Cellular membrane and ions...

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Byrne
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Cellular membrane and ions...

Post by Byrne » Sun Apr 09, 2006 6:44 pm

Okay, I am in the process of completing a lab on the cell membrane and one of the discussion questions asks:

Can you name a few ions that must routinely move across the cell membrane?

I know Na+, K+, H+, Ca2+, Cl-, HCO3- ions all routinely move across the cell membrane...

but, the next question asks...

How long would your list eventually be?

I have no idea what this means. I think it's asking if there are a lot more ions that pass the cell membrane or if there are not any more that I mentioned. Do all types of ions pass the cell membrane? Or does the list pretty much end after the ones I mentioned.

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mith
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Post by mith » Mon Apr 10, 2006 2:40 am

I think it's trying to make you realized that selective permeablity means there's a limit and not everything will go through :D
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Enzyme
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Post by Enzyme » Mon Apr 10, 2006 8:24 am

mithrilhack is in the right way ;). Your second question makes reference to a very important characteristic of cell membrane: SELECTIVE PERMEABILITY.

Cell membrane controls the entrance and exit of all the materials which want to pass through it (cell membrane allows to some substrates to pass through, but it restricts the pass of another substrates). This property is called selective permeability.

The permeability of the cell membrane depends on several factors related to the chemical and physical characteristics of the substance which wants to pass trough as solubility in lipids, size, charge, nature of the membrane proteins (carriers), etc.

[Byrne, take a look to your notes. Sure that you find a lot of examples of molecules and ions which can pass free through the membrane, which pass to the cytoplasm by proteins, etc].
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