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Cell : The Unit of Life

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Describe cell wall.

The cell wall was first observed by Robert Hooke in 1665 in a thin slice of cork. Cell wall is a characteristics feature of prkaryotes (except mycoplasma) and plant cells. It is absent in animal cells. The cell wall is usually composed of cellulose. It may consist of other substances like lignin, pectin, hemi-cellulose etc. The cell wall has three layers called primary cell wall, secondary cell wall and middle lamellae. It determines the shape of the cell and provides structural support to the cell. 



 What are receptor molecules ?

Receptor molecules are specific proteins in the cell's plasma membrane that receive chemical signals from outside the cell. When such chemical signals bind to a receptor, they cause some form of cellular response. 

What is the function of contractile vacuole in amoeba?


Who concluded, “Cells are the ultimate units forming the structure of all plant tissues”?

Mathias Schleiden.

Who reported that the cell had an outer layer which is known as plasma membrane today?

Theodore Schwann 

State one difference between gram positive and gram negative bacteria.

Gram positive bacteria retains the gram stain whereas the Gram negative bacteria does not.