Download PASSIVE TRANSPORT Words You Should Know: Diffusion Osmosis

PASSIVE TRANSPORT
Words You Should Know:
Diffusion
Osmosis
Gradient
Equilibrium
Selectively Permeable
Passive Transport
Active Transport
Isotonic
Hypertonic
Hypotonic
Contractile Vacuole
Carrier Protein
Facilitated Diffusion
Selectively Permeable - membranes that only allow certain molecules to pass through
Concentration gradient - a difference between concentrations of solutes in solutions
During passive transport, molecules move with the concentration gradient, from areas of high concentration
to areas of low concentration.
Think of food coloring that spreads out in a glass of water, or air freshener sprayed in a room.
Diffusion - the process by which molecules spread from areas of high concentration, to areas of low
concentration. When the molecules are even throughout a space - it is called EQUILIBRIUM.
Facilitated diffusion – takes place when large or polar molecules cannot cross the cell membrane on their
own, and need to "helped" across by carrier proteins.
Osmosis - the diffusion of water (across a membrane)
Osmosis is an example of passive transport, so
water will move to the area that has a high
concentration of solute (hence a lower
concentration of water).
Less solute = more water
More water = less solute
The solute is less concentrated on the left side
to begin with, which means there is more water
on the left side. This causes the water to move
from the left side of the membrane to the right
side until homeostasis (equilibrium) is reached.
Diffusion and Osmosis are both types of PASSIVE TRANSPORT. This means that there is no energy is required
for the molecules to move in or out of the cell.
These vocabulary words refer to the solution that the cell is surrounded by, NOT the solution within the cell.
Type of Solutions
"ISO" means the same – referring to solute
If the concentration of solute (ex. salt) is equal on both sides, the
water will move back in forth at the same rate, so the size of the
cell stays the same.
"HYPO" means less – referring to solute
In this case, there is less solute (ex. salt) molecules outside the
cell, which means there is more water outside the cell. Because
water moves from areas of high concentration to areas of low
concentration, more water will move into the cell.
The cell will swell up (grow larger) because more water is entering
the cell than leaving the cell.
In plant cells, the central vacuoles will fill and the plant becomes
stiff and rigid, the cell wall keeps the plant from bursting. In
animal cells, the cell may be in danger of bursting, organelles
called CONTRACTILE VACUOLES will pump water out of the cell to
prevent this.
"HYPER" means more – referring to solute
In this case, there is less solute (ex. salt) molecules inside the cell,
which means there is more water inside the cell. Because water
moves from areas of high concentration to areas of low
concentration, more water will move out of the cell.
The cell will shrink (get smaller) because more water is leaving the
cell than entering the cell.
In plant cells, the central vacuole loses water and the cells shrink,
causing wilting. In animal cells, the cells also shrink. In both cases,
the cell may die.