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Passive Transport

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Passive Transport

Postby Mr.Smoke » Fri Jan 20, 2006 11:52 am

Dear Friends,
what is passive transport in cell and how they work.
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Postby victor » Fri Jan 20, 2006 1:12 pm

Passive transport : transport 'something' done by cells without consuming ATP.
How they work? ahh...come on man..there're so many things to write then....
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Postby bearhug » Fri Jan 20, 2006 4:02 pm

Just think of as if you were swimming down a stream. It would be passive transport because it does not take much energy for you to go down with current. Facilitated diffusion is a form of passive transport, when something hydrophilic needs to go down a concentration gradient in a phospholipid bilayer it uses a transport protein to help it, since inside the bilayer is hydrophobic. This is like you using a kayak to go down a stream. Active transport would be like you trying to swim against the current.
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Postby Mr.Smoke » Fri Jan 20, 2006 4:59 pm

thanks
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Postby sdekivit » Fri Jan 20, 2006 6:37 pm

passive transport is transport down a concentration - or electrochemical gradient.
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Postby Mr.Smoke » Sat Jan 21, 2006 12:52 pm

ya offcourse! passive transport is the transportation of electrolyte present in cell, from higher to lower concentration and it do no need any energy..... but i wants to know its example and mechanism
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Postby victor » Sat Jan 21, 2006 1:17 pm

Example: diffusion of water molecule into the cell inside a hypotonic solution (that's the most simple one..:lol:)
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Postby victor » Sat Jan 21, 2006 1:17 pm

Example: diffusion of water molecule into the cell inside a hypotonic solution (that's the most simple one..:lol:)
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Postby Enzyme » Sat Jan 21, 2006 2:38 pm

The passive transport is a process of diffusion of molecules through the membrane. It is always produced in favour of gradient. Types of passive transport:

- Simple diffusion: Little molecules pass in favour of gradient but they can pass literally through the lipidic bilayer or by canal proteins. Examples: Transport of lipidic molecules (as steroidic hormones), anaesthetics as ether, liposoluble chemicals, apolar substances (as atmospheric oxygen and nitrogen) and some polar molecules (as carbon dioxide, ethanol, glycerin, etc). Also water pass by simple diffusion (it pass by canal proteins called aquoporines) by osmosis.

- Simple diffusion by regulated canal proteins: It is carried out by regulated canal proteins. Of this form, ions (as Na+, K+, Ca2+ and Cl-) come into the cell. Regulated canal proteins are proteins with a hole or internal canal which its opening is regulated by molecular signals (hormones, neurotransmissors, etc). The molecular signal joins to a certain region of the cell (its specific receptor) to activate the opening of the canal. When the molecular signal is joined with the receptor, the receptor suffers a structural change and the canal is opened.

- Facilitated diffusion: It allows the transport of little polar molecules as amino acids, monosaccharides, etc. As they can't pass through the lipidic bilayer, they require transmembranal proteins to pass into the cell. These transmembranal proteins are called permeases. When the molecule which is going to be transported joins to the permease, this protein suffers a conformational change and the molecule is pulled along into the cell.
Last edited by Enzyme on Sun Jan 22, 2006 3:43 pm, edited 1 time in total.
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Postby Enzyme » Sat Jan 21, 2006 2:44 pm

1. Simple diffusion (literally through the lipidic bilayer).
2. Simple diffusion (by canal proteins).
3. Facilitated diffusion.
4. Active transport.
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Postby Enzyme » Sat Jan 21, 2006 2:47 pm

Two diagrams about simple difussion by regulated canal proteins.
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Postby Mr.Smoke » Sat Jan 21, 2006 6:46 pm

Thanks Alot Enzyme
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