Moving Through the
Plasma Membrane
Let’s Review
• What is homeostasis?
• What is the job of the plasma
membrane?
• How do you think the cell
membrane helps a cell maintain
homeostasis?
Structure and Function
• Phospholipid bilayer with carbohydrates
and proteins imbedded into itself
• Brings in essential materials and excretes
waste products
What does a phospholipid look like?
Polar head/ hydrophilic
Nonpolar head/
hydrophilic
What does the
Plasma Membrane look like?
Outside Cell (Extracellular Matrix)
Protein
Glycoprotein
Cholesterol
Inside Cell (Cytoplasm)
Phospholipids
The Plasma Membrane
Polar
Non-Polar
Outside Cell (Extracellular Matrix)
Protein
Glycoprotein
Cholesterol
Inside Cell (Cytoplasm)
Phospholipids
Plasma Membrane:
The Fluid Mosaic Model
Plasma Membrane:
The Fluid Mosaic Model
• Fluid because
–the phospholipid and protein
molecules are able to move
around. Not stuck in one place.
• Mosaic because
– the membrane contains a variety
of proteins embedded with the
phospholipids.
How do particles move in and
out of the cell?
Permeability of a membrane
• Permeable: anything can pass
through
• Semi-permeable: some things
can pass through
• Impermeable: nothing can
pass through
• The plasma membrane is
described as semi-permeable
because some substances can
move through it:
–Small and
–Non-polar
Passive Transport
energy is
• No additional _______________
required because every particle
has its own energy
• This energy produces
random movement in
________________
particles. (a.k.a Brownian
motion)
Diffusion
• Diffusion is the movement of
high
substances from a ________
concentration to a low
concentration.
• Diffusion is caused by
Brownian Motion
______________________
• Concentration is the amount
_________ of
area
something in a given ______.
Examples of diffusion at work
• Why does food smell fragrant when
cooked?
• Have you ever stood next to someone
wearing strong perfume?
How does it work?
• Particles move down the
concentration gradient, until
equal
the concentration is _________
throughout an area.
• Then the system is said to have
reached dynamic equilibrium.
A.
High Concentration
of Blue Dots
High Concentration of
Orange Dots
Low Concentration of
Orange Dots
Low Concentration of
Blue Dots
B.
System has reached dynamic equilibrium
Back to the plasma membrane…
Outside Cell (Extracellular Matrix)
Inside Cell (Cytoplasm)
Osmosis
• Diffusion of _________
water across a
membrane
• Water molecules can pass through
pores or openings created by
proteins in the plasma membrane .
__________
Back to the plasma membrane…
Outside Cell (Extracellular Matrix)
Protein
Glycoprotein
Cholesterol
Inside Cell (Cytoplasm)
Phospholipids
The Cell’s Environment:
Isotonic
• In an isotonic environment
the solute concentrations
equal and there is no
are ___________
NET movement of water.
The Cell’s Environment:
Hypotonic
• In a hypotonic
environment, there are
less solutes outside
__________
than inside and water
moves into the cell.
The Cell’s Environment:
Hypertonic
• In a hypertonic
environment there are
more solutes outside
_________
than inside and water
moves out of the cell.
Environment Water
outside cell
moves…
Hypotonic
Hypertonic
Isotonic
Effect on
Effect on
ANIMAL cell PLANT cell
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
Swells, then
bursts
(cytolysis)
Hypertonic
Isotonic
In
Animal Cell Cytolysis
Cells burst
Cell still intact
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
Swells, then Swells,
bursts
increases
(cytolysis) turgor
pressure
Hypertonic
Isotonic
In
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
In
Swells, then Swells,
bursts
increases
(cytolysis) turgor
pressure
Hypertonic
Out
Isotonic
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
In
Swells, then Swells,
bursts
increases
(cytolysis) turgor
pressure
Hypertonic
out
Shrinks
(crenation)
Isotonic
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
In
Swells, then Swells,
bursts
increases
(cytolysis) turgor
pressure
Hypertonic
out
Shrinks
Shrink
(crenation) (plasmolysis)
Isotonic
Environment
outside cell
Water
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
In
Swells, then
bursts
(cytolysis)
Hypertonic
Out
Shrinks
(crenation)
Isotonic
Swells,
increased
turgor
pressure
Shrinks,
(plasmolysis)
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
In
Swells, then Swells,
bursts
increases
(cytolysis) turgor
pressure
Hypertonic
out
Shrinks
Shrink
(crenation) (plasmolysis)
Isotonic
Plant cell: Plasmolysis
Plasmolyzed
Cells
Normal cells
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
In
Swells, then Swells,
bursts
increases
(cytolysis) turgor
pressure
Hypertonic
out
Shrinks
Shrink
(crenation) (plasmolysis)
Isotonic
In and
out at
the same
rate
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
In
Swells, then Swells,
bursts
increases
(cytolysis) turgor
pressure
Hypertonic
out
Shrinks
Shrink
(crenation) (plasmolysis)
Isotonic
In and
Stays the
out at
same
the same
rate
Environment Water
outside cell
moves…
Effect on
Effect on
ANIMAL cell PLANT cell
Hypotonic
In
Swells, then Swells,
bursts
increases
(cytolysis) turgor
pressure
Hypertonic
out
Shrinks
Shrink
(crenation) (plasmolysis)
Isotonic
In and
Stays the
out at
same
the same
rate
Stays the same
Osmosis in Action
• What happens when you sprinkle
salt on a slug?
• If you are stranded at sea and run
out of water, should you drink sea
water?
** Water moves from a hypo to a
hypertonic environment.
True or False
1. In diffusion, particles move from
an area of high to low
concentration.
2. Diffusion does not require any
additional energy to occur.
3. Small, charged or polar particles
can move through the cell
membrane by simple diffusion.
What if a cell needs large or
charged/ polar molecules.
Can they move across the
membrane?
Yes!
Selectively Permeable Membrane
• The cell membrane “picks” what
molecules can enter and exit the
cell because proteins in the
membrane allow specific
macromolecules or ions in or
out of the cell.
Facilitated diffusion
• Proteins help particles move
across the membrane
• Transport proteins span the
phospholipid bilayer, but allow
only ___________specific
molecules
through.
>> Selectivity
Types of transport proteins
Ion __________
channels are non–polar on the
• ____
outside and polar on the inside. They
provide a pore for ions and polar
particles to move through.
Carrier_______________
Proteins
• _________
bind to
specific particles, carry them
through the membrane, and release
them on the other side.
http://www.stolaf.edu/people/giannini/flashanimat/transport/caryprot.swf
Remember!
• In diffusion-particles (solutes)
move from an area of HIGH
concentration to LOW In osmosiswater moves from a HYPOTONIC
environment to a HYPERTONIC
environment
• Diffusion requires NO energy input
•
http://scienceguyinatie.blogspot.com/2008/11/cell-membrane-animation-of-word-wall.html
Simple vs. Facilitated
• In simple diffusion, particles move
between phospholipid molecules of
the membrane.
• In facilitated diffusion, particles
move through transport proteins in
the membrane.
• Both do NOT use energy. Particles
must move down the concentration
gradient.
But what if you needed
to move particles
against their
concentration
gradient?
Active Transport
• Transport proteins use
________to
energy move particles against
their concentration gradient,
from a low concentration to a
high concentration.
Sodium-Potassium Pump:
• Carrier- protein that pumps 3
sodium ions (Na+)________
outside
the cell, while pumping 2
potassium ions (K+)________.
inside
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html
http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html
1. 3 Na+ ions from inside the cell bind
to the pump protein. Energy from
ATP is added to the protein.
2. The Na+ ions are moved to the
outside of the cell.
3. The 3 Na+ ions are released and 2 K+
ions bind to the protein.
4. The protein changes back and
releases the 2 K+ ions into the cell.
Vesicle Mediated Transport
• The fluid plasma membrane
can “pinch” off forming vesicles
that can move very
large
_______particles
or lots of
small
______particles.
energy
• This process needs _______.
Endocytosis
• Outside materials are brought
inside the cell.
__________
1) Food
particle
2) Pouch forming
around food
3) Vesicle
with food
Endocytosis
Phagocytosis
• “Cell eating”
• Cell engulfs large food particles
and the vesicle is a food vacuole.
•
http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/phagocitosis.swf
Pinocytosis
• “cell drinking”
• Cell engulfs small droplets of
surrounding fluid.
Exocytosis
• Material from inside the cell is
outsideby vesicles.
released _________
1) Vesicle
fuses with
membrane
2) Pouch
opens
3) Particle
released