Topic 5: Diffusion and Osmosis

diffusion

random movement of molecules - does not require energy - move down concentration gradient (high to low)

where is diffusion faster, why?

diffusion is faster in liquids & gases because molecules move more freely - molecules more rapid at higher temperatures.

cytoplasm

solution of proteins, salts, and ribosomes in water

semi-permeable membrane

cell membrane - regulates which molecules pass in and out of the cell

osmosis

special case of diffusion where two solutions of different concentrations are on opposite sides of the semi-permeable membrane

what is the movement of osmosis?

solvent (water) crosses membranes freely, solutes cannot. lipid nature of the cell membrane prevents large or charged molecules from passing through

list some substances that can pass the membrane freely

water, oxygen, carbon dioxide

list some substances that cannot pass the membrane freely

salts, sugars, proteins, nucleic acids, other charged molecules

chemical potential (µ)

measure of the free energy available to do the work of moving one mole of molecules (higher solute concentration, higher chemical potential)