Download Diffusion and Osmosis - I`m Curious

Biology
Name:
Membrane Transport
Getting across the Membrane
Selectively Permeable - membranes that allow some things through, the cell
membrane is selectively permeable, water and oxygen move freely across the
cell's membrane, by diffusion
Diffusion and Osmosis
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
Define These from your text Notes!
Concentration gradient SoluteFacilitated Diffusion:
.
.
.
OSMOSIS
Water molecules move across a selectively
permeable membrane. 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.
Osmosis - the diffusion of water (across a membrane)
Water will move in the direction where there is a high concentration of solute (and hence a lower
concentration of water.
Biology
Name:
Membrane Transport
A simple rule to remember is:
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.
Type of Solutions
If the concentration of solute (salt) is equal on
both sides, the water will move back in forth
but it won't have any result on the overall
amount of water on either side.
"ISO" means the same
Biology
Name:
Membrane Transport
The word "HYPO" means less, in this case there are less solute (salt) molecules
outside the cell, since salt sucks, water will move into the cell.
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
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.
The word "HYPER" means more, in this case
there are more solute (salt) molecules outside
the cell, which causes the water to be sucked
in that direction.
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.
This is why it is dangerous to drink sea water - its a myth that drinking sea
water will cause you to go insane, but people marooned at sea will speed up
dehydration (and death) by drinking sea water.
This is also why "salting fields" was a common tactic during war, it would kill
the crops in the field, thus causing food shortages.
Biology
Name:
Membrane Transport
Diffusion and Osmosis are both types of PASSIVE TRANSPORT - that is, no
energy is required for the molecules to move into or out of the cell.
Sometimes, large molecules cannot cross the plasma membrane, and are
"helped" across by carrier proteins - this process is called facilitated diffusion.
ACTIVE TRANSPORT
Active Transport - this type of transport requires that the cell use energy,
because substances are moving against the concentration gradient.
Sodium Potassium Pump - the cell pumps out 3 sodium ions and takes in 2
potassium ions. Our cells constantly create a high concentration of sodium
outside the cell. As sodium comes back in it brings glucose along with it.
Now you understand why sports drinks like Gatorade contain sodium and
potassium.
Endocytosis - cell takes in large particles by engulfing them
Exocytosis - cell gets rid of particles, opposite of endocytosis
Biology
Name:
Membrane Transport
Sample Test questions
Glucose can’t freely cross any cell membrane. Imagine a creature with cells
that did not have a sodium/potassium pump. Instead the creature had large
channel proteins that let glucose freely flow into the cell.
What advantage would this cell have (think of energy)?
What disadvantage would this cell have(Use the word diffusion correctly in your
answer)?
Most restaurants bring you dressing on the side when you order a salad. If
dressed ahead of time the salad wilts and becomes slimy after 10 minutes.
1) Use the terms osmosis, isotonic, hypotonic, and hypertonic to explain what
happens to the salad.
2) Keep in mind that salad has a lot of salt in it.
3) Compose your explanation as a comic strip in the frames on the next page.
Include color and have fun 
Biology
Name:
Membrane Transport
Your comic here…
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