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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
How do neutral solutes move across the plasmalemma ? Can the polar molecules also move across it in the same way ? If not, then how are these transported across the membrane? 

The neutral solutes move across the plasma membrane by simple diffusion. They diffuse across the membrane along their concentration gradient that is from their higher concentration to their lower concentration.

Passage of polar molecules : Due to bilayer of nonpolar lipid molecules, the polar molecules cannot pass through biomembranes. They require carrier molecules to facilitate their transportation across membrane. The transport of certain molecules takes place against their concentraion gradient from lower to higher concentration, this process requires energy and is an active transport process. The energy is provided by ATP.

 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?


State one difference between gram positive and gram negative bacteria.

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

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