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5.4 Osmosis. T he diffusion of water across a membrane Depends on solute concentration inside and outside of cell W ater moves across a membrane until the concentration of solute is equal on both sides of the membrane Type of passive transport. Lower concentration of solute. Equal - PowerPoint PPT Presentation
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5.4 Osmosis• The diffusion of water across a membrane
– Depends on solute concentration inside and outside of cell
– Water moves across a membrane until the concentration of solute is equal on both sides of the membrane
– Type of passive transport
Selectivelypermeablemembrane
Solutemolecule
Lowerconcentration
of solute
H2O
Solute molecule withcluster of water molecules
Net flow of water
Watermolecule
Equalconcentration
of solute
Higherconcentration
of solute
5.5 Water Balance: Tonicity• Tonicity:
o the ability of a solution to cause a cell to gain or lose water
o dependent on the concentration of a solute on each side of the membrane
5.5 Water Balance: Tonicity– Isotonic indicates that the concentration of a solute is
the same on both sides
– Hypertonic indicates that the concentration of solute is higher outside the cell
– Hypotonic indicates a higher concentration of solute inside the cell
Osmosis: Isotonic Solutions
Osmosis: Hypertonic Solutions
Osmosis: Hypertonic Solutions
Osmosis: Hypotonic Solutions
Osmosis: Hypotonic Solutions
Isotonic solution
(B) Lysed (C) Shriveled
(D) Flaccid (E) Turgid (F) Shriveled
Hypertonic solutionHypotonic solution
Plantcell
Animalcell
(A) NormalPlasma
membrane
(plasmolyzed)
5.5 Water Balance: Osmoregulation• Osmoregulation: ability to maintain water balance within cells
– prevents excessive uptake or excessive loss of water
– Plant, prokaryotic, and fungal cells have different issues with osmoregulation because of their cell walls
– Organisms that live in freshwater are constantly pumping water out of their cells because they live in a hypotonic environment.
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