module 2 - 5.5 osmosis Flashcards
how is a solution formed?
solute dissolved in a solvent (always water) to form a solution
what is concentration?
amount of solute dissolved per unit volume of solvent
what is water potential?
pressure exerted by water molecules as they hit a container or membrane
what does water potential quantify?
quantifies the tendency of water to move from one area to another due to osmosis and hydrostatic pressure effects
what does it mean to quantify something?
give it numbers
what is hydrostatic pressure?
pressure of water
what is osmosis?
specific type of diffusion
why is osmosis a specific type of diffusion?
because it applies only to water molecules moving across a partially permeable membrane down a concentration gradient
what is osmosis explained in terms of?
water potential
what is the water potential of pure water?
0kPa
why is osmosis diffusion?
because it is the solvent molecules moving within solute molecules
how will the water move by osmosis?
from area of high WP to low WP through a partially permeable membrane until equilibrium has been reached
what leads to a hydrostatic pressure?
movement of water into cells causing the cell volume to increase
can animals increase/decrease in hydrostatic pressure?
no - they cannot increase nor decrease
what does it mean if cell if a cell is hypertonic?
a solution with a higher WP compared to the cell (cells shrivel)
- causes cells to be crenelated
what does it mean if a cell is isotonic?
a solution with the same WP as the cell (equal)
- causes equilibrium
what does it mean if a cell is hypotonic?
a solution with a lower WP compared to the cell (cells burst)
- causes cytolysis
why do cells go through cytolysis/ crenelation?
plasma membranes can’t stretch easily and have no mechanical strength to withstand hydrostatic pressure
what are erythrocytes?
red blood cells
which is more dense: red blood cells or plasma
plasma
what happens when water enters a plant and increases the hydrostatic pressure?
the strong cellulose cell wall can withstand the pressure and the cell becomes turgid
cells do not suffer from cytolysis, so what happens when they do not have enough water in them?
they become plasmolysed/ cell is hypertonic
what happens to a cell when a cell has too much water in it?
cell becomes turgid/ cell is hypotonic
what happens when water movement is in equilibrium in and out of a plant?
cell becomes flaccid/ cell is isotonic
is there higher water potential in or out of cytoplasm in plants?
higher WP out of cytoplasm in plants
what happens to plasma membrane when plant cell is flaccid/ isotonic?
plasma membrane ‘peels’ away from cell wall, contents no longer pushing against cell wall
