Experiment showing osmosis What is osmosis What is

• • • Experiment showing osmosis What is osmosis? What is water potential? Water potential of sucrose solution Water movement across a differentially permeable membrane • Osmosis and plant cells • Osmosis and red blood cells

Experiment showing osmosis 30 minutes later

What is osmosis? • The net movement of water molecules across a differentially permeable membrane from a less concentrated solution to a more concentrated solution • The net movement of water molecules across a differentially permeable membrane from a region of higher water potential to a region of lower water potential

What is water potential? • The probability of water molecules moving through a membrane from each side of the differentially permeable membrane • Value as the concentration of solutes (i. e. as the concentration of water molecules ) • Distilled water: water potential = 0 greatest water potential • Solutions: water potential < 0 (-ve value)

Water potential of sucrose solution + Water potential 0 (arbitrary unit) - 0 Concentration of sucrose solution (M)

Water movement across a differentially permeable membrane low water potential high water potential water molecule net movement sucrose of water molecules

Osmosis and plant cells When young plant cells are immersed in • distilled water they become turgid, bigger and heavier

Osmosis and plant cells When young plant cells are immersed in • concentrated sucrose solution they become soft, smaller and lighter

Osmosis and red blood cells When red blood cells are immersed in • distilled water they burst and release red pigments

Osmosis and red blood cells When red blood cells are immersed in • concentrated sucrose solution they shrink

Summary • Osmosis: the net movement of water molecules across a differentially permeable membrane down a water potential gradient • Effect of osmosis