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Diffusion

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Diffusion

Postby tiger-nap » Thu Sep 06, 2007 4:43 pm

I need to know the three factors which affect the process of diffusion.

So far, I understand that temperature does the whole kinetic energy thing, which gets particles really hyper so they spread faster through a solution or the atmosphere.


But can anyone help me with the other two?
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Postby mith » Thu Sep 06, 2007 4:57 pm

Here's a hint, just because you have energy doesn't mean that diffusion is going to go on forever...eventually it "stops". Why?
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Postby Darby » Fri Sep 07, 2007 3:10 am

And are you being asked about "regular" diffusion or diffusion through a membrane?
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Postby tiger-nap » Fri Sep 07, 2007 4:36 pm

Membrane.


Well. Energy runs out because...

oh dear.

The molecules will lose their energy after passing it on or using it up, right?
____ x o x ____
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Postby MrMistery » Fri Sep 07, 2007 7:37 pm

You can't use energy up - energy cannot be destroyed(first law of thermodynamics)

Google or wikipedia "electrochemical gradient"
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Postby mith » Fri Sep 07, 2007 8:49 pm

Let's say you're doing laundry. It's now the rinse cycle.

Your clothes are soapy.
The washer adds pure water.
Soap will diffuse into the water.

Now, why do you suppose additional rinse cycles might be used? Note that not all of the soap comes out, so you're not getting soapy water and clean laundry. You're getting soapy water and soapy laundry. You're getting an equilibrium.
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Postby MrMistery » Sat Sep 08, 2007 6:15 pm

you would make a very fun professor to have in class dave
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Postby MichaelXY » Sat Sep 08, 2007 11:44 pm

Are you saying I am wearing soapy clothes?

That explains this bubble on the front of my shirt. My wife kept saying it was a beer gut.
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Postby dr. dugmore » Mon Sep 10, 2007 8:57 am

MrMistery wrote:You can't use energy up - energy cannot be destroyed(first law of thermodynamics)

Google or wikipedia "electrochemical gradient"


comon! you knew wat he ment!

10/10 irrelevants points for you!
im disopointed in you....:(
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Postby MrMistery » Mon Sep 10, 2007 9:11 am

actually the important part of that post was the part with the electrochemical gradient.
Besides, I am allowed to post useless things. What are they gonna do, ban me? :D
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Postby blcr11 » Mon Sep 10, 2007 6:36 pm

So we’re talking simple diffusion of substances across a “standard” lipid bilayer, then. The factors, as I see them, would be temperature, concentration (or concentration gradient), and size. You could toss in solubility in lipids and/or charge, too. Temperature is sort of obvious—the higher the temperature, the faster the molecules move. Small molecules (especially lipophilic, small molecules) are more likely than larger molecules to move across a membrane by passive diffusion driven by a concentration gradient; also, the diffusion constant is inversely proportional to the square root of the molecular weight, so not only is it more difficult for them to enter the bilayer, but larger molecules just move more slowly than smaller ones do. Molecules in passive diffusion spontaneously move from areas of higher to areas of lower concentration until the concentrations in the two regions become equal and there is no longer any concentration gradient to drive the process. Because the interior of the bilayer is essentially hydrocarbon, charged molecules larger than a potassium ion are effectively barred from crossing the membrane passively. Larger charged or polar molecules almost always require some sort active or facilitated transport to get across.
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