Cellular Transport
Diffusion
Osmosis
Facilitated Diffusion
Active Transport
Filtration
Passive Transport
• NO ENERGY REQUIRED to move
substances across membrane -- water,
lipids, and other lipid soluble substances.
• Types:
–
–
–
–
Diffusion
Osmosis
Facilitated Diffusion
Filtration
Diffusion
• Occurs because of Brownian Motion, i.e.,
the random movement of particles.
• Net movement of particles from an area
of greater concentration to an area of
lesser concentration.
– Concentration gradient, i.e., the
difference in concentration across space.
Diffusion
Molecules move down the concentration gradient
until there are equal numbers of molecules on both
sides ~ dynamic equilibrium.
Dynamic Equilibrium
Molecules continue to move randomly because of
Brownian motion, but there is no net movement.
Osmosis
• Diffusion of water from an area of
greater concentration of water to an
area of lesser concentration of water
-- across a semipermeable membrane.
• Isotonic Solutions
• Hypertonic Solutions
• Hypotonic Solutions
Isotonic Solution
• Concentration of solutes in the
solution is the same as inside the cell.
• Cell is in dynamic equilibrium, i.e., no
net gain or loss of water.
H20
H20
Hypotonic Solution
• Concentration of solutes is lower in
solution than inside cell.
• Net movement of water will be INTO
the cell.
H20
H20
H20
Hypotonic Solution
Turgor Pressure -- This is why
grocery stores spray vegetables -crispness!
Plant Cell
Cytolysis -- Animal cell bursts.
Animal Cell
Hypotonic Solutions
Hypertonic Solution
• Concentration of solutes is greater in
solution than inside cell.
• Net movement of water will be OUT
OF the cell.
H20
H20
H20
Hypertonic Solutions
• Meat placed in salt water loses moisture and
is dry and tough when cooked.
• Plant cells placed in salt water shrink,
losing turgor pressure ~ plasmolysis.
• Blood cells in hypertonic solutions will lose
liquid ~ plasmolysis.
Facilitated Diffusion
• Movement across the membrane with the help of
transport proteins .
– Types:
• Carrier protein - its shape fits certain molecules.
• Channel protein - molecules diffuse through channel.
Active Transport
• Transport of materials against (low
to high) a concentration gradient
– REQUIRES ENERGY!
• Large Molecules:
– Endocytosis/Exocytosis
• Molecule engulfed by portion of membrane.
• Portion breaks off as vacuole inside cell.
• Liquid = Pinocytosis
• Solids = Phagocytosis
Active Transport
• Sodium-Potassium Pump
– transports sodium ions out of cell,
potassium ions into cell.
High Potassium
K+
Na+
Low Sodium
High Sodium
Low Potassium
Review
• Types of Cellular Transport
– Diffusion: Movement of solute (high to low)
– Osmosis: Movement of water (high to low)
• Hypotonic, Isotonic, and Hypertonic
– Facilitated Diffusion: Carrier and channel
proteins; Does not require energy
– Filtration
– Active Transport -- Requires energy
• Endocytosis, Pinocytosis, Phagocytosis, Exocytosis,
Some Carrier Molecules (Sodium-Potassium Pump)