Osmosis

2 Diffusion of water across a membrane Diffusion of water across a membrane Moves from high water potential (low solute) to low water potential (high solute) Moves from high water potential (low solute) to low water potential (high solute) Diffusion across a membrane Semipermeable membrane

3 Osmosis-Diffusion of H 2 O Across A Membrane High H 2 O Low solute Low H 2 O High solute

Osmosis There are three different types of osmotic solutions: – Hypotonic – Isotonic – Hypertonic

Water Movement 1. Isotonic – Fluid outside the cell has the same concentration of particles as the cytoplasm. No net water movement. 2. Hypotonic – Fluid outside the cell has a lower concentration of particles than the cytoplasm. Water diffuses into the cell. Cell swells! 3. Hypertonic– The fluid outside of the cell has a higher concentration of particles than the cytoplasm. Water diffuses out of the cell. Cell shrinks!

Cell in Isotonic Solution CELL 20% NaCL 80% H 2 O 20% NaCL 80% H 2 O What is the direction of water movement? Water moves both in and out creating equilibrium. ENVIRONMENT NO NET MOVEMENT

Cell in Hypotonic Solution CELL 10% NaCL 90% H 2 O 20% NaCL 80% H 2 O How does the water move? ENVIRONMENT

8 Cell in Hypertonic Solution CELL 15% NaCL 85% H 2 O 5% NaCL 95% H 2 O In what direction does the water move? ENVIRONMENT

Osmotic Solutions (recap) Hypotonic- higher concentration of solutes in the cell Hypertonic- higher concentration of solutes outside the cell Isotonic – equal amount of solutes inside and outside the cell