasticity

Thin and

elastic

Thick and

pertinacious

Location Only at animal

and plant cell

Only in plant

cell

Permeability Selectivepermeable Permeable

Cell Wall vs. Membrane Cell

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Bacteria cell wal

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17/17Plant cell