- #1
Cheman
- 235
- 1
Transport across cell membranes...
I was reading my textbook and it said, "Fat-soluble molecules, such as glycerol, can diffuse through the membrane easily. They dissolve in the phospholipid bilayer and pass through it in the direction of the concentration gradient, from a high concentration to a low concentration. Water, oxygen and carbon dioxide can also diffuse through the bilayer, passing easily through the temporary small spaces between the 'tails' of the phospholipids which result from its fluidity. However, ions of any size, most polar molecules and most large molecules cannot diffuse through the phospholipid bilayer. They have to go through the protein pores."
I can understand why large molecules would be unable to pass through, ( cause they are too big to go through the gaps) but why are ions of any size and polar molecules unable to?
Thanks in advance. :-)
I was reading my textbook and it said, "Fat-soluble molecules, such as glycerol, can diffuse through the membrane easily. They dissolve in the phospholipid bilayer and pass through it in the direction of the concentration gradient, from a high concentration to a low concentration. Water, oxygen and carbon dioxide can also diffuse through the bilayer, passing easily through the temporary small spaces between the 'tails' of the phospholipids which result from its fluidity. However, ions of any size, most polar molecules and most large molecules cannot diffuse through the phospholipid bilayer. They have to go through the protein pores."
I can understand why large molecules would be unable to pass through, ( cause they are too big to go through the gaps) but why are ions of any size and polar molecules unable to?
Thanks in advance. :-)