Question

Cell wall.....??????? ​

Answer 1

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What is Cell Wall?

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$\textbf{Cell Wall:}$ It is the most outer covering of some cells like plant cell, bacteria, fungi etc.

◾ It is a non living and rigid structure.

$\textbf{\underline{Composition of cell wall :}}$

◾ $\textbf{Plant cell wall :}$

It is made up of cellulose, hemi-cellulose, pectines and protein.

◾$\textbf{Algae cell wall :}$

It is made up of cellulose, galactans, mannans and minerals like calcium carbonate.

◾$\textbf{Fungi cell wall :}$

It is made up of Chitin [also known as fungal cellulose, it is a polymer of N-acetyl Glucosamine Unit (NAG)].

$\textbf{\underline{Structure of Cell Wall : }}$

It is made up of two layers :

◾ Primary Cell Wall

It is the first produced cell wall, inner to middle lamellae. It gradually diminishes as the cell attains maturity.

◾ Secondary Cell Wall

It is formed inner the primary cell wall due to deposition of internal matter of cell. It is usually 3-layered.

Answer 2

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$\huge\red\star$ Cell Wall $\huge\red \star$

It is outermost rigid, freely permeable layer found outside the plasma membrane in all the plant cells, bacteria, blue-green algae, some protist and all fungi. It is absent from the animal cells.

★ Structure & function :-

Cell Wall of plant cells isn't formed of a fibrous polysaccharide called cellulose, while it is formed of Peptidoglycan in bacteria & blue-green algal cells but in formed of citin in most of fungi. Cell Wall is protective & supportive coat. It also provides a definite shape to the cell. It is freely permeable to many substances. It exerts an inward wall pressure to resist the outward - directed turgor pressure exerted by cell sap so the plant cells can withstand much greater changes in the surrounding medium than animals cells.