TYPES OF TRANSPORT MECHANISM

Transport mechanisms are described as four types:

1)Passive transport

2)Faciliated transport

3)Active transport

4)Bulk transport

PASSIVE  TRANSPORT OR DIFFUSSION:

§Simple diffusion :-

                                molecules are passing through membrane on their concentration gradient from higher to lower concentration due to their own kinetic energy.

§It does not require any metabolic energy.

§[solution = solute particle in less amount + solvent in higher amount],   when the solute particles arranged uniformly then solution is called homogenous solution.

§For eg : cells are having higher amount of  k+ ions instead of environment , so cells draw k+ ions from environment.

§Membrane of kidney cells , epithelial cells, red blood cells and muscles cells are impermeable to substance unless their transport is facilitated .All membranes are permeable for o2 , co2 , and water .

Diffusion down concentration gradient: 

Simple diffusion :In a concentration solution , a substance separated by its dilution , so the solute molecule move from higher to lower concentration until equilibrium is reached , it a physical phenomenon and its does not depends on cellular energy.

  Empirical term of diffusion can be explained by the first law of fick:             

                         dm/dt= - DA [dc/dx]

                                                       dm/dt= flow of matter in per moles

                                                      dc/dx = concentration gradient

                                                     D = diffusion gradient. [cm2 s-1]

Diffusion down the electrical gradient:                                        In a solution the solutes are dissociates into ions and having charge. Cell are also having charge particles inside and outside the media, cell membrane maintain their potential difference, this difference is measured by MICROELECTRODE.  Its range from 50mV to 100mV.  The ions which involved to form potential gradient are k+ and Na+ ions .

                              Each individual substance will diffuse independently of others as per gradient of its own concentration, diffusion pressure, or partial pressure.

OSMOSIS:  Diffusion of water from semi permeable membrane that occurs under the influence or osmotically active solution.

                     ^= RTc               c= molar concentration

                                                R= constant

                                                 T= temperature

                                                ^= osmotic pressure

                                                

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