Passive transport the movement of

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Passive transport the movement of (NO ENERGY
C0ST) substances across a
cell membrane without

the use of cellular energy.
Diffusion is the movement of
molecules from an
area of higher concentration
to an area of lower
concentration. Concentration gradient-
Concentration of molecules across a

space.
Diffusion refers to the process by which
molecules intermingle as a result of their
kinetic energy of random motion.

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Transport Mechanisms
http//www.wiley.com/legacy/college/boyer/04700037
90/animations/membrane_transport/membrane_transpor
t.swf
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• Kinetic Energy
• Molecules in constant motion
• Equilibrium
• molecular concentrations become the same
  throughout
• the constant motion of molecules occur even when
  equilibrium
• 
  has been reached.

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Diffusion Across Membrane

• Semi Permeable membrane
• some materials may pass, but not all
• What can pass and what cant
• Those substances that can dissolve in lipids
• Non polar substances such as
• CO2
• O2 dissolve in lipids
• Very small polar molecules

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O2
CO2
H2O
Amino Acids
Proteins
Carbohydrates
Ions
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Osmosis

• Is a process by which water
• moves from an area of higher
• concentration to an area of lower
• concentration through a
• Semi permeable membrane.
• Is a form of Passive transport-
• No additional energy is
• required

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Cycling of Matter in Livings Systems
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Osmotic Pressure
Cycling of Matter in Livings Systems
Osmotic Pressure
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-Hypotonic solution - Solute outside the
cell is lt than that inside the cell.
(solute Material being
dissolved) Ex 20 solute concentration (80
water) inside the cell 10 solute
concentration (90 water) outside the cell.
Which way will the net flow of water
go? Remember only the water flows in
Osmosis.
10/90 hypotonic
20/80 hypertonic
Semi permeable membrane
If the cell had no way to regulate water
concentrations Cytolysis-
bursting of the cell would occur
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Isotonic solutions Inside and outside
concentrations are
The solutions are at equilibrium ( there is an
flow of molecules
in all directions.)
Hyper-Hypo-Iso refer to relative solute
concentrations of 2 solutions.
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In Osmosis- water flows to the
hypertonic solution.
Hypertonic Solution
The solute concentration - outside the
cell gt inside the cell
10/90 hypertonic
5/95 hypotonic
Plasmolysis would take place. The
shrinking or wilting of a cell placed in a
hypertonic
solution. If the cell had no way to regulate
water concentrations
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How Cells Deal With Osmosis
Have isotonic external environments 1. keeps
movement of water across the cell
membrane in balance. a. cells
of vertebrates on land b. most
organisms living in the sea Those with hypotonic
cellular environments 1. unicellular freshwater
organisms a. water is in constant motion but
the net gain is
inward. b. lower
concentrations of water in the cytosol
is needed to function normally.
- must rid cells of water
due to osmosis -
contractile vacuoles organelles remove water.
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Contractile Vacuoles continued
REQUIRES ENERGY Ex paramecia
pump water out of the cell. 2. Other cells many
are multicellular organisms, pump
solutes out of the cytosol. This lowers
solute concentrations in the cytosol
and balances the water and solute
levels. Most Plants -live in hypotonic
environments as water flows to the
hyper water is always going into the
cell. - cell wall is needed
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Turgor Pressure
Water pressure within a plant cell. Osmosis
causes water to be pushed
against the cell wall.
hypotonic
Hypertonic
Hypertonic environment causes water to
leave. Plasmolysis will occur- shrinking or
wilting of a cell in a
hypertonic
environment
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Cell Structure and Functions
http//www.tvdsb.on.ca/westmin/science/sbi3a1/Cell
s/cells.htm
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Cytolysis- Blood Cell have No way to compensate
for changes in solute concentrations
within their environment.
there are NO
contractile vacuoles
solute pumps
cell walls
If placed in a hypotonic solution they
will
BURST Plasmolysis- If placed in a hypertonic
solution they will shrink!
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Facilitated Diffusion- a process in which
substances Move down their concentration gradient
across the Cell Membrane with the assistance of
a carrier protein.
Carrier proteins a protein that transports
specific substances across a biological
membrane.
Carrier Proteins
Transport Protein
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Carrier proteins -serve in facilitated diffusion
down the concentration
gradient NO additional energy is needed for this
process Carrier proteins are used for
-molecules not soluble in lipids
-molecules too large to pass through
the pores in the membrane Example
the transport of glucose is accelerated across
the cell membrane with the assistance of carrier
proteins. No extra energy is needed
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How ?

• Carrier proteins bind to the molecule it
  transports.
• Carrier protein changes shape .
• Shields the molecule from the hydrophobic
• interior of the lipid bilayer.
• 4. The molecule can be transported across the
• cell membrane.
• 5. The molecule Is released from the carrier
  protein .
• 6. Carrier protein returns to the original shape.
  

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• Two important properties of facilitated diffusion
• Can help substances move either into or out
• of the cell depending on the concentration
• gradient.
• 2. Carrier proteins involved in facilitated
  diffusion
• are each specific for one type of a molecule.
  
• Ex Those that assist the passing of simple
  sugars
• do not assist with the diffusion of amino
  acids.

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Diffusion Through Ion Channels Ion channels a
membrane protein that provides
a passageway across the cell
membrane through which an ion
can diffuse Ions such as
Na, K ,Ca, and Cl- -not
soluble in lipids, need assistance
to cross the lipid bilayer
-each type of ion channel is usually
specific for one type of ion
Na ion channel will only allow
sodium ions to pass.
Will not accept calcium chlorine ions
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Some Ion channels are always open Others have
gates that open or close in response to
three kinds of stimuli 1.Stretching of the cell
membrane 2.Electrical signals 3.Chemicals in
cytosol or the external environment.
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Active Transport 5-2

• Active transport- the movement of a substance
• across a cell membrane against a
  concentration
• gradient requires the cell to expend energy.
• Cell membrane Pumps- carrier proteins that
• serve in
  Active Transport.
• They are like that protein carriers that are
  involved
• in facilitated diffusion and work in the same
  manner
• except they require energy.
• 3. Sodium potassium pumps.- a carrier protein
  that
• actively transport K ions into and Na ions
  out
• of the cell.
• In animal human cells it is used to send
  neuro-impulses (action potentials) through
• the body. Higher concentration of Na ions
  outside and higher K ions inside the cell
• is the normal state of a nerve cell before an
  action potential is initiated.

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Active Transport Requires additional
ENERGY!
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The body Uses Na or Cl- ions to 1.
Cause neuro transmission in the body
(neuro impulses) 2. They
cause muscle contractions. Dissolved
dissociated ions- are essential and
present in aqueous solutions found in
all living things. see page 50 figures 3-3
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Cycling of Matter in Livings Systems

• 3 Na ions bind to the carrier protein on the
  carrier protein on the
• cytosol side of the membrane.
• 2. Protein, at the same time, splits a phosphate
  group (hydrolysis)
• from ATP (energy is released)
• 3. Phosphates group binds to the carrier protein.
• 4. Energy changes the shape of the carrier
  protein.
• 5. Protein carries the 3 Na ions across the
  membrane
• 6. 3 Na ions are released outside of the cell.
• 7.Carrier Protein now has the shape it needs to
  bind 2 K ions outside
• the cell.
• 8. When the K ions binds, the phosphate group is
  released.
• 9. Carrier protein changes shape again.
• 10. Carrier protein releases 2 K ions inside the
  cell.
• 11. Process is ready to begin again.
• 12. At top speed the sodium potassium pump can
  transport
• about 450 Na ions and 300 K ions per
  second.
• Na Potassium pumps are just one example. See
  page 1115

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• Endocytosis -process by which cells ingest
• external fluid,
  macromolecules,
• and large particles,
• including other cells
• 1. External materials are enclosed by a portion
  of the cell .
• 2. Cells fold into itself and forms a pouch
• 3. Pouch pinches off, forms the cell membrane
  and become a vesicle.
• 4. Some of the vesicles fuse with lysosomes
  and enzymes digest their contents.
• 5. Other vesicles fuse with other membrane
• bound organelles.

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Endocytosis Energy is Required
This is a type of Active Transport
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• There are two types of Endocytosis is based
• on the kind of material that is taken into the
  cell.
• Pinocytosis involves the transport of solutes
• 
  or fluids.
• 2.Phagocytosis is the movement of large particles
  
• 
  or whole cells.
• -Phagocytes- a cell that engages in
  phagocytosis.
• - allow lysomomes to fuse with vesicles
• that contain ingested bacteria and viruses
• - Lysomal enzymes then destroy harmful bacteria
  
• and virus
  in the body.

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Exocytosis
This is a type of Active Transport

• Vesicles in the cytoplasm fuse with the
• 
  cell membrane.
• 2. Release contents into the cells
• 
  external environment.
• 3. The process may be used to
• a. Export proteins, made in the ribosomes
• b. Packed into vesicles by the Golgi
  apparatus
• c. Fuse with the cell membrane
• d. Diffused outside.
• Ex Exocytosis allows neurotransmitters such as
• norepinephrine or acetylcholine to cross
  the
• neuro cleft (synaspe)

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