(H2O O 5人 (H20(H20(H2O A A. Diffusion b. Bulk flow
A. Diffusion B．Bulk flow A B
OSmoSIS Movement of water across a selectively semi-permeable membrane in response to chemical and pressure gradients (together water potential) Selectively semi-permeable membrane prevents exchange of solutes, but allows passage of water
Osmosis ➢ Movement of water across a selectively semi-permeable membrane in response to chemical and pressure gradients (together = water potential). • Selectively semi-permeable membrane prevents exchange of solutes, but allows passage of water
B 纯水 糖液 半透性 膜
Water Potential oncept Water potential the free energy associated with water= potential for doing work Water moves down a water potential gradient (from higher to lower potentials)=gives up energy as it moves W一上Ew △ 片 w
Water Potential ➢ Water potential = the free energy associated with water = potential for doing work. ➢ Water moves down a water potential gradient (from higher to lower potentials) = gives up energy as it moves
Water Potential Water potential is not an absolute value. It is relative to a reference state Reference state= pure water at ambient temperature and pressure The water potential within a cell is usually less than the reference state
Water Potential ➢ Water potential is not an absolute value. It is relative to a reference state. • Reference state = pure water at ambient temperature and pressure. ➢ The water potential within a cell is usually less than the reference state