Download Chapter 9 Homeostasis and the Plasma Membrane

Diffusion, Osmosis, Homeostasis and the
Plasma Membrane
Maintaining a Balance
Organisms must
adjust to changes
in their
environment.
If not…DEATH!
Cellular Transports
NO ENERGY REQUIRED
 Diffusion (passive)
 Facilitated Diffusion (passive)
 Osmosis-Diffusion of Water (passive)
ENERGY REQUIRED
 Active Transport
II. Brownian Movement
A. 1827 Robert
Brown
B. Evidence of the
random motion
of molecules
I. Diffusion
A. Diffusion - the
process by which
molecules spread
from areas of
high
concentration, to
areas of low
concentration.
B. Passive
Transportrequires no
energy
H. Facilitated Diffusion
(Transport Proteins, passive)
 Channel proteins
simply act as a passive
pore. Molecules will
randomly move
through the opening in
a process called
diffusion. This requires
no energy, molecules
move from an area of
high concentration to
an area of low
concentration.
B. Concentration
gradient - a
difference between
concentrations in a
space.
C. When the
molecules are even
throughout a space
- it is called
Dynamic
EQUILIBRIUM
III. Osmosis
A. Osmosis - the diffusion of water
molecules through a selectively
permeable membrane. Passive
Transport
Ex.Water will move in the direction where
there is a high concentration of solute (and
hence a lower concentration of water).
H2O 
conc. of solute
(copy this)
Osmosis
 Watch this animation of
water molecules moving
across a selectively
permeable membrane.
Water molecules are the
small blue shapes, and
the solute is the green.
 The solute is more
concentrated on the right
side to start with, which
causes molecules to
move across the
membrane toward the
left until equilibrium is
reached.
IV. Isotonic Solution- Equal on both
Sides!
If the concentration of
solute (salt) is equal on
both sides, the water will
move back and forth but
it won't have any result
on the overall amount of
water on either side.
A."ISO" means the same
Conc solution=Conc. of cell
V. Hypotonic Solution-Hypo means
less!
A.
B.
C.
D.
There are less solute
(salt) molecules in the
solution. Water will move
into the cell.
Salt “Sucks” or dehydrates
the water
C. The cell will gain water
and grow larger. In plant
cells, the central vacuoles will
fill and the plant becomes
stiff and rigid, the cell wall
keeps the plant from
bursting-Turgor Pressure
D. 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.
VI. Hypertonic Solution- "HYPER“
means more!
A. There are more
solute (salt)
molecules in
solution, which
causes the water
to leave the cell
B. Plants wilt and
animal cell shrinkPlasmolysis. In
both cases, the cell
may die.
IX. Active Transport
A. Move particles from a region of
lesser concentration to a region
of greater concentration. Move
against the concentration
gradient. Must use energy (ATP)
B. Types of Active Transport
1. Exocytosis- To
expel wastes,
secrete
substanceshormones.
 Requires Energy
2. EndocytosisPhagocytosis-cell
“eating” engulfs food
Pinocytosis- cell
“drinking”
cell surrounds and takes
in material from its
environment. Engulfed
and enclosed by a
portion of the cell’s
plasma membrane. That
portion breaks away and
the resulting vacuole
with its contents moves
to the inside of the cellrequires ATP(ENERGY
C. Carrier Proteins Using ATP
1. Some proteins actively
use energy from the
ATPs in the cell to drag
molecules from area of
low concentration to
areas of high
concentration
(working directly
against diffusion) an
example of this is the
sodium/potassium
pump. Here the energy
of a phosphate (shown in
red) is used to exchange
sodium atoms for
potassium atoms.