Chapter 5.5 - Osmosis Flashcards
Definition of solute
Substance dissolved in solvent forming a solution
Concentration
Amount of solute in a certain volume of aqueous solution
Definition of water potential
Pressure exerted by water molecules as they collide with membrane or container
Unit for water potential
Pa pascals or kPa kilo pascals Greek letter psi
Water potential of pure water
0kPa at standard rtp and atm pressure (-25*C and 100kPa)
Effect of presence of solute in water
Lowers water potential below zero
Osmosis
Net movement of water molecules from a region of higher water potential to a region of low water potential across a partially permeable membrane. Happens until equilibrium.
Diffusion of water into closed system
Increase in hydrostatic pressure. kPa. Dangerous at cellular level and potentially damaging.
Cytolysis
Animal cell is placed in solution with higher water potential. Water moves in and hydrostatic pressure increases. Membrane cannot withstand pressure so cell bursts.
Crenation
Placed in solution of lower water potential than cytoplasm, water leaves cell. Reduction in volume and cell puckers.
Prevention of cytolysis and crenation
Control mechanisms that makes sure water potential of aqueous solution is equal to water potential in cell (blood plasma)
How do plants control water potential around themselves
They can’t
What happens when pressure in plants increases
Cell membrane pushes against rigid cell well due to increase in hydrostatic pressure. Pressure against cell wall is called turgor. When water is being resisted, cell is turgid.
Plasmolysed
Plant cell in solution of lower water potential loses volume in cytoplasm. Cell surface membrane pulled away from cell wall.
