Differences Between Diffusion and Osmosis PDF

Differences betlveei-, 1. 2. Diffusioncanoccur in any medium. The dif{using molecules may be solids, liquids 1..1i::-r. ' It occur. ,-:' '. -.- -..- 2" It inr-oir €i r' ,' : rr- = , '.--- -j:t,L:'t, :. -,1.,'. i-tt molecules only or gases. E 3. Semipermeai',= :- irr'.-'r,':r-u is required. 3. Semipe...

Differences betlveei-, 1. 2. Diffusioncanoccur in any medium. The dif{using molecules may be solids, liquids 1..1i::-r. ' It occur. ,-:' '. -.- -..- 2" It inr-oir €i r' ,' : rr- = , '.--- -j:t,L:'t, :. -,1.,'. i-tt molecules only or gases. E 3. Semipermeai',= :- irr'.-'r,':r-u is required. 3. Semipermeable membrane is not required. 4. It is dependent upon the free energy of 4, Though it is tl-re i1,.-1.1,-t't'. -':.rr,r'ent molecules only, yet influenceci 'ci- lr'.: :r'iitlr.e of other substances the molecules of diffusing substance only ; (solutes) itr the sr.ster:, presence of other substances in the system is of no importance. 5. An equilibrium in the free energy of 5. Equilibrium in the free energv of solvent molecules diffusion molecules is achieved in the is never achieved. system. l*+lir*rtl'r"i: 'If * r$,i:.** i. We have seen that the cely'plasma membrane acts as an effective barrier to the free diffusion of most molecuies of biological significance. Yet, it is essential that some materials enter and leave the cell. Nutrients such as sugars and materials of growth such as amino acids must enter the cell, anci the wastes of metabolism must be thrown out. Such molecules are lnoved across the membrane by special proteins called transport proteins or permeases. Permeases form a small passageway through the membrane, enabling the solute molecule to cross the phospholipid bilayer. Permeases are usually quite specific, only a limited group of chemical susbstances or perhaps even a single substance they recognise and transport. !.'r ,. { ' j t'.. ;! It is of following two tvpes: (1) Facilitated fransport/diffusion. In this case, the permease assists a molecule to di{fuse through the membrane that it cannot otherwise penetrate. (2\ Active transport. In this case, the energy is supplied to the slrstem (cailed pump) to transport molecules in a direction opposite to a concentration gradient. Faciiitated diffusion, therefore, differs from active transport in that it promotes movement in a downhill direction (i.e., in the direction of concentration gradient) onh,' and requires no metaboiic energy to drive the transport system. In many animals, facilitated transport (or facilitated diffusion) aids in the transport of glucose (b1ood sugar) into the body cells that oxidises it to get ATPs. The concentration of. glucose is greater in the b1ooc1 tl-Lan in the cells that consume it, favouring inward diffusion. Giucose is a u'ater solr-rl.1e molecr:ie that Lrr itself is unable to penetrate the membrane rapidly enough tc support the me:.-.:rrli.r'..,i ir'...tn\- celis. The carrier system (i.e., mediated transport) increases the irrrr arrl il.,rr r -.: - -. Ir. actir-e lransport -- r--.,c: :iru lrLr\-ec1 uphill against the forces of passive diffusion. Active lrai'.::.-:.:.-,...-s:- L..s.''.:.r'..-1rt,;.reof energv(frornATP)becausematerialsarepumpedagainst th"e c,,-:-:.:- : :.. - ,. ,:,=r'.: - l-re most important active transport system in all animals are those, that maintai:', -.-.. :.--,::: qr,.r.i.iettts between cells and the surrounding extracellular fluid or '|; "t,iiittttlcellsrequireahighinternalconcentrationof potassiuttlionsfortlrc external€rii-r r-':'. ,, :-. t"itd.for certain enzymatic ftLnctions. The potassium ion concentration protein sqntlrc:,: :. : -st.ie the cell than outside. Sodium ions, on the other hand, may be 10 may be 20 to 50 ti.me.. 24 n The Fundomentcl Unit of Life: Cell E