Transcript Cellular Transport Osmosis and Diffusion!

Cellular Transport
Osmosis and Diffusion!
IMPORTANT DEFINITIONS
• DIFFUSION: movement of particles from
higher concentration to lower
concentration
• OSMOSIS: diffusion of water across a
selectively permeable membrane
In a cell, water always tries to reach an equal
concentration on both sides of the
membrane!
DIFFUSION
OSMOSIS
What controls OSMOSIS?
1) A concentration gradient (unequal
distribution of particles on each side of a
membrane).
During osmosis, only water
diffuses across the selectively
permeable membrane.
OSMOSIS
ISOTONIC SOLUTIONS!
• Concentration of dissolved substances in solution
is the same as concentration of dissolved
substances inside the cell.
• Water inside cell is equal to water in solution.
• Cells in isotonic solution do not experience osmosis
and retain their normal shape.
• EX: Immunizations are isotonic solutions so they
do not damage the cells by gain or loss of water.
HYPOTONIC SOLUTIONS!
• Concentration of dissolved substances is lower in
solution outside the cell than concentration inside
the cell.
• There is more water outside the cell than inside.
• Cells in hypotonic solutions experience osmosis in
which water moves through membrane into cell.
• EX: In animal cells, the pressure inside cell
increases causing the cells to swell and sometimes
burst!
• EX: In plant cells, the rigid cell wall prevents
bursting, but the cells become more firm.
CUCUMBERS IN THE MIST!
HYPERTONIC SOLUTIONS!
• Concentration of dissolved substances outside cell
is higher than concentration inside cell.
• There is more water inside cell than outside.
• Cells in hypertonic solutions experience osmosis in
which water moves through membrane to
outside of cell.
• Ex: In plant cells, membrane and cytoplasm
shrink away from cell wall and plant wilts.
• EX: In animal cells, the pressure decreases and the
cells shrivel.
Don’t be so SALTY!
Passive Transport: Mosey on
through…
• Molecules pass through the membrane by
diffusion requiring no extra energy.
Ex: water & lipids
• Ion Channels
-type of passive transport that uses
membrane proteins to pass certain ions.
Exp. Cl- Na+ Ca2+
Passive Transport
Passive Transport
Facilitated Diffusion: Help them
out a bit!
Remember those transport proteins in the
phospholipid bilayer? Here’s where they fit
in!
• Facilitated diffusion: passive transport
across membrane with help of transport
proteins.
• Ex: sugars & amino acids
Active Transport: ENERGY
REQUIRED!
• Active transport is the movement of
materials through a membrane across a
concentration gradient.
• This requires energy to counteract the
movement of diffusion from high to low
concentrations!
How does it work?
1) Transport protein called “carrier protein”
binds with particle that is going to be
transported.
2) Energy is required.
3) Proteins can continue this process over
and over.
-Active transport allows a particle
movement into or out of a cell against a
concentration gradient.
Exp. Na out of the cell, K into the cell.
How carrier proteins work!
Active Transport
Active Transport
Cellular Transport
What about the big
boys?
• ENDOCYTOSIS: cells surrounds and takes in
material from environment by engulfing the
material! YUMMY!
• EXOCYTOSIS: cells expel materials from cell, such
as waste or indigestible particles. GROSS!
• Both endo and exocytosis are moving large
masses of material and require energy (ACTIVE
TRANSPORT!)
Endocytosis
Exocytosis