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25 Cards in this Set
- Front
- Back
What are the functions of membranes?
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1. Define Boundaries and serve as permeability barriers
2. sits of specific function: glucose phosphatase and ER membrane 3. Regulate transport of solutes (simple, facilitated diffusion; active transport, endo/exo cytosis) 4. Detect and transmit electrical and chemical signals (signal transduction) 5. Mediate cell-to-cell communication (gap junctions) |
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What is the Fluid Mosaic Model?
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Singer and Nicolson: membrane consists of a mosaic of proteins in a fluid lipid layer
Davson and Danielli: membranes also contain proteins (protein-lipid sandwich model Overton and Langmuir: Lipids are important components of membranes Gorter and Grendel: The basis of a membrane structure is a lipid bilayer Robertson: all membranes share a common underlying structure Unwin and Henderson: some membrane proteins contain transmembrane segments updated verson postulates that regions of membranes have proteins and lipids athat are ordered into domains (rafts) |
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What are the classes of lipids found in membranes?
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Phospholipids:
-glycerol based: phosphoglycerides -sphingolipids -4 important ones: Phosphatidylcholine, Phosphatidylethanolamine, Phosphatidylserine, Phosphatidylthreonine Glycolipids: NO phosphate have sugar -cerebrosides (neutral single uncharged sugar) -gangliosides (Tay Sachs) Sterols: -cholesterol (series of rings) |
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What is Cardiolipin?
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component of inner membrane of mitochondria - 20 %
important in ETC patients with anticardiolipin Ab (Antiphospholipid syndrome) can have thrombotic events in mid teens (also called Hughes Syndrome) |
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What is a difference between E coli and a human membrane in variations in phospholipid composition?
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E. Coli has a lot of ethanol amine and very little of everything else
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What are Hopanoids?
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They are in the bacteria plasma membrane
do the same thing for prokaryotes as cholesterol does for us they are sterol like molecules because prokaryotes do not have sterols |
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What happens in Thin-layer chromatography for Lipid Analysis?
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sample spotted onto a hydrophilic stationary phase
placed into mixture of organic solvents (mobile phase) solvent moves up late via capillary action, nonpolar lipids (cholesterol) do not adhere to silicic acid and move further up plate, more polar (phospholipids) move slower |
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What are some basic features of FA?
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between 12-20 Cs:
-thickness is dictated by chain length of FA required for bilayer stability saturated FA unsaturated FA: -found in Cis -do not pack tightly due to structural "kinks" |
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What is Membrane Asymmetry?
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Phosphatidylethanolamine, phosphatidylinositol, and phosphatidylserine more abundant in inner-monolayer (Some Enter Innermembrane)
-involved in signal transduction Glycolipids and glycoproteins found in outermembrane - charged asymmetry caused by phospholipid translocators or flippases |
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What are the 3 types of movement in the Lipid Bilayer?
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Transverse diffusion (rare) - flip flop
Lateral diffusion (rapid) Rotation |
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What is evidence for the lipid bilayer's fluid property?
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Fluorescence recovery after photobleaching (FRAP)
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What is characteristic of Transition temperatures in FA?
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long chain FA have higher Tm than shorter chain
unsaturated FA have lower Tm and more fluid |
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What is Cholesterol's effect on Membrane fluidity?
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Cholesterol makes the membranes less fluid at higher temperatures and increases fluidity at lower temperatures (prevent FA chains from getting closer)
Sterols decrease permeability of a lipid billayer to ions and small molecules (better barrier and insulator) |
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What is Homeoviscous adaptation?
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way for organism to regulate membrane fluidity:
-increase amount of shorter chain FA -increase % of unsaturated FA -increase amount of cholesterol |
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How does cholesterol bind to the phospholipid?
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through a hydrogen bond
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What is a Caveolae?
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a type of lipid raft (sequester proteins involved in cell signaling)
small flask-shaped invaginations of plasma membrane that are coated with caveolin (cholesterol-binding protein) |
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How is freeze-fracture microscopy used for membrane protein analysis?
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frozen sample is given a sharp blow and the resultant fracture follows the plane between the two layers, giving rise to the E (exterior) face and the P (protoplasmic) face
E = inside of outer leaf P = inside of inner leaf |
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What are the 3 types of proteins in membranes?
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Integral membrane proteins:
-single pass or multipass proteins -hydrophobic transmembrane segments -can predict by hydropathy plot ( hydrophillic = -G exergonic, hydrophobic = +G endergonic) ex. glycophorin (single pass in RBC), bacteriordhopsin (multipass), Band 3 protein Peripheral Membrane Proteins: -weak electrostatic forces and hydrogen bonding -lack discrete hydrophobic segments ex. Spectrin, Ankyrin, and Band 4.1 (RBC) Lipid-Anchored Proteins: -covalently linked to lipids in membrane -linked to either FA or isoprene derivative in inner surface -attached to outer surface are linked to Glycosylphosphatidylinositol (GPI) -GPI anchored proteins are made in ER as single-pass proteins, cleaved, then linked to GPI -GPI proteins relased by Phospholipase C |
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What is SDS PAGE?
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polypeptides move down the gel at a rate that is inversely related to size
neutralizes charge to separate by size not charge |
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What is western blot?
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transferring protein from the SDS page gel
ex. CFTR patient, most applicable would be western blot |
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What are restriction enzymes what is its process?
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cut DNA into fragments
highly specific, developed for protection against viral infection cut the viral DNA bacterial DNA is protected so not cut by own restrictive enzymes EcoR1 is a popular restrictive enzyme 1st step: RE recognizes enzyme site on DNA, then cut with each strand 2nd step: cut is palindromic, read same in 5-->3 and 3-->5 direction 3rd step: recognize 4th step: bind 5th step: cut and hydrolyze To digest RE you used gel electrophoresis 1 RE has 2 cutting sites, 2 RE has 3 cutting sites |
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What is sense and antisense RNA?
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mRNA is sense:
-single stranded -read in 5-->3 Antisense: -complementary 3-->5 -blocks translation |
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How are membranes glycosylated?
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N-linked glycosylation (Asparagine)
O-linked glycosylation (Serine, Threonine, Hydroxylysine, Hydroxyproline) Most common sugars (carbs): galactose, mannose, N-acetylglucosamine, and sialic acid Lectins: proteins that bind specific sugar groups very tightly - useful for sugar determination |
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What is the Glycocalyx?
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the surface coat of carbohydrates extending from glycoproteins and glycolipids
fuction to protein microvilli of intestine |
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What are examples to prove that membrane proteins vary in their mobility?
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expermental evidence of protein mobility:
-cell fusion experiments -freeze fracture experiments of membrane exposed to an electric field experimental evidence of restricted mobility: -photobleaching mechanisms of restricting protein mobility: -tight junctions -anchoring proteins -polarized cells: membrane proteins are restricted to a specific part of the cell membrane USE Polyethylene glycol for Mouse |