Download Osmosis Diffusion

Semi-permeable Membrane
• Only allows certain
molecules to pass
through
– Smaller polar
molecules pass easily
– Large molecules or
nonpolar molecules do
not pass through
The Structure of the
Cell Membrane
Outside
of cell
Inside
of cell
(cytoplasm)
Passive
CellularTransport:
No energy
Required!
I.Passive transport: when a cell
moves molecules from high
to low concentration
A. No energy required
A. Diffusion
1. Net movement of
molecules from high
concentration to low
concentration, down
their concentration
gradient
Ex. Perfume molecules
spreading out in a
room
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Sugar Molecules
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Sugar Molecules
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Sugar Molecules
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a. Diffusion rate depends on size of
molecules, concentrations and
temperature
b. Diffusion never stops!
– Molecules just move back and forth slowly
even when they are at equilibrium
c. Diffusion requires no energy!
B. Osmosis
1. Net movement of water
molecules across a semipermeable membrane, from
a high concentration to a low
concentration of water
2. No energy is needed
ex. Elodea Plasmolysis
Osmosis
Higher Concentration
of Water
Water molecules
Cell
membrane
Lower Concentration
of Water
Sugar molecules
3. Which way will water flow?
a. Hypotonic Solution: when there is
less solute (stuff) outside than inside the
cell – Water moves into the cell
Uh...Oh!
SPLAT
b. Hypertonic Solution: when there is more
solute outside than inside the cell - Water
moves out of the cell
Solutes
Cell
shrinks
c. Isotonic: the concentrations inside and
outside the cell are the same (equilibrium)
- Water moves in and out of the cell at the
same rate
Solutes
Cell
shrinks
AAARRGHH!
Uh...Oh!
SPLAT
Osmosis & Diffusion ?’s
• What do we call the process when a sugar
cube dissolves in a cup of water?
• Osmosis is a type of diffusion. However, what
is being diffused in osmosis?
• Draw a picture showing what would happen to a
raisin put in a cup of water overnight?
III. Facilitated Diffusion: molecules
are moved across the membrane
by carrier proteins
A. Still moving from high to
low concentration
No Energy
Needed!
B. Why would a molecule need
a carrier protein?
1. too big to fit through pores,
not soluble in lipids (glucose)
C. Carrier proteins have
specific shapes for specific
molecules (Lock and Key)
IV. Diffusion through ion channels:
help ions move across
membrane
A. Specific for each ion
Ions
Active
Cellular Transport
Energy Required!
ATP
I. Active Transport: when a
cell uses energy (ATP) to
move molecules up their
concentration gradient
ATP
A.Cell Membrane Pumps: carrier
proteins that “pump” materials
up their concentration gradient
1. Revolving Door: as some
come in some come out
Requires
energy
B.Endocytosis and Exocytosis
1. Used when materials are
too large or when lots of stuff
is moved into or out of the cell
2. Energy is required!
a. Endocytosis: when cells
take in stuff from the outside
b. Exocytosis: when a cell
releases contents outside the cell
?
?