movement across p.m

diffusion:

• down its conc gradient, high to low conc.
• doent need energy.

osmosis:

• diffusion of water, from a more dilute solution to a more conc solution.
• isotonic = w.p to a cell = no diffusion of water
• hypertonic - w.p then a cell = water out of cell
• hypotonic + w.p then a cell = water into cell

w.p:

• the effective conc of of free water.
• water always falls from high to low w.p