ap biology the cell membrane ap biology overview the cell membrane separates the inside of a living...
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AP Biology
The Cell Membrane
AP Biology
Overview The cell membrane separates the inside of a
living cell from its surroundings Function to maintain the homeostasis of the cell
The cell membrane is selectively permeable. allows some substances to cross more easily
than others, and some not at all.
Made primarily of phospholipids, with proteins & other macromolecules throughout.
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Phospholipids
Fatty acid
Phosphate
Fatty acid tails hydrophobic
Phosphate group head hydrophilic
Arranged as a bilayer
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Phospholipid bilayer
polarhydrophilic
heads
nonpolarhydrophobic
tails
polarhydrophilic
heads
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In and Out Reminder: It is selectively permeable. Only certain things can pass through
the phospholipid bilayer: Pass through easily
Small, non-polar (hydrophobic) substances Ex: CO2 and O2
Do not pass through easily Polar (hydrophilic) substances Ex: Water, Sugar, Ions Large molecules
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More than lipids… Membrane proteins are
inserted into the phospholipid bilayer
Fluid Mosaic Model Fluid
flow Mosaic
made of smaller partsIt’s like a fluid…It’s like a mosaic…
It’s the Fluid Mosaic Model!
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Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer
Extracellular fluid
Cholesterol
Cytoplasm
Glycolipid
Transmembraneproteins
Filaments ofcytoskeleton
Peripheralprotein
Glycoprotein
Phospholipids
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Membrane Proteins Proteins determine membrane’s specific functions
cell membrane have unique collections of proteins
Membrane proteins: peripheral proteins
loosely bound to surface of membrane cell surface identity marker
integral proteins penetrate lipid bilayer transmembrane protein go all the way through transport proteins
Channels and pumps
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NH2
H+
COOH
Cytoplasm
Retinalchromophore
Nonpolar(hydrophobic)-helices in thecell membrane H+
Porin monomer
-pleated sheets
Bacterialoutermembrane
proton pump channel in photosynthetic bacteria
water channel in bacteria
Examples
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Many Functions of Membrane Proteins
Outside
Plasmamembrane
InsideTransporter Cell surface
receptorEnzymeactivity
Cell surface identity marker
Attachment to thecytoskeleton
Cell adhesion
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Any Questions??