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13 Cards in this Set
- Front
- Back
Fxns of Plasma Membrane
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1. outer boundary of cell
2. barrier/regulation of passage of molecules 3. mediated interaction bw cell & environment (keeps mem. potential) |
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Plasma Membrane Structure
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-phospholipid bilayer associated w/ different proteins, glycolipids, & cholesterol
-4 major phospholipids 2 outer = sphingomyelin & phosphatidylcholine 2 inner = phosphatidylserine & phosphatidylethanolamine (somtimes phosphatidylinositol) |
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Role of Cholesterol
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-temperature dependent
fxn @ high temp: -makes membrane less fluid -reduce its permeability -keeps mem together (specifically @ hydrophobic areas like wax) fxn @ low temp: -maintains mem fluidity (increase) |
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Membrane Proteins
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-lipids are structure of membrane
-proteins responsible for fxn types: -peripheral: indirectly associated, can be released w/out disrupting membrane -integral: protein w/in lipid bilayer -only released after disrupting membrane (solubolize mem w/ detergent) |
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What percentage of Plasma Membrane protein?
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~50% (can be as much as 80%)
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Integral Proteins
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-span the membrane
-number of membrane domains vary: -Glycophorin: passes once -Band 3: passes multiple times thru membrane -G-linked protein: passes thru 7x |
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Other Membrane Proteins
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1. GPI anchored: linked to outer membrane
2. associate w/ inner: via lipid attach, +/- charge, disulfide bonds |
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Transport of Small Molecules
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-passive diffusion
-ex: ethanol, O2, CO2, benzene -small hydrophobic molecules -high to low concentration gradient -no membrane proteins involved |
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Facilitated Diffusion
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-move along concentration gradient high to low
-involves membrane proteins -charged molecules & other large molecules can enter cells ex: glucose, aa, ions |
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Active Transport
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-moves against concentration gradient
-input of energy (ATP hydrolysis) -pumps -ex: NA-K pump |
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Ion Gradient & Active Transport
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-in GI tract, glucose moves against concentration gradient
-does not utilize ATP -utilizes Na gradient established by Na-K pump -free-ride w/ 2 Na coming in cell |
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Epithelial Glucose Transport
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-intestinal epith. transport glucose against concentration gradient
-then release glucose into blood w/ conc. gradient -apical and basal domain separated by tight jxns |
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1. Glucose into cell:
2. Fxn of Tight Jxn 3. Glucose into Bloodstream |
1. via Na/K pump - sodium gradient *only on apical
2. separates 2 proteins from one another, keeps unidirectional flow of glucose 3. facilitated diffusion |