Types of Transport Across Cell Membranes

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Types of Transport Across Cell Membranes
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Simple Diffusion

• Requires NO energy, passive movement
• Molecules move from area of HIGH to LOW
  concentration
• Random movement
• of particles
• Brownian Movement

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Diffusion of Liquids
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Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to
LOW)
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Osmosis

• Diffusion of WATER across a membrane
• Moves from HIGH water concentration to LOW water
  concentration

Diffusion across a membrane
Semipermeable membrane
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Three types of conditions

• Isotonic solutions
• When the amount of solutes is equal inside and
  outside of cell (cell will stay the same)
• Hypotonic solution
• When solutes outside are lower than inside cell
  (cell will swell) more water outside
• Hypertonic solution
• When solutes outside are higher than inside cell
  (cell will shrink) more water inside cell

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Cell in Isotonic Solution
10 NaCL90 H2O
ENVIRONMENT
CELL
NO NET MOVEMENT
10 NaCL 90 H2O
What is the direction of water movement?
equilibrium
The cell is at _______________.
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Cell in Hypotonic Solution
10 NaCL90 H2O
CELL
H2O
20 NaCL 80 H2O
What is the direction of water movement?
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Cell in Hypertonic Solution
15 NaCL85 H2O
ENVIRONMENT
CELL
H2O
5 NaCL 95 H2O
What is the direction of water movement?
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Cells in Solutions
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Isotonic Solution
Hypotonic Solution
Hypertonic Solution
NO NET MOVEMENT OF H2O (equal amounts entering
leaving)
CYTOLYSIS
PLASMOLYSIS
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Osmosis in Red Blood Cells
Isotonic
Hypertonic
Hypotonic
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Hypertonic
Isotonic
Hypotonic
Isotonic
Hypertonic
Hypotonic
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Moving Things in and out of Cells

• Cellular Transport

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A.Passive Transport (2 types)

• 1.Simple Diffusion
• Doesnt require energy
• Moves high to low concentration (Down)
• Example Oxygen or water diffusing into a cell
  and carbon dioxide diffusing out.

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• 2. Facilitated diffusion
• Doesnt require energy
• Uses transport proteins to move high to low
  concentration
• Examples Glucose or amino acids moving from
  blood into a cell.

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2.Facilitated Diffusion
Molecules will randomly move through the pores in
Channel Proteins.
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2.Facilitated Diffusion

• Some Carrier proteins do not extend through the
  membrane.
• They bond and drag molecules through the lipid
  bilayer and release them on the opposite side.

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B.Active Transport

• Requires energy or ATP
• Moves materials from LOW to HIGH concentration
• AGAINST (up) concentration gradient

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Sodium-Potassium Pump
3 Na pumped in for every 2 K pumped out
creates a membrane potential
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1. Endocytosis Moving the Big Stuff
Large molecules move materials into the cell by.
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Endocytosis

• Cell forms an invagination
• Materials dissolve in water to be brought into
  cell
• Called Cell Drinking

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2.Exocytosis The opposite of endocytosis is
exocytosis. Large molecules that are manufactured
in the cell are released out of the cell through
the cell membrane.
Inside Cell
Cell environment
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Exocytosis