Download Osmosis in Red Blood Cells

CH. 3 ~ CELLS
Cell Membrane
1. Surrounds ALL cells
2. Has a “Phospholipid bilayer” which
makes it “flexible and “fluid”
Cell Membrane
“Phospholipid bilayer”
- Phosphate ‘head’ (polar- hydrophillic)
- 2 Lipid ‘tails’ (nonpolar- hydrophobic)
- What is “Polar” vs “Nonpolar”?
Water Molecule
2 Hydrogen Atoms + 1 Oxygen Atom
A water molecule is a ‘polar’ molecule because
it has a partial negative charge on one side and
a partial positive charge on the other side.
When the Hydrogen atom of
one water molecule is
attracted to the oxygen atoms
of another water molecule a
hydrogen bond is formed.
Lipids are Nonpolar molecules
Cell Membrane
3. Semi-permeable – only allows certain
substances to pass through
4. Contains proteins- some used for
identification and some for transport (that
help to pass materials through).
Transport of materials
into and out of the cell
• Passive Transport – movement of molecules
that does not require energy.
– Usually from high concentration to lower
concentration
ex. Diffusion, Osmosis, Facilitated diffusion
• Active Transport – movement of molecules
that requires energy.
– Usually from low concentration to high
concentration (against the concentration gradient)
ex. Pumps, endocytosis, exocytosis
Passive
Active
• Diffusion
• Pumps
• Osmosis
• Endocytosis
• Facilitated
Diffusion
• Exocytosis
Terms:
• Equilibrium – when 2 given areas have the
same concentration of molecules.
• Concentration Gradient – the difference in
concentration of molecules in 2 given areas.
(Ocean- swimming with the tide or against it- which requires energy?)
• Defines HOW molecules will move, if going
WITH the concentration gradient (from high to
low = passive transport) or AGAINST it (from
low to high = requires energy = active transport
Passive Transport:
1. Diffusion –
movement of
molecules from
an area of high
concentration to
an area of lower
concentration.
Passive Transport:
2. Osmosis – diffusion of water
3. Facilitated diffusion – passive transport of
materials across a cell membrane using
protein channels.
Facilitated Diffusion
(complete on back of the notes)
Protein Channels
Carrier Proteins
Facilitated Diffusion
Increases the rate of diffusion
• Similar to simple diffusion in the sense that
it is diffusion (across a membrane) from a
high concentration to a lower
concentration.
• However, this time the rate of diffusion is
greatly accelerated by the action of
membrane proteins that act as carrier
molecules and aid in diffusion.
http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html
Passive vs. Active
Transport
• Passive Transport - Transport
processes that happen "passively"
without the cell needing to expend any
energy to make them happen.
• Active Transport - transport processes
that require energy from the cell's
reserves to "power" them.
Pictures of Passive and
Active Transport
(complete on back of the notes)
Using a
Protein
Channel
Energy Added
Using a Protein
Pump
Pumps
• Type of active transport
• Move molecules from an area
of LOW concentration to an
area of HIGH concentration
ACTIVE
Na-K (sodium-potassium) Pump
ACTIVE
Endocytosis
• Intake of material (food) using
the cell membrane
• Cell membrane surrounds
material and encloses it –
forming a vesicle/vacuole.
Amoeba Eating
ACTIVE
Exocytosis
• Removal of material (waste) from a cell.
• Golgi Apparatus “packages” the material
into a vesicle and sends it to the cell
membrane
• The vesicle fuses with the membrane
• The material is deposited outside the cell
Exocytosis
Endocytosis and Exocytosis
(complete on back of the notes)
http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html
PASSIVE
ACTIVE
NO ENERGY
ENERGY
• Diffusion of
perfume, food
coloring
• Osmosis
• Facilitated diffusion
– Protein channels
– Carrier proteins
• Exocytosis
– GA packages and
secretes wastes
• Endocytosis
– Membrane
surrounds and
engulfs food, etc.
(Amoeba)
• Pumps
– Sodium-Potassium
Electron Micrograph of
Exocytosis
•
This figure was taken from Alberts et al, Molecular Biology of the Cell,
Garland Publishing Third Edition, 1994
DIALYSIS DEMO
• The small molecules of water and iodine
moved from an area of high concentration,
outside the cell, to an area of low
concentration inside the cell in order to try
to reach equilibrium. The large molecules
of starch were not able to diffuse and
reach equilibrium because they were too
large to pass through the semi-permeable
membrane.
Solute vs. Solvent
Osmosis and Tonicity
• Solution – a homogenous (same throughout)
mixture
• Solvent – the substance in a solution that
dissolves other substances (solutes)
• Solute – the substance in a solution that is
dissolved.
Another way to think about it:
a solute is dissolved in another
substance, known as a solvent.
Usually, the substance present in
a greater amount is considered
as the solvent.
Which is the solute? Solvent? Explain your
rationale
water and kool-aid.
WATER IS THE UNIVERSAL SOLVENT
Osmosis
• A type of
diffusion
• The movement of
WATER from an
area of ______
concentration to
an area of ____
concentration
There are 3 types of osmotic
solutions
• Hypotonic – there is a greater
concentration of solute (ie, salt, the
‘stuff’) in the cell then in the fluid
around the cell
• Hypertonic – there is a greater
concentration of solute (ie, salt, the
‘stuff’) in the solution than in the cell
• Isotonic - equilibrium
Another way to think about it
• Hypotonic – more water outside the
cell, therefore water rushes into the cell
• Hypertonic – more water inside the cell,
therefore water rushes out of the cell
• Isotonic – same amount of water inside
and outside the cell so nothing
changes
Whenever solutes (dissolves substances) are added to water, they decrease
the number of free water molecules; more solute molecules, fewer free water
molecules
Osmosis in
Red Blood Cells
Osmosis in
Red Blood Cells
Hypo
Iso
Hyper
Osmosis in a Plant Cell
Hypo
Iso
Hyper
Osmosis in a Plant Cell
Comparison of Plant and Animal
Cells in Osmotic Solutions
What is the major differences between what
happens in plant and animal cells when placed
in a hypotonic solution?
PASSIVE
ACTIVE
• Material only
moves DOWN
the
concentration
gradient (from
HIGH to LOW
concentration).
• Material can
move up OR
down the
concentration
gradient since
energy is used
to move the
material.
• http://www.nclark.net/BioChapter8
Animation
• www.biologycorner.com/bio1/diffusion.html
• http://www.nclark.net/BioChapter8