Wednesday, January 30, 2013

Membrane Transport and Osmotic Pressure

This is a good video giving an overview of all the different kinds of membrane transport.  It also includes an explanation of the sodium-potassium pump which is important in membrane potentials, and it would be great to watch this to help prepare for that section! :)



Overview of types of transport:

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Simple Diffusion
Dissolved stuff wants to get evenly spread out.
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Facilitated Diffusion
This shows all again, but notice the 2 in the middle:

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Osmosis
If the membrane isn't permeable to the solute (ions etc), water (the solvent) is what moves to try to get things evenly distributed.  This is called osmosis.
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Tonicity

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Due to the differences in tonicity, osmotic pressure can cause cells to change because the water moves trying to equalize the solute-solvent ratios.  Here is the classic example of red blood cells in plasma.  The hypertonic/ isotonic/ hypotonic is referring to the plasma or solution, in relation to the inside of the RBC.
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Primary Active Transport
Something is pumped against its concentration gradient, using ATP as the energy source
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Secondary Active Transport
Something is pumped against its concentration gradient, using something besides ATP as the energy source.  In these examples, one ion is pumped with its gradient, and that energy is used to pump something else against its gradient.  Here are a few examples:
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4 comments:

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  3. This is exactly what I was looking for. Thanks a bunch for sharing this.


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