Cell Wall: Study Notes

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Cell Wall

Cell wall is a nonliving outermost structure responsible for support and is secreted and maintained by the protoplasm.

In the young cell it is a thin and delicate but as the cell matures, the wall becomes thick due to the deposition of chemical substances on the inner surface.

Composition: Composed mainly of cellulose in plants, chitin in fungi, and peptidoglycan in bacteria.

Structure: Rigid and provides structural support to the cell, giving it shape and protecting it from external harm.

Function: Protects the cell, maintains its shape, and prevents excessive water uptake.

Occurrence: Found in plant cells, fungi, and most prokaryotic cells (bacteria), but absent in animal cells.

Middle Lamella:

• The first formed cell plate works as a cementing layer between two daughter cells and it is called middle lamella.
• It is a common layer between two cells and the two cells are separated when middle lamella is dissolved.
• It is composed of Calcium and Magnesium pectates.

Primary Wall:

• Bordering middle lamella, primary wall is the first product of cell, synthesis by protoplast.
• In young enlarging cells primary wall remains thin and elastic becoming thick and rigid with the approach of cell maturity.
• Primary cell wall contains hemi-cellulose upto 50%, cellulose upto 25% and smaller amount of pectin.
• Hemi-cellulose forms matrix of the wall in which cellulose microfibrils are embeded.

Secondary Wall:

• Secondary wall is formed by deposition of cellulose at the inside of primary wall.
• It mainly consists of cellulose or varying mixture of cellulose.
• Secondary wall may be modified through the deposition of lignin and other substances.

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