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2.04 – CELL TRANSPORT:
DIFFUSION AND OSMOSIS
Biology 11
TRANSPORT- PASSIVE OR ACTIVE
|
|
Passive transport-the movement of materials
across a cell membrane without the expenditure
of cell energy
Active transport-the
transport the use of cell energy to move
materials across a cell membrane (against
concentration gradient)
PASSIVE TRANSPORT
| From
high to low
concentration
| Does not require
q
energy from the cell
Diffusion
Osmosis
y Facilitated diffusion
y
y
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ACTIVE TRANSPORT
| From
low to high concentration
energy from the cell
| Requires
Active
A
i transport proteins
i
Endocytosis
y Exocytosis
y
y
DIFFUSION & OSMOSIS
KINETIC MOLECULAR THEORY
|
All molecules are moving.
|
Solid, liquid, gas
|
Brownian Motion– the random movement of
molecules suspended in a liquid or gas.
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DIFFUSION
|
The NET movement of particles from an area
of high concentration to an area of low
concentration
Q: What is a concentration gradient??
WHAT IS A CONCENTRATION GRADIENT?
| Concentration
Gradient
the difference in concentration
of solutes in a given space
| Diffusion
happens when
substances
b t
move “down”
“d
”a
concentration gradient (from
high to low) until the
concentration of the two areas
becomes equal.
ENDING: DYNAMIC EQUILIBRIUM
| At
dynamic equilibrium there is
no NET movement of particles.
|
|
DYNAMIC implies movement
EQUILIBRIUM implies a balance
y
y
No longer a concentration gradient
Particles move equally in all directions
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DYNAMIC EQUILIBRIUM
NOTE: At D.E. particles are still moving, its just that
overall, they will remain “mixed” unless acted upon by
another force. (So no “net” movement overall).
DIFFUSION
OSMOSIS
|
The diffusion of WATER across a
selectively- permeable membrane.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBooktransp.html
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OSMOSIS DEMOS
http://www.biologycorner.com/bio1/diffusion.html
#
| http://www.emc.maricopa.edu/faculty/farabee/BI
OBK/BioBooktransp.html
|
DIFFUSION VS. OSMOSIS
| Diffusion
is the NET movement of particles
from an area of high concentration to an area
of low concentration!”
| Os
Osmosis
os s iss just a “special
spec a case oof d
diffusion”.
us o .
It is the diffusion of water across a
selectively permeable membrane.
| Sometimes
we refer to this movement as
being from an area of HIGH water potential
to an area of LOW water potential.
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BUT WHAT IS
“WATER POTENTIAL”??
| Water
potential is the measure of the ability
of water to move (always from high to low) .
| Think
of osmosis as the net movement of
water (remember water is also just a particle)
down its concentration gradient.
WHAT IS THE CAUSE OF DIFFUSION?
|
|
Diffusion happens because of the random kinetic
energy (energy of motion) of particles and the
existence of a concentration gradient.
All matter is made of particles and those
particles are constantly in motion.
WHAT AFFECTS THE RATE OF
DIFFUSION IN CELLS??
|
5 Things:
1.
Temperature
2.
Charge
3.
Diameter (Size) of particle
4.
Concentration gradient (difference in
concentration)
5.
Surface Area of membrane
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SOLUTIONS
The movement of water in and out of cells gives
rise to 3 different conditions:
1.
2
2.
3.
Isotonic Solutions
Hypotonic Solutions
Hypertonic Solutions
Solute = The substance that dissolves to form a solution
Solvent = A substance, usually a liquid, in which other
substances are dissolved
ISOTONIC
solutions have equal (iso-) concentrations of
dissolved substances. Solute concentrations
are the same outside the cell and inside.
|
(Equal amounts of water movement in and
out of the cell, with a net flow is zero).
Ideal environment
HYPOTONIC
|
solutions are those with less solute
present and more water.
– concentration of water is higher
outside the cell than inside.
(Water will move INTO THE CELL)
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HYPERTONIC
|
solutions are those in which more solute is
present than water.
– concentration of water is lower outside
the cell than inside.
((Water will move OUT OF THE CELL))
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