Question

How does transportation take place across the plasma membrane?

Answer 1

Plasma membrane:

1. The plasma membrane or cell membrane is a membrane composed of a lipid bilayer and proteins are embedded in this bilayer.
2. It is a selectively permeable membrane that allows the transportation of certain molecules or ions to pass through it.
3. The transportation of molecules across the plasma membrane takes place in two ways namely,

Active transport:

1. Active transport is the movement of molecules or ions across the plasma membrane by using cellular energy obtained from ATP.
2. It is the common method of salt absorption in plant cells.
3. It occurs against a concentration gradient and therefore it is also called an uphill transport.
4. The carrier protein molecules embedded in the membrane act as channels for the transportation of molecules into the cell.

Passive transport:

1. Passive transport is the movement of molecules or ions across the plasma membrane without using cellular energy. It occurs along the concentration gradient.
2. It is of two types namely, osmosis and diffusion.
3. Osmosis is the process by which water molecules pass from the region of higher concentration to the region of lower concentration by a selectively permeable membrane.
4. Diffusion is the process of spontaneous movement of molecules from the region of higher concentration to the region of lower concentration. It is an important process in which the exchange of gases in and out of the cell takes place.
5. Diffusion is divided into two types namely, simple diffusion and facilitated diffusion.
6. In simple diffusion, the transportation of molecules across the membrane takes place without the help of any transport proteins or carriers. During this process, the molecules pass through the phospholipid bilayer and dissolve into the aqueous solution on the opposite side.
7. Facilitated diffusion is the type of passive transport in which the molecules or ions pass across the plasma membrane with the help of transmembrane integral proteins. The plasma membrane consists of channels through which the movement of molecules or ions occurs.