Transport through PLasma Membrane

• One of the most important functions of the plasma membrane is the transport of the molecules across it. The membrane is selectively permeable to some molecules present on either side of it. Many molecules can move briefly across the membrane without any requirement of energy and this is called the passive transport.
•  Neutral solutes may move across the membrane by the process of simple diffusion along the concentration gradient.i.e...from higher concentration to the lower Water may also move aCROSs this membrane from high to lower concentration Movement of water by diffusion is called osmosis.
• As the polar molecules(H2O) cannot pass through the nonpolar lipid bilayer, they require a carrier protein of the membrane to facilitate their transport across the membrane.
• A few ions or molecules are transported across the membrane against their concentration gradient, i.e., from lower to the higher concentration. Such a transport is an energy dependent process, in which ATP is utilised and is called active transport, e.g. Na /K Pump.

fig: Active and Passive transport of Plasma Membrane

(1) Endocytosis (Bulk transport) 

     (a) Pinocytosis or Cell Drinking - Ingestion of liquid material by plasmalemma in the form of vesicles or bag like structure (pinosome) is called pinocytosis.

     (b)Phagocytosis or Cell eating :- Ingestion of solid complex materials by membranes in the form of vesicles (Phagosome) is called Phagocytosis.

(2) Exocytosis/Endocytosis/Cell vomiting :- Egestion of waste materials from cell through plasma membrane.