Transcript CH 8: Cellular Transport

CH 8:
Cellular Transport
Diffusion and Osmosis
What is diffusion?
- the movement of molecules from regions of high
concentration to regions of low concentration, “down”
a concentration gradient.
What is osmosis?
– The diffusion of water across a selectively
permeable membrane
Why do we need to regulate osmosis?
– To maintain homeostasis because the plasma
membrane is naturally permeable to water
Osmosis
How long does water diffuse in a solution?
- Until it has reached equilibrium (even
distribution)
What controls osmosis?
– The concentration gradient
What is a concentration gradient?
– The unequal distribution of particles
Types of Solutions: Isotonic
Remember: Salt Sucks!!!
"ISO" means the same
Definition: When the
concentration of water is
the same inside and
outside the cell so a cell
remains the same.
Both animal and plant cells
retain normal shape and
pressure
Types of Solutions: Hypotonic
• The prefix "HYPO" means less
-Less water inside the cell than outside so water will
move into the cell.
• Definition: When the concentration of water is lower
inside the cell than outside the cell so the cell swells
• What happens: The cell swells up
• Animal Cell- swell until they burst
• Plant Cell- swell beyond their normal size as pressure
increases; this pressure is called turgor pressure.
The plasma membrane presses against the cell wall
and makes the cell more firm (why grocers mist fruits
at the market)
Types of Solution: Hypotonic
Types of Solution: Hypertonic
• The prefix "HYPER" means more
-More water inside the cell than outside so
the water leaves the cell.
• Definition: When the concentration of water
is higher inside the cell than outside the cell
so the cell shrivels
• What happens: Cell shrivels up
• Animal cell- shrivels up
• Plant cell – loses pressure as the plasma
membrane shrinks away from the cell wall; the
plant wilts = plasmolysis
Types of Solution
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm
Red Blood Cells in Solution
Burst---------------Swollen----------Normal-----------------Plasmolysis---------
• http://www.wiley.com/college/boyer/0470003790/animations/m
embrane_transport/membrane_transport.htm
• http://www.northland.cc.mn.us/biology/Biology1111/animations/t
ransport1.html
Passive Transport:
No Energy Required
• Passive Transport -the movement of
particles across a membrane that goes with
the concentration gradient…high
concentration low concentration…and
energy is not required
• What do materials need to cross the plasma
membrane? Transport proteins
• What is this process called?
Facilitated diffusion
Types of Transport Proteins
• Channel Proteins- form channels that
allow specific molecules to flow through.
• Carrier Proteins - change shape to allow
a substance to pass through the plasma
membrane.
Active Transport:
Requires Energy
• Active Transport – Movement of particles
through a membrane against a concentration
gradient…low concentration high
concentration…Energy is required
• How does active transport occur?
A carrier protein binds with the substance to
be transported. The protein changes shape so
that the particle can be released into the
cell--like the opening of a door.
Type of
Transport
Transport
Protein Used?
Direction of
Movement
Requires
energy from
the cell?
Classification
of transport
Simple
Diffusion
No
With
Concentration
Gradient
No
Passive
Facilitated
Diffusion
Yes- channel
protein or
carrier
protein
With
Concentration
Gradient
No
Passive
Active
Transport
Yes- carrier
protein
Against
Concentration
Gradient
Yes
Active
Passive Transport vs. Active
Transport
Transport of Large Particles
• Endocytosis- The process
by which a cell surrounds
and takes in material from
its environment
• Explain the process of
endocytosisthe material is engulfed and
enclosed by a portion of the
cells plasma membrane.
Transport of Large Particles
• Phagocytosis- the
engulfing and
ingesting of solid
particles- “cell
eating”
• Pinocytosis- the
ingestion of fluid
into a cell- “cell
drinking”
http://www.researchandteaching.bio.uci.
edu/lectureprojects.html
Exocytosis
• Exocytosis- the expels or secretes
materials from a cell.