Why cant it diffuse directly from the air (where it seems there would be a high concentration of oxygen) to the interior of the cell (where there would be a lower concentration)? Why must it first dissolve in water?
I know that it must have to dissolve because worms and other organisms must be moist to respire…and our lungs have to moist…but why is this so?
WAG What do you suppose would happen to you if your lungs looked like a dried up mud caked river bed?
Why is water described as “the water of life?”
When the water is gone you are nothing more nor less than the dust of the earth!
The short answer to the OP? That’s the way it works!
Our circulatory system pumps liquid, not gas. So to transport gases, they must be in the liquid. Furthermore, the inside of the cells are liquid. Anything in them must be in the liquid.
Maybe i’m not making myself clear.
i’m not talking about transport, or our circulatory system.
oxygen diffuses across the cell membrane, right?
however, to do so, it must FIRST dissolve in water.
my question is, why?
why cant oxygen molecules in the air diffuse across the cell membrane into the cytoplasm?
why do they have to dissolve first?
I think that’s just restating the OP. What principle prevents gasses from diffusing into liquids? Surface tension? Relative densities?
i dont think we’re talking about the same thing.
i’m not asking why water is essential to life. i’m asking why water seems to be essential to the diffusion of gases into a cell. why cant oxygen molecules that are in the air move directly across the cell membrane and enter the cell? why must they first dissolve in water?
Because it’s not air that surrounds your cells. It’s water. That’s all there is to it.
Why do you have to first walk through my yard before walking in my door? Because there’s a yard around my house.
yes! thank you, i’m glad someone understood what i’m asking.
i think there is more to it than that. forget about my cells for a second. take an earthworm, whose respiratory surface is its outside skin. if the worm dries out, it cant get the oxygen that it needs. why? once the moisture is gone, so what? why cant oxygen still diffuse into the cells?
the fact that it cant implies that oxygen dissolving in water is somehow essential to its diffusion into the cell.
It’s because as it dries out, that means those cells are shriveling and dying. Cells must be hydrated to function, because all of their proteins and such need to stay in solution. The oxygen can’t get past a barrier of dead, dried-out cells very well.
ok… so u’re essentially saying that there DOESNT have to be water for the diffusion to occur – its just that without water, the cell dies due to drying out ( because the water inside moves outside from osmosis) and then the oxygen has trouble moving past THAT.
well…that seems like a good answer. thanks.
i wonder what it is about the dead/dying cells that prevents oxygen from diffusing across them?
My guess would be something analogous to convection is part of the transfer mechanism, not just diffusion.
can you explain?
The structure of the cell’s plasma membrane requires water on the outside (the hydrophilic head groups), without water the membrane would be destabilized.
So the oxygen must first dissolve in water to diffuse because the water is essential for the membrane. I agree the way it is worded is confusing perhaps it should be worded: Cells must have a layer of water to maintain their plasma membrane so the oxygen must first dissolve in that layer of water before it can diffuse into the cell.
Welcome to the boards, sunshine1. You perhaps may not have noticed that you’re responding to a discussion from 7 years ago… so, you may not get much reaction from the original participants.