The diffusion of a substance across a biological membrane is what?
Passive transport, because no energy is expended by the cell to make it happen
What is osmosis?
The diffusion of water across a selectively permeable membrane
Water diffuses across a from the region of?
Lower solute to higher solute, until it is equal on both sides.
What is the ability of a surrounding solution to cause a cell to gain or lose water?
Tonicity
* Solute concentration is the same as that inside the cell no net water movement across the plasma membrane *
Isotonic solution
Solute concentration is Greater than that inside the cell; cell loses water
Hypertonic solution (shriveling)
Solute concentration is Less then that inside of the cell; cell gains water.
Hypotonic solution (burst)
What creates problems for organisms?
hypotonic and hypertonic environments
The control of solute concentrations and water balance is a necessary adaption for life in such environments.
Osmoregulation
What has a contractile vacuole that acts as a pump?
The protest paramecium, which is hypertonic, to its pond water
Cell walls help maintain what?
water balance
A plant cell in a hypotonic solution swells until the wall opposes uptake; the cell is now what?
Turgid (firm)
If a plant cells surroundings are isotonic, then?
There is no net movement of qater into the cell; the cell becomes flaccid (limp) and the plant may wilt
In a hypertonic environment, plant cells lose water, eventually?
The membrane pulls away form the wall
This is a lethal effect called
Plasmolysis