Question

a. What is fluid mosaic model of cell membrane and what is its functional importance?

b. Describe the differences between active and passive transport of material across membrane with examples.

Answer 1

A. According to fluid mosaic model of plasma membrane given by Singer and Nicolson, the plasma membrane is fluid and mosaic in appearance.

It is fluid because the phospholipid present in the membrane are able to to rotate on their own axis and can also move from one location to the other. This movement is particularly important in the transportation of molecules across the surface of the cell through plasma membrane.

It is mosaic because of the random distribution of proteins, cholesterol and lipids.

Plasma membrane in the outermost covering of all the types of cells, prokaryotic and eukaryotic both. It is selectively permeable in nature because it controls the movement of molecules across the cell surface.

B.

	Passive transport	Active transport
Concentration gradient	along, high to low	against, low to high
Transport proteins	may or may not be required	always required
Energy by ATP hydrolysis	not required	required
Type of molecules transported	small polar, non polar, uncharged	large polar, charged
Example	diffusion of Oxygen and Carbon dioxide, Osmosis of water, facilitated diffusion of glucose via GLUT	Na+ pump, H+ pump

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