Cellular transport
Ch 5 (Hon. Bio)
Ch 4 (Bio)
Passive Transport
Movement of substances from HIGH
concentration to LOW concentration.
Movement DOWN a concentration gradient.
 Just like rolling downhill
 Requires NO energy
 Three types of passive transport:
Diffusion
Facilitated Diffusion
Osmosis

Diffusion

Diffusion – Movement of substances from
high concentration to low concentration.


These substances move through the membrane
WITHOUT HELP.
Equilibrium – Molecules move down their
concentration gradient until there are
equal amounts on both sides.

Equilibrum = Equal (even)
Diffusion of Sugar
!!!WATCH IT HAPPEN!!!
Osmosis

Osmosis - the diffusion of water (across a
membrane) from high concentration of
water to a lower concentration of water.

Water will move
toward the high
concentration of solute
(and hence a lower
concentration of
water).

Salt is a solute; when it is concentrated inside or
outside the cell, it will draw the water in its direction.
This is also why you get thirsty after eating
something salty.
Hypotonic solution




"HYPO" means less;
there are more solute
(salt) molecules inside the
cell and less in solution.
water will move into the
cell.
The cell will gain water
and grow larger.
Hypertonic Solution




"HYPER" means more; in
there are less solute (salt)
molecules inside the cell
and more in solution.
water will move out of the
cell.
The cell will lose water and
shrink.
Isotonic Solution

"ISO" means the
same

EQUAL amounts of
water moves in and out
of the cell at the same
time.
 The
cell is at
EQUILIBRIUM with the
solution.
Turgor Pressure

Turgor Pressure – the pressure water
exerts against the cell wall.
 Lack
of turgor pressure = wilting or
plasmolysis
 Too much turgor pressure = bursting or
cytolysis
Facilitated Diffusion

Facilitated Diffusion – movement of
substances that are too large to cross the
plasma membrane
 These
substances are "helped" across by
carrier proteins
Active Transport
Movement of substances from LOW
concentration to HIGH concentration.
 Movement AGAINST a concentration
gradient.
 Just like climbing uphill.
 REQUIRES energy

Sodium Potassium Pump - the cell pumps out 3
sodium ions and takes in 2 potassium ions. Ions
move from low to high concentration…REQUIRES
ENERGY
Endocytosis



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Endocytosis - cell takes in large particles by engulfing
them
Endo = ENTER
Pinocytosis-fluids
Phagocytosis-large particles
Exocytosis
Exocytosis - cell gets rid of particles
 Exo = EXIT

The examples, videos, and
illustrations were taken from a
variety or websites.