Download Plasma Membrane ppt

Plasma Membrane
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Made of 2 groups of organic
molecules: phospholipids
and proteins
Phospholipids: molecules
shaped like a head with 2
tails
Heads are the phosphorous
group which are polar
(attract H2O)
Tails are long lipid chains
that are non-polar (push
H2O away)
Polarity of the phospholipids
causes them to form a 2
layer “sandwich” with the
heads outside and wet and
the tails inside and dry
Prevents most materials
from passing in/out of cell
PM
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Proteins are
embedded in the
bilayer
3 types: Marker
proteins (curley-q)
identify the cell as
to type
Receptor proteins
gather info about
the cell’s
surroundings
Channel proteins
act as the
“gatekeeper” of the
cell allowing larger
molecules in/out of
the cell
Passive & Active Transport: Moving
Materials across the Plasma
Membrane
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First a chemistry
review:
Solute is the substance
that dissolves in
another substance
Solvent is the more
plentiful substance that
dissolves the solute
Mixture of solute and
solvent= solution
Passive Transport
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Does NOT involve the use of E to bring things
in/out of cell
Molecules seek homeostasis between the
inside/outside of cell using the concentration
gradient
Diffusion: when substances move from an area of
higher concentration to an area of lower conc.
Example: O2 in your blood stream
Osmosis: diffusion of H2O molecules in the direction
of higher solute conc. (if solute is high then H2O is
low)
P M and 3 solutions
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Hypertonic solution: solute conc. Out of the
cell is higher than in the cell (more H2O
molecules in the cell)
H2O molecules rush out of the cell to area of
lower H2O conc.
Causes cell to shrivel
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Hypotonic solution: solute conc. out of the
cell is lower than in the cell (more H2O out
of cell)
H2O molecules rush into the cell
Cell swells and can explode!
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Isotonic solution: solute conc. is the same
inside of the cell as outside of the cell
Equal amounts leave/enter the cell to
create homeostasis
Cell stays the same size
This is what they give you in an IV to
rehydrate you
One more thing about
diffusion……….
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Facilitated diffusion is when the plasma
membrane is selectively permeable—it is
choosy about what it lets into the cell
Channel protein does the choosing
“Regular” diffusion and osmosis do not involve
the channel proteins
Still does not use E
Active Transport
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Cell uses E to actively bring substances
into the cell against the concentration
gradient
Doesn’t matter if there is MORE of that
substance in the cell—if the cell wants
more it uses E to get more!
Plants use proton pumps to pump H atoms that
are missing their electrons (hence the name )
through the internal membranes of
mitochondria and chloroplasts for E production
(Krebs cycle)
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Animals use sodium-potassium pumps to pump
Na out of the cell and K into the cell
Na bonds with a glucose molecule while it is
outside and then is pumped back into the cell
Glucose is released inside the cell and then Na
leaves on another trip through the pumps
Nerve cells use the differences in Na and K
conc. Caused by these pumps to send signals
across the synapses thru-out the body
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When food particles are too big to
be brought thru the channel
proteins, the cell will engulf the
particle
This is called endocytosis
Pinocytosis is when a liquid w/
dissolved molecules are brought in
Exocytosis is how wastes are
discharged from the cell in
vacuoles; can also secrete
chemical products (hormones)
Phagocytosis is when another
cell or part of a cell is brought in;
WBC “eat” invading bacteria, or
amoebas devour their prey in this
manner