Download Plasma Membrane

CELL TRANSPORT
Define these terms:
1. Solute *
2. Solvent *
3. Semipermeable Membrane*
4. Passive Transport*
5.Active Transport*
6. Diffusion*
7. Osmosis*
8. Concentration Gradient
9. Facilitated Diffusion
10. Hypertonic
11. Hypotonic
12. Isotonic
How do molecules get into
the cell?
•By crossing the Cell
Membrane!
What is a key property of
the Cell Membrane?
• Selective Permeability!!
• This property of biological
membranes allows some
substances to cross more
easily than others.
How much energy will it
cost the cell to MOVE
molecules in or out?
• It depends on HOW it enters the cell!
• Which do you think does NOT “cost”
the cell energy- Passive Transport
or ActiveTransport?
PASSIVE
TRANSPORT
First type Passive Transport-
Diffusion
• What is it?
– Random movement of molecules down
a concentration gradient from an area
of high concentration to an area of low
concentration.
• NO energy is expended.
• ALWAYS high concentration to low concentration!
Diffusion
Watch this animation!
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/c
hapter2/animation__how_diffusion_works.h
tml
• http://www.indiana.edu/~phys215/lecture/le
cnotes/diff.html
2nd type Passive TransportOsmosis
• The diffusion of water across
selectively permeable membranes.
• Water moves from a high water
concentration to low water
concentration.
• NO energy expended by cell
3nd type passive transport
Facilitated Diffusion
Type which uses transport
proteins to move molecules
across the membrane WITHOUT
any energy expended by cell!
Always high concentration to Low
concentration
Question:
What’s in a Solution?
Answer:
• solute +
solvent

solution
• NaCl
H 20

saltwater
+
Hypertonic
• A solution with greater solute concentration
(less water) compared to inside the cell.
3% NaCl
97% H2O
Red Blood Cell
solution
5% NaCl
95% H2O
Hypotonic
• A solution with lower solute concentration
(more water) compared to inside the cell.
3% Na
97% H2O
Red Blood Cell
solution
1% Na
99% H2O
Isotonic
• A solution with an equal solute concentration
compared to inside the cell.
• This solution is said to be in Dynamic
equilibrium.
3% Na
97% H2O
Red Blood Cell
solution
3% Na
97% H2O
Movement of H2O = OSMOSIS!
• Water will “ALWAYS” diffuse down a
concentration gradient from a HYPOTONIC
solution (more water, less solute) to a
HYPERTONIC solution (less water, more
solute).
ALWAYS REMEMBER- water moves from
• HYPOTONIC 
HYPERTONIC
Animal Cells
• Animal cells placed into a hypotonic
solution will EXPLODE.
Hypotonic
Red
Blood
Cell
Animal Cells
• Animal cells placed into a hypertonic
solution will SHRIVEL.
Hypertonic
Red
Blood
Cell
Plant Cells
• In a hypotonic environment, the vacuole is full
of water (cell gains water), and the cell
membrane is pushed against the cell wall. The
cell wall helps the plant cell retain its shape
under the tension.
Water
Cell
Wall
Water
Central
Vacuole
Water
Plant Cells
• In a hypertonic environment (loss of water),
the plasma membrane pulls away from the
cell wall (vacuole empty).
Water
Water
plasma membrane
Cell
Wall
Water
Active Transport
• The movement of molecules
(small or large) across the plasma
membrane using energy (ATP).
Examples of Active
Transport:
Active transport using a carrier
molecule in the membrane
- many times, this involves moving
molecules from a low to high
concentration (OPPOSITE the
direction during diffusion!).
- Requires ATP (ENERGY!!) to move
it across!
Protein pumps
• Some membrane proteins use energy to
pump substances in and out of the cell.
• Sodium potassium pump animation.
• How are large molecules
transported into and out of
the cell?
• Endocytosis and Exocytosis
(BOTH are active transport!)
Endocytosis
• ENTRY into cell
• Portion of the membrane surrounds or
engulfs a macromolecule (large molecule)
outside cell. The membrane pinches off to
form a vesicle in the cytoplasm
• Requires Energy!!
Endocytosis, cont.
Different names for type macromolecules
endocytosed:
– Pinocytosis: endocytosis of liquids
– Phagocytosis: endocytosis of
particles
– http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/phagocitos
is.swf
Endocytosis, cont.
• Amoeba feeding
Exocytosis:
• EXPORT of materials OUT of
the cell (wastes, cell products)
- Also
a type of Active Transport
(energy required!!)
MODELLING A CELL
MEMBRANE
Plastic baggies are a lot like
cell membranes; they are
semipermeable.
• Do baggies allow
any of the
following - water,
starch, or iodine to move through
them?
• Materials:
1.baggies
2.Starch suspension
in H2O
3.Iodine solution
4.Beakers
Wrap up of Transport across a
Semipermeable membrane!
• BEFORE you get your beaker,
write down what you EXPECTED
to happen? (Who moved across
the plastic membrane?)
How did your experiment work?
• Did the liquid in the beaker or the
baggie change color? What does it
indicate?
• Decide WHICH molecules were
transported- water, iodine, or
starch?
• Did your experiment test all 3
components?
Cont….
• Things to think about:
– Size of atoms/ molecules
– Set-up of experiment- could you
detect movement of ALL molecules?
– Validity/ reliability
• How is the baggy LIKE a cell
membrane?
• How is it NOT LIKE a cell membrane?
Wrap-up!
• Standard 10.1: FUNDAMENTAL life
processes depend on the physical and
chemical activities of the cell.
– D30. Explain the role of the cell
membrane in supporting cell functions.
• What ARE the roles of the cell
membrane?
Wrap-up!
How is the cell membrane
structured to ensure
efficiency and survival?
DO Now!
• Sheet 3.5
–Complete and we will discuss it
Concentration Problems
In each problem below, the membrane is
permeable to water only!
1. Which way will water move – into or
out of the body cell? (draw an arrow!)
2. The solution is ________.
3. Which way will water move – into or
out of the sphere? (draw an arrow!)
4. Is the solution in the beaker
hypotonic, isotonic, or hypertonic
compared to the cell? (Circle one!)
5. Which way will water move – into
or out of the sphere? (draw an
arrow!)
6. What will happen to the shape / size
of the sphere? What is the solution
outside the cell?
7. Which way will water move –
into or out of the body cell? (draw
an arrow!)
Cell
0.45 M
solute
0.35 M solute
8. What is the cell’s solute concentration
after dynamic equilibrium is reached?
9. Which way will water move – into
or out of the body cell? (draw an
arrow!)
cell
10. What is the cell’s water concentration
after dynamic equilibrium is reached?