VPB 112: General Veterinary Biochemistry (1+1)

Biological significance Passive transport

BIOLOGICAL SIGNIFICANCE

• Diffusion plays an important role in living cells. Some of the important examples are
• Absorption of glucose from the intestine into blood.
• Exchange of oxygen and carbon dioxide between air and blood.
• Exchange of anions like chloride (Cl^-) for bicarbonate (HCO₃^-) in red blood cells.
• Conduction of nerve impulses depends on the passive diffusion of ions.
• Transport of a substance into a cell by facilitated diffusion is an example of uniport, in which there is a transport of only single molecule in one direction. For example: glucose is transported into erythrocytes by a uniport mechanism.
• When two substances are co-transported from one side of the membrane to the other such as sodium and amino acid and sodium and glucose, the process is called symport.
• When the transport of a substance in one direction is coupled to the transport of another substance in the opposite direction the process is called antiport. For example: the transport of Cl^- and HCO₃^-.
• Another important passive transport system is gated pores or channels. These transport system is for specific ions and small molecules.( pore is used for bacteria and channel is used for animals) These gates or channels open and close on receipt of a signal.