Download Ch 5 Homeostasis and cell transport

CH 5
HOMEOSTASIS
AND CELL TRANSPORT
How do cells get the things they need?
 How do they get rid of their wastes?
 How do cells transport stuff?
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5-1 Passive transport
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Materials must be able to cross the cell membrane
Some don’t require energy input: Passive transport
Diffusion: movement of particles from area of high
to low concentration
Diffusion
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Two solutions can have different concentrations of
solute (particles)
Concentration gradient: the difference in
concentration of molecules
Diffusion driven by kinetic energy
 Molecules
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are in constant motion
Diffusion occurs until equilibrium is reached
Diffusion across membranes
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Diffusion across a membrane is called simple
diffusion
Not everything can diffuse through a membrane
Limits include
 Size
 Polarity
Osmosis
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Osmosis: process by which water molecules diffuse
across a membrane from an area of high to low
concentration
Form of passive transport
Direction of movement depends on relative
concentration of solutes in solution
Direction of osmosis
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If concentration of solutes outside of cell is lower than
inside the cell, the solution outside is hypotonic
 Water
diffuses into cell
 Animal cells can lyse (burst)
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If concentration of solutes outside the cell is higher
than inside, the solution outside is hypertonic
 Water
diffuses out of cell
 Plasmolysis (cell shrinks)
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When concentrations are equal: isotonic
 Equal
movement into and out of the cell
Animal Cells (red blood cells)
Plant cells
More osmosis stuff
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Turgor pressure: pressure that water exerts against
plant cell wall
Page 99: contractile vacuoles: remove excess water
`http://www.youtube.com/watch?v=9Ynm5ZOW59
Q
Facilitated diffusion
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Passive diffusion
Molecules cross cell membrane through transport
proteins
Active transport
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Movement of
substances from low
to high concentrations
Against the
concentration
gradient
Requires energy
Types of active diffusion
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Endocytosis and Exocytosis
http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapter5
/endocytosis_and_exocytosis.html http://www.youtube.com/watch?v=K7yku3sa4Y8
Types of active diffusion
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1.
2.
3.
4.
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Endocytosis: fluid, macromolecules, or other large
particles brought into cell
Pouch forms in membrane lipids
Materials fill pouch
Pouch pinches in and breaks off from membrane
Now a vesicle
Two types:
Pinocytosis: transport of fluids (“cell drinking”)
Phagocytosis: large particle transport (“cell eating”)
http://www.youtube.com/watch?v=pvOz4V699gk&featur
e=fvwrel
Exocytosis
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Process by which a substance is released by a cell
http://www.youtube.com/watch?v=U9pvm_4-bHg