Osmosis Flashcards
cell controls the __ hence controlling __.
type and amount of channel protein synthesized, the type and quantity of the substances that cross the membrane.
osmosis
the diffusion of water across the membrane from a region of lower solute concentration (hypotonic) to a region of higher solute concentration (hypertonic)
solvation process
solvent (water) molecules surround and interact with solute particles (remove them from the crystal grid)
what reduces the effective number of water molecules
when water molecules are bound to solute molecules because they can’t move freely then
- a solution with high C(solute) has max bound H2O
H2O mmoelcules cross the membrane by:
1|simple diffusion (to a small extent)
2|osmosis (facilitated diffusion) - aquaporins
what do aquaporins do and where can they be found
they greatly increase membrane permeability to water molecules and they can be found in kidney cells and plant root cells
examples of one-celled organisms with and without a cell wall
without - amoeba, paramecium
with - diatoms, chlamydomonas, cyanobacteria
what does the cell do in order to prevent bursting in a hypotonic solution?
it uses energy from ATP to pump ions into contractile vacuoles so that the water from the cytoplasm enters the vacuole - the vacuole then merges with the plasma membrane and water is removed from the cell using exocytosis
how does having a cell wall impact the life of the cell in a hypertonic solution
it’s the same as in organisms that do not have a cell wall (doesn’t prevent plasmolysis) - the plasma membrane detaches from the cell wall and the cell shrinks (as the vacuole dehydrates)
how does having a cell wall impact the life of the cell in a hypotonic solution
it prevents the cell from bursting by maintaining its shape and keeping it turgid
when is the water potential maximal
in pure water, equal to 0 kPa
plasmolysis
when in a hypertonic environment water leaves the cell so it shrinks and the plasma membrane detaches from the cell wall (vacuole also shrinks and dehydrates)
deplasmolysis
when a dehydrated cells is placed in water and water reenters it (cell increases in volume and the membrane again attaches to the cell wall)
water potential
- potential force held by water per unit of volume (unit is kPa)
- the absolute WP cannot be measured
what is WP at standard conditions
pure water under no pressure and at standard temperature, WP = zero and this is the maximal value of WP!!
