[sameeralord]

Hello guys,

So there are hydrogen ions inside the cell which is pumped out in cellular respiration.  Now my question is when they say hydrogen ions are inside the cell are these actually dissolved in water, ions can not exist without being dissolved right, why is that they are so reactive otherwise. Also in diffusion when they say hydrogen ions are taken in by the cell, does water come with it because they are dissolved. So does osmosis and ion diffusion occur together. Thanks  

[bromidewind]

Well yes, ions can be solubilized in the cell by a liquid. But they are not required to do such. Plasma is gas composed of ions. I don't actually know if there are any cells which utilize plasma, so it's a fairly moot point.

The H⁺ ions can be dissolved in most any liquid, so it doesn't always have to be water. What happens in cellular respiration is that various enzymes pull the hydrogens off a water molecule then transport them through a series of intermediates to create a proton gradient force. Likewise, other enzymes are removing electrons from donors such as O₂ and pushing them down the opposite direction, creating an electron motive force. Together, these create the electrochemical gradient, the driving force behind the electron transport chain. Eventually, the electrons make their way down to power the ATPase which phosphorlyates an ADP to an ATP, giving energy to the cell. As far as I know, ions are never actually free-floating in cells; they are almost always attached to another molecule or taken from water.

I am confused as to what you mean by "hydrogen ions are taken in by the cell". Typically, cells pump hydrogen ions out, not take them in. The reaction of O₂ with four hydrogens forms two molecules of water which is then either kept in the cell or pumped out. Osmosis is a rather unrelated subject as it has more to do with the concentration of a certain solute inside/outside the cell.

I apologize if any of this is confusing or incorrect; I'm better at describing things with words and pictures, not typing plus, I'm pulling this off the top of my head from what I remember in BioChem. Hope it helps!

[Borek]

The H⁺ ions can be dissolved in most any liquid

That's too strong statement for me. Polar liquid, or better yet polar liquid with free lone pairs sticking from molecules.

[sameeralord]

Thank you very much for the help bromidewind    Ok so my question is simply that when ever ions go through a protein channel or pores through the membrane, is it simple the ion that passes or does the water molecules or any thing attached to it come with it, from your reply it seems that it is just ions and then when they cross the membrane they dissolve with water. Is that what happens?

[Yggdrasil]

The environment inside ion channels has enough polar side groups to solvate ions that go through.  Therefore, one could say that the ion channel is "dissolving" the ions as they pass through the channel.

For proton channels, specifically, the situation is a bit more complex.  The proton channel is lined with water molecules and the binding of a proton at one face of the channel causes the hydrogen bonds in the channel to rearrange such that a proton is kicked off of a water molecule at the other end of the channel.

[sameeralord]

The environment inside ion channels has enough polar side groups to solvate ions that go through.  Therefore, one could say that the ion channel is "dissolving" the ions as they pass through the channel.

For proton channels, specifically, the situation is a bit more complex.  The proton channel is lined with water molecules and the binding of a proton at one face of the channel causes the hydrogen bonds in the channel to rearrange such that a proton is kicked off of a water molecule at the other end of the channel.

Thanks Yggdrasil. Great to have you in this forum