Diffusion

1
Diffusion is the movement of molecules from areas
of high concentration to areas of low
concentration. An example is when you open a
bottle of perfume the molecules spread out in the
room.
Diffusion also occurs through the semi-permeable
cell membrane. Molecules which can go directly
through the cell membrane or through carrier
protein channels. Using a protein channel is
called facilitated diffusion. Both move molecules
from high concentration to low concentration,
flowing down the concentration gradient.
Eventually the molecules will be equally
dispersed the cell is said to reach
equilibrium.. ( inside outside )
Explanation animation of cell transport
United streaming website videos
Diffusion
Diffusion also high and low temp
United streaming passive transport
2
Osmosis is the diffusion of water from high
concentration to low concentration.
An isotonic solution contains the same
concentration of solutes as does the cell.
Therefore, water moves across the cell membrane
equally in both directions.
A hypotonic solution contains less solutes than
the cell. (Distilled water) Therefore the water
concentration surrounding the cell is higher.
Water moves into the cell the cell swells.
Hypo sounds like hippo. The cell can burst
cytolysis. (cyto cell lysis burst)
A hypertonic solution contains more solutes than
the cell. (Salt water) The water concentration is
higher inside the cell. Water moves out of the
cell the cell shrinks. Plasmolysis cell
shrinkage.
osmosis hypo and hypertonic solutions
Osmosis cell into 3 beakers hypo, hyper isotonic
osmosis with addition salt to one side
3
United streaming website videos
Active transport moves molecules from low to high
concentration which is up the concentration
gradient. Since this requires an output of energy
it is called active transport.
Explanation animation of cell transport
4
Objectives
Contrast passive and active transport.
Warm Up

• For each of the following choose either passive
  or active transport.
• Diffusion
• Osmosis
• Ion pump
• Moving molecules from high to low concentration
• Uses ATP to move the molecules across the
  membrane.
• Endocyctosis

Passive
Passive
Active
Passive
Active
Active
5

• Explain the difference between passive transport
  and active transport.
• Passive diffusion moves molecules from high
  concentration to low concentration.
• Active moves molecules from low to high
  concentration requires energy (ATP).
• 2. What function do carrier proteins perform in
  active transport?
• The protein binds to the specific molecule
  transports them up the concentration gradient.
• 3. What provides the energy that drives the
  sodium-potassium pump?
• The removal of a phosphate from ATP.
• 4. Explain the difference between pinocytosis
  phagocytosis.
• Pinocytosis brings liquid into the cells
  phagocytosis brings solids by wrapping the cell
  membrane around them then extruding them on the
  other side.
• 5. Describe the steps in exocytosis.
• The vesicle binds to the cell membrane and then
  opens on the other side to release the contents.

6
Ion pumps are carrier proteins which use active
transport. Some cells must have a higher
concentration of sodium ions outside the cell a
higher concentration of potassium ions inside the
cell.The sodium-potassium pump first binds 3
sodium ions on the cytosol side of the cell. A
phosphate group is split off an ATP attaches to
the protein channel which causes it to change
shape allow the Na ions across to the outside
of the cell. The channel is now the correct shape
to bind to 2 potassium ions which cause the
release of the phosphate group the transport of
the potassium ions to the inside of the cell.
United streaming website videos
different types of cell transport
active transport explanation
animation of active transport
7
Endocytosis exocytosis are used to transport
substances too large to pass through the cell
membrane or through protein channels.
In endocytosis cells ingest fluids,
macromolecules large particles by surrounding
them with the cell membrane which then forms a
vesicle. Pinocytosis transports fluids into the
cell. (cell drinking) Phagocytosis transports
solids into the cells.
In exocytosis vesicles within the cell fuse with
the cell membrane then release their contents
to the outside of the cell.
phagocytosis animation
cholesterol endocytosis digestion