Can some one please explain to me osmosis - osmotic pressure - diffusion- and transport of substances across?

diffusion is simply the movement of molecules from a greater concentration to a lesser concentration. all molecules move or vibrate unless at absolute zero. hence this movement occurs natrually. osmosis is simply the movement of water molecules from a greater concentration to a lesser concentration across a semipermeable membrane(cell membrane) or more simply put the diffusion of water. osmotic pressure occurs when the molecules essentially are trapped in an enclosed space and can not readily move freely. This causes them to strike each other more frequesntly and thus the pressure increases within this confined area(think central vacuaole of plant cell) eventually this pressure will prevent any more water from entering the cell inspite of their being pressure differential between the amount of molecules outside the cell as compared to inside the cell. Large molecules, molecules of lesser concentration outside the cell than inside, or molecules that might be repelled by the membrane must be transported across the membrane using energy from the cell in order to accomplish this task unlike the pive means water and small molecules take to p through the cell membrane