Transcript Types of Transport Across Cell Membranes

Types of Transport Across
Cell Membranes
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Passive Transport
▪ Does not require energy
▪ Substances move from high to low
▪Solutes move down the concentration
gradient
▪Examples: oxygen, water, carbon
dioxide
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Types of Passive Transport
3
Diffusion
▪Movement of
substances
(except water)
across a cell
membrane
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Diffusion of Liquids
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Osmosis
▪ Diffusion of water
Diffusion across a membrane
across a membrane
▪ Moves from HIGH
water
concentration (low
solute) to LOW
water
concentration
(high solute)
Semipermeable
membrane
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Diffusion of H2O Across A
Membrane
▪High water
potential = low
solute
concentration
▪Low water
potential = low
solute
concentration
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3 Types of solutions
▪Isotonic
▪Hypotonic
▪Hypertonic
▪THINK IN TERMS OF SOLUTE
CONCENTRATION NOT WATER
CONCENTRATION!!!!
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Cell in Isotonic Solution
10% NaCL
90% H2O
ENVIRONMENT
CELL
10% NaCL
90% H2O
equilibrium
The cell is at _______________.
NO NET
MOVEMENT
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Cell in Hypotonic Solution
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water
movement?
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Cell in Hypertonic Solution
15% NaCL
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water
movement?
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Ways to Remember Solutions
▪ “SALT SUCKS”
▪ Water wants to join the party
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Think about it:
▪
Why do you cook onions
before you salt them?
▪Why did pioneers use salt to
cure their meats (remember
no refrigerators)
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Cytolysis & Plasmolysis
▪Cytolysis –
Cells swell and burst
▪Plasmolysis –
Cells shrink and
shrivel
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Osmosis in Red Blood Cells
Isotonic
Hypotonic
Hypertonic
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hypotonic
hypertonic
isotonic
hypertonic
isotonic
hypotonic
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Facilitated Diffusion
▪Doesn’t require energy
▪Uses transport proteins to
move material from a high to
low concentration
▪Examples: Glucose or amino
acids moving from blood into
a cell.
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Proteins Are Critical to
Membrane Function
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Types of Transport Proteins
▪ Channel proteins are embedded
in the cell membrane & have a
pore for materials to cross
▪ Carrier proteins can change
shape to move material from
one side of the membrane to the
other
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Channel Proteins
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Carrier Proteins
▪ Carrier proteins
change shape to
move materials
across the cell
membrane
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Active Transport
▪Requires energy or ATP
▪Moves materials from
LOW to HIGH
concentration
▪AGAINST concentration
gradient
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Active transport Example
▪Sodium/ Potassium pump
▪Pumping Na+ (sodium ions) out and
K+ (potassium ions) in against
strong concentration gradients.
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Sodium-Potassium Pump
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Types of Active Transport
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Exocytosis
▪Molecules
moved out of
the cell
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Exocytosis
Exocytic
vesicle
immediately
after fusion
with plasma
membrane.
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Endocytosis
▪Molecules
moved into of
the cell
▪2 types
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Pinocytosis
▪Most common
form
▪Moves dissolved
molecules into
cell
▪Cell “drinking”
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Example of Pinocytosis
pinocytic vesicles forming
mature transport vesicle
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Transport across a capillary cell (blue).
Phagocytosis
▪Used to engulf
large molecules
to bring into cell
▪Cell “eating”
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Phagocytosis About to Occur
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Phagocytosis
- Capture
of a Yeast
Cell (yellow)
by
Membrane
Extensions
of an
Immune
System Cell
(blue)
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