Molecules can cross cell membranes by passive transport, which may be diffusion of (C02, O2, H20)or (_____) of polar molecules and ions.
What's the blank, and is the chemicals in the first parenthesis correct?
(Text doesn't give clear answer)
Thanks!
The blank is "facilitated diffusion." The chemicals in the first parenthesis, CO2, O2, and H2O, are correct examples of molecules that can cross cell membranes by diffusion.
Diffusion is the spontaneous movement of molecules from an area of higher concentration to an area of lower concentration. This process occurs without the need for energy input.
Facilitated diffusion, on the other hand, involves the movement of certain polar molecules and ions across the cell membrane with the help of transport proteins. These transport proteins facilitate the movement of molecules that are unable to diffuse freely across the cell membrane due to their size or charge.
The text you provided mentions that passive transport, which includes both diffusion and facilitated diffusion, can allow molecules to cross cell membranes. This means that in addition to the small, nonpolar molecules like CO2, O2, and H2O, larger polar molecules and ions can also pass through the cell membrane via facilitated diffusion. However, the specific examples of polar molecules and ions that can be transported through facilitated diffusion are not mentioned in the text, so we cannot be sure exactly which specific chemicals are being referred to in the blank.