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random movement of molecules down a concentration gradient from area of high solute concentration to and area of low solute concentration
Factors Affecting Rate of Diffusion
1. Molecular Weight- larger molecular weight solutes will not cross semi-permeable membrane.
2. Temperature- high temp increases kinetic energy thus increasing rate of diffusion
3. Polarity- polar substances diffuse inw ater more easily
4. Permeability of membrane- ioniztion properties of different solutions retard rate of diffusion
5. Concentration of substance- more concentration equals more diffusion
type of diffusion involving movement of H2O across semi-permeable membrane
-SPM prevents solute particles from crossing but allows solvent molecules (H2O) to move freely
-solvent moves from high to low solvent concentration
hydrostatic back pressure required to cancel osmotic diffusion of H2O from one side of osmometer to the other
Calculation of Osmotic Pressure
pi = iRT (C1-C2)
pi - osmotic pressure
i= total # of ions dissociated from each molecule in solution
R- gas constant
T= temp (K)
M= molarity= C1 and C2
C1= concentration gradient of sucrose in bag (moles/L)
C2= concentration gradient of sucrose in beaker (moles/L)
ability of extracellular solution to cause a change in the shape or size of cell
*always named in respect to extracellular environment
Cell in hypertonic solution
-solvent rushes out of the cell
-cell shrivels (crenates)
animal cell crenation = plant cell plasmolysis
Cell in hypotonic solution
-solvent rushes into the cell
-cell bursts (lysis)
hemolysis-> bursting of red blood cell
Tonicity and Erythrocytes (red blood cells)
cells in distilled water- swell and burst
cells in concentrated salt solution- shrivel
Tonicity and Plant Cells
cells in distilled water- stiffen but retain shape
cells in concentrated salt solution- cell body shrinks and pulls away form cell wall
disruption of homeostasis
cells in body swill with increased consumption of salt
varies from bloating to pitting
when the channels help dissolve the large molecules that pass through the membrane
when the water molecules are more numerous or stronger outside of cell so they all rush into cell causing it to swell
when the concentration is weaker within the cell so all the molecules rush out causing it to deflate
Occurs in walled cells; the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.
the combined effect of solute concentration and pressure. The formula is pressure plus osmotic potential (which is always negative). Measures the tendency of water to leave one cell compartment for another
Limp; lacking firmness, as in plant cell surroundings where there is no tendency for water to enter the cell.
the driving force of the net flow of molecules in or out of a cell, no energy is needed to drve the flow since all the movement is due to the greater concentration of molecules on one side than the other.
Order in which water moves in plants
the soil -> roots -> leaves (water potential from high to low-negative)
In your experiment, as solute is added to the water in the beaker, what happens to the potato cells?
When a solute is added, the water potential of the solution becomes negative. This means that water must flow from the higher water potential inside the potato cell to the lower water potential outside the potato cell until the two are equal. In this experiment's terms, this means that the potatoes would lose weight to water.
Why does a low concentration of solute result in a high water potential
water molecules have a lot of potential energy because they are free to move around and not bound to solute
How does water travel to the leaves from the roots?
As transpiration happens, this leads to the formerly higher water potential in the leaves to becomes water potential that is lower than that at the roots. This causes the water to want to move from high to low water potential. The way it beats gravity is by cohesion and adhesion.
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