"Protein icebergs in the sea of lipids" is the common statement used for the structure of the plasma membrane.
(a) explain the structure o plasma membrane with respect to this statement.
(b)explain the 2 important transport mechanisms taking place through the plasma membrane in living cells
(c)explain with reference to the laws of osmosis the fate of an animal cell and plant cell in hypotonic, hypertonic and isotonic solution.

(a) The basic structure of the plasma membrane was conceived by Singer and Nicolson in 1972 and is known as the fluid mosaic model. It is used for describing the structure of the plasma membrane. According to this model, the major components of the plasma membrane are lipids and proteins. A small amount of carbohydrates can also be found in it. . It consists of lipid bilayer (sea of lipids) in which intrinsic, extrinsic and transmembrane proteins (proteins ice bergs) are arranged. The plasma membrane is flexible in nature and allows the entry and exit of selective molecules.

(b) The two transport mechanisms are:

Passive transport − does not require energy. For example, neutral solute moves by diffusion, along the concentration gradient.
Water moves through osmosis.
Polar molecules that cannot diffuse move through facilitated diffusion, carried out by carrier proteins

 Active transport − requires energy for transport against the concentration gradient. For example, uptake of glucose in intestinal cells, minerals in root hair cells.

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