2.6.1 Osmosis governs the movements of water across cell membrane

Osmosis pressure渗透压: tendency for water to move by osmosis

Tonicity is the ability of a solution to cause a cell to gain/lose water

Isotonic: solution=cell

Hypertonic: solution>cell, the cell loses water

Hypotonic: solution<cell, the cell gains water

Turgor细胞膨压

Plasmolysis质壁分离

2.6.2 Osmoregulation is a form of homeostasis

Osmoregulation: 渗透调节

2.6.3 Water potential

Water potential (Ψ) = Ψp + Ψs

Ψp = pressure potential (external force)

Ψs = solute potential

Water in open container and animal cells has a Ψp =0

Plant cells has a Ψp>0

Ψs = -iCRT

i = ionization constant for the solute