Moving through the Plasma Membrane

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Moving through the Plasma Membrane
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What does a phospholipid look like?
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Lets Review

• What is homeostasis?
• What is the job of the plasma membrane?
• How do you think the cell membrane helps a cell
  maintain homeostasis?

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What does the Plasma Membrane look like?
Outside Cell (Extracellular Matrix)
Protein
Glycoprotein
Phospholipids
Cholesterol
Inside Cell (Cytoplasm)
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The Plasma Membrane
Outside Cell (Extracellular Matrix)
Protein
Glycoprotein
Phospholipids
Cholesterol
Inside Cell (Cytoplasm)
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The Plasma Membrane
Polar
Non-Polar
Outside Cell (Extracellular Matrix)
Protein
Glycoprotein
Phospholipids
Cholesterol
Inside Cell (Cytoplasm)
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Plasma MembraneThe Fluid Mosaic Model
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Plasma MembraneThe 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.

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How do particles move in and out of the cell?
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Passive Transport
energy

• No additional _______________ is required because
  every particle has its own energy
• This energy produces ________________ movement in
  particles. (a.k.a Brownian motion)

random
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Diffusion

• Diffusion is the movement of substances from a
  ________ concentration to a low concentration.
• Diffusion is caused by __________ __________
• Concentration is the _________ of something in a
  given ______.

high
Brownian Motion
amount
area
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How does it work?

• Particles move down the concentration gradient,
  until the concentration is _________ throughout
  an area.
• Then the system is said to have reached dynamic
  equilibrium.

equal
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A.
High Concentration of Orange Dots Low
Concentration of Blue Dots
High Concentration of Blue Dots Low Concentration
of Orange Dots
B.
System has reached dynamic equilibrium
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Examples of diffusion at work

• Why does food smell fragrant when cooked?
• Have you ever stood next to someone wearing
  strong perfume?

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Permeability of a membrane

• Permeable anything can pass through
• Semi-permeable some things can pass through
• Impermeable nothing can pass through

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Back to the plasma membrane
Outside Cell (Extracellular Matrix)
Inside Cell (Cytoplasm)
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• The plasma membrane is described as
  semi-permeable because some substances can move
  through it
• Small and
• Non-polar

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Osmosis

• Diffusion of _________ across a membrane
• Water molecules can pass through pores or
  openings created by __________ in the plasma
  membrane .

water
proteins
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Back to the plasma membrane
Outside Cell (Extracellular Matrix)
Protein
Glycoprotein
Phospholipids
Cholesterol
Inside Cell (Cytoplasm)
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The Cells Environment Isotonic

• In an isotonic environment the solute
  concentrations are ___________ and there is no
  NET movement of water.

equal
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The Cells Environment Hypotonic

• In a hypotonic environment, there are __________
  solutes outside than inside and water moves into
  the cell.

less
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The Cells Environment Hypertonic

• In a hypertonic environment there are _________
  solutes outside than inside and water moves out
  of the cell.

more
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Animal Cell Cytolysis
Cells burst
Cell still intact
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Plant cell Plasmolysis
Plasmolyzed Cells
Normal cells
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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.

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True or False

• In diffusion, particles move from an area of high
  to low concentration.
• Diffusion does not require any additional energy
  to occur.
• Small, charged or polar particles can move
  through the cell membrane by simple diffusion.

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• What if a cell needs large or charged/ polar
  molecules. Can they move across the membrane?
• Yes!

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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.

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Facilitated diffusion

• Proteins help particles move across the membrane
• Transport proteins span the phospholipid bilayer,
  but allow only ___________ molecules through.
• gtgt Selectivity

specific
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Types of transport proteins
Ion channels

• ____ __________ are nonpolar on the outside and
  polar on the inside. They provide a pore for
  ions and polar particles to move through.

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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

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Remember!

• In diffusion-particles (solutes) move from an
  area of HIGH concentration to LOW In osmosis-
  water 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

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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.

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• But what if you needed to move particles against
  their concentration gradient?

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Active Transport

• Transport proteins use ________to move particles
  against their concentration gradient, from a low
  concentration to a high concentration.

energy
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Sodium-Potassium Pump

• Carrier- protein that pumps 3 sodium ions
  (Na)________ the cell, while pumping
  2 potassium ions (K)________.

outside
inside
http//highered.mcgraw-hill.com/sites/0072495855/s
tudent_view0/chapter2/animation__how_the_sodium_po
tassium_pump_works.html
http//www.brookscole.com/chemistry_d/templates/st
udent_resources/shared_resources/animations/ion_pu
mp/ionpump.html
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• 3 Na ions from inside the cell bind to the pump
  protein. Energy from ATP is added to the protein.
• The Na ions are moved to the outside of the
  cell.
• The 3 Na ions are released and 2 K ions bind to
  the protein.
• The protein changes back and releases the 2 K
  ions into the cell.

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Vesicle Mediated Transport

• The fluid plasma membrane can pinch off
  forming vesicles that can move very
  _______particles or lots of ______particles.
• This process needs _______.

large
small
energy
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Endocytosis

• Outside materials are brought __________ the
  cell.

inside
3) Vesicle with food
1) Food particle
2) Pouch forming around food
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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.

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Exocytosis

• Material from inside the cell is released
  _________ by vesicles.

outside
1) Vesicle fuses with membrane
3) Particle released
2) Pouch opens