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Osmosis. 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. Osmosis. Diffusion of water molecules
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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. 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
Concentration Gradient Water Potential Gradient
Membrane is impermeable to large sugar molecules but permeable to small water molecules
H2O Selectively permeable membrane
Water balance 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
Passive transport • http://www.youtube.com/watch?v=sdiJtDRJQEc&feature=related (osmosis, 1 min) • http://www.youtube.com/watch?v=JShwXBWGMyY (passive transport, 5 min)
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
2. Active transport • Uses chemical energy from ATP • Move molecules against the concentration gradient (low conc. high conc.)
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
HYPOTONIC ISOTONIC HYPERTONIC ANIMAL CELL Shriveled Normal Lysed PLANT CELL Flaccid Turgid Plasmolysed
NORMAL SHRIVELED EXPANDED ISOTONIC HYPERTONIC HYPOTONIC