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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 different types of membranes.

There are three types of membranes :

1. Permeable membranes. These membranes allow diffusion of both solvent and solute molecules or ions through them e.g. cell wall. 

2. Impermeable membranes. These membranes prevent any substance to pass through it. 

3. Semipermeable membranes. These types of membranes allow diffusion of  certain substances through it while prevent the others to pass through it. e.g. cell membrane. 


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. 

 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. 

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

Mathias Schleiden.

What is the function of contractile vacuole in amoeba?