Download SC B- 2.5: Explain how active, passive, and facilitated

Honors Biology
Chapter 7Section 3
Cell Boundaries


surround all cells
is a thin, flexible barrier that acts like the
cell’s “gate keeper”
 made of lipid-bilayer
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provides protection & support
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Fluid Mosaic Model
 phospholipids

resembles an ever-moving sea of fluid
lipids that has large proteins bobbing
along throughout the lipids
Phospholipids (~70% of membrane)
Cholesterol:
1.
2.

changes fluidity of membrane
Glycolipids
3.

sugar molecule on lipid
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Integral Proteins
 go all the way thru the membrane
 channel proteins
 receptor proteins

Peripheral Proteins
 on inside or outside of membrane
 +/- attached to integral proteins

found in:
 plant cells
 fungi cells
 algae
 bacteria


secreted by cell membrane
allow O2, CO2, glucose, & H2O to pass
through
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all cells bathed in liquid
solutes dissolve in solvent (water)
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concentration:

 mass of the solute /vol of solution
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does not require cell to spend energy to move
substances
substances moving from area where it is in
higher concentration  area where it is in
lower concentration
1.
2.
3.
simple diffusion
osmosis
facilitated diffusion
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
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all particles have KE
due to the KE of particles they will move about
until they are evenly distributed in the space
they occupy
what we see is particles moving from where
they are in high concentration  where they
are in lower concentration

a form of passive transport
 cell not spending nrg to make it happen

movement of particles continues even after
equilibrium reached


when concentration of solutes equal thru out a
system
since solute particles still moving it is also
referred to as dynamic equilibrium

http://highered.mcgrawhill.com/sites/0072495855/student_view0/cha
pter2/animation__how_diffusion_works.html
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is the diffusion of water across a
semi-permeable membrane
it‘s water moving from where water is in high
concentration  water is in lower
concentration

semi-permeable = selectively permeable
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Predict what will happen
in the container on
other side
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water will move down its concentration gradient
until equilibrium is reached

when concentrations of solutes same on both
sides of membranes : equilibrium reached
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cells are in isotonic solutions when the
concentration of solutes inside cell =
concentration of solutes outside cell

for human cells isotonic soultions = 0.9% NaCl
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“above strength”
cells in ECF (extracellular fluid) with a higher
concentration of solutes than inside cell
water in higher concentration inside cell so
water leaves cell by osmosis…..cell
shrinks….called crenation

called plasmolysis


“below strength”
water now in higher concentration in ECF so
water will move from outside cell  inside
cell…. cell swells and eventually pops….. called
hemolysis if it is a RBC, other cells it is called:
cytolysis

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some substances move in/out of cells by
diffusion but require a transport protein to
cross the cell membrane
substance still moving from side with higher
concentration  side with lower concentration
example: sugars move into cells by facilitated
diffusion

http://programs.northlandcollege.edu/biolog
y/Biology1111/animations/passive3.swf

moving substances in/out of cell that requires
cells to spend energy (usually in form of ATP)
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substances are moving against their
concentration gradients (from where they are in
low concentration  high concentration)
1.
2.
3.
Pumps
Endocytosis
Exocytosis
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protein in cell membrane that “pumps” ion or
molecule in/out of cell against its concentration
gradient
most pumps use ATP as source of energy
most important pump is Na+/K+/ATPase
pump

http://www.brookscole.com/chemistry_d/te
mplates/student_resources/shared_resources
/animations/ion_pump/ionpump.html
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process of cell taking up material into cell by
means of infolding pockets of cell membrane

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cell “eating”
done by unicellular organisms and phagocytes
in multicellular organisms
 macrophages
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cell “drinking”
cells take up liquid from surroundings
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when cells need to expel larger amounts of
materials than can be expelled thru transport
protein
storage vacuole moves to cell membrane; its
membrane fuses with cell membrane expelling
contents into ECF
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endocytosis is removing some membrane from
cell membrane
exocytosis is adding some membrane to cell
membrane
usually evens out