1. Osmosis
Very important topic – must be covered prior to 2.1 Internal. Must also complete a number of practicals as background and formative work for the Internal.

2. } Transport mechanisms Passive transport (doesn’t require energy)
Diffusion
Facilitated diffusion
Osmosis
Filtration
Active transport (uses energy from ATP)
Active transport
Bulk transport }
Movement down a concentration gradient

3. 3. Osmosis
Diffusion of water molecules through a selectively permeable membrane, from an area of high water potential to an area of low water potential NB: Water potential gradient is opposite to solute concentration gradient. High water potential = low solute concentration

4. Concentration Gradient
Water Potential Gradient

5. Membrane is impermeable to large sugar molecules
but permeable to small water molecules

6. Selectively permeable membrane
H2O
Selectively permeable membrane

7. Water balance COPY Why is OSMOSIS important for living organisms?
Osmo-regulation - maintaining the right levels of water in cells is vital for life.
HOMEOSTASIS – maintain balance / equilibrium
Water moves between cells in a multi-cellular organism
COPY

8. Passive transport
(osmosis, 1 min)
(passive transport, 5 min)

9. } Transport mechanisms Passive transport (doesn’t require energy)
Diffusion
Facilitated diffusion
Osmosis
Filtration
Active transport (uses energy from ATP)
Active transport
Bulk transport }
Movement down a concentration gradient

10. 2. Active transport Uses chemical energy from ATP
Move molecules against the concentration gradient (low conc.  high conc.)

12. Tonicity is a relative term
Hypotonic Solution - lower concentration than another solution
Hypertonic Solution - higher concentration than another solution
Isotonic Solution - both solutions have same concentration

13. HYPERTONIC ISOTONIC HYPOTONIC Shriveled Normal Lysed Flaccid Turgid
ANIMAL CELL
Shriveled
Normal
Lysed
PLANT
CELL
Flaccid
Turgid
Plasmolysed

14. NORMAL
SHRIVELED
EXPANDED
ISOTONIC
HYPERTONIC
HYPOTONIC