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Homeostasis & Transport
Chapter 7
Section 7.3 & 7.4
Two Main Types of
Transport
Passive Transport:
Does not need energy
Active Transport:
Needs energy
Like floating down a river, passive transport does
NOT need energy to occur
Passive
Transport
Diffusion – molecules move across a given space
without the use of energy from High
concentration to low concentration
Osmosis-specifically water moving across a
membrane without the use of energy from HC
LC
Facilitated Transport- No energy, “help” moving
from HC LC (channel, carrier proteins)
Substances move until they are balanced throughout a
space; until the inside of the cell and outside of the cell are
equal. This is called a state of equilibrium; homeostasis.
Osmosis : Three solutions
Water will move from an area of high concentration to an
area of low concentration until equilibrium is reached.
1. Hypotonic –water moves into the cell (cell
can “pop”) Example: Distilled water.
Cytolysis – cell bursting (animal cells may burst but plant
cells won’t because they have a cell wall)
2. Isotonic – no movement; equal concentration
of water on each side of the membrane. Ex. Tap
water, spring water, purified water
3. Hypertonic – water moves out of the cell (cell
shrinks- called plasmolysis) Ex. Salt water,sugar
water. http://www.youtube.com/watch?v=gWkcFU-hHUk
Plant cell
Watering a Plant
(Think of blowing up a balloon)
Turgor Pressure -as water enters the
plant cell. The cell wall is strong
enough to resist the pressure exerted
by the water inside the expanding cell.
The pressure that water molecules
exert against the cell wall is Turgor
Pressure.
Plasmolysis- Cell shrinks away from
the cell wall, turgor pressure is lost.
Plant begins to Wilt
Solute concentration –particles inside and outside the
cell, effecting whether water moves INTO the cell, or
OUT of the cell.
More solutes less room for water
Less Solutes More room for water
Think of two beakers same size and shape, filled
with water.
Now drop rocks into one of the beakers. Which
beaker has more water in it?
Which one has Less?
We can see the results of that demo
but sometimes you can’t see the
solute. Ex salt
More Sugar
(solute) Less room
for water.
Therefore, this is
the Low
Concentration
Lab
•
•
•
•
Elodea
Red onion
Potato
Dialysis tubing
Elodea:
http://www.youtube.com/watch?v=V
K-_YHakvho
Onion
http://www.youtube.com/watch?v=J
aCCKPyE6I4&feature=related
Bio
Rocks!
Like paddling upstream, active
transport requires a lot of
energy!
Endocytosis- process
where the cell
membrane extends
outward and envelops
food particles.
1. Phagocytosis-if the
material taken in is
organic matter
2. Pinocytosis-takes
in liquids
http://www.youtube.com/watch?v=4
gLtk8Yc1Zc&NR=1
ExocytosisDischarge of
materials from
vesicles at the cell
surface.
Protists contractile http://www.youtube.com/watch?v=K7yku3sa
vacuole discharge 4Y8&feature=related
waste, water.
Animal cells- provide a mechanism for secreting
many hormones, neurotransmitters, digestive
enzymes, tears and other substances.
Excretion: CO2, sweat, urine
Active Transport
Usually form Pumps
Used to move independent of gradient
LC HC
Cells that perform a lot of active
transport, require a lot of
Mitochondria.
Nerve and Muscle cells (both perform a
lot of active transport)
Two Main Types of Pumps
• Almost all of the active transport in animal
cells is carried out by only two kinds of
pumps:
1. The sodium-potassium pump and
2. The proton pumps.
1/3 of the body’s energy is
used to work this pump!
• This flow of ions is vital for restoring a
balance needed to keep a nerve cell
functioning.
Na+/K+ pump: Very Important !
1. Carrier protein has a shape that allows 3 Na + to enter
2. ATP splits, phosphate attaches to carrier (split by
enzyme in carrier)
3. Change in shape allows 3 Na +’s to be dumped outside
cell
4. New Shape allows 2 K+’s to enter carrier protein
5. Phosphate group is released (conformational change)
6. Carrier protein changes back to original shape,
releasing 2 K +’s inside the cell.
http://www.you
tube.com/watch
?v=9CBoBewd
S3U
Na+/K+ pump continued
Pump results in concentration gradient and electrical
gradient across the cell.
3 Na+’s outside cell, 2 K+ inside cell.
Outside is more positive than the inside of the cell.
Na+ via diffusion, 300 Na per sec per carrier
Cl- are attracted to the positive Na,
they diffuse through the channel
For Robin: http://www.youtube.com/watch?v=6v5o9AzjH6Q
Membrane potential. . . Charge difference between
the inside and outside of the membrane.
The charge difference is due to the difference of
concentrations of ions on either side of the cell
membrane.
Inside the membrane is negative and the outside is
positive. This is due to the permeability of ions.
There are more Na+ ions in the extracellular fluid
and more K+ ions in the intracellular fluid. The
membrane is more permeable to K+ which leaks
out to the outside of the membrane giving it a
positive charge.
http://www.youtube.com/watch?v=iAGdkje6pg&feature=related
Cystic Fibrosis
Inherited disorder, caused by a faulty Cl- ion channel
Thick mucous collects in airways (respiratory
system) and in pancreatic and liver ducts. (digestive
system)
(high solute concentration out of the cell, watery
mucous) No Cl- can enter the cell.
Liver ducts-clogged, liver becomes cirrhotic less
working liver tissue-liver transplant
Age about 28-30 with meds, liver trans,gene therapy
works in mice not humans (yet)
http://www.pbs.org/wgbh/nova/genome/media/2809_q056_09.html