week 3 329
U of L
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This 4 page Class Notes was uploaded by Mary-elizabeth Notetaker on Friday September 9, 2016. The Class Notes belongs to Bio 329 at University of Louisville taught by Paul Himes in Fall 2016. Since its upload, it has received 9 views. For similar materials see Cellular Molecular Biology in Biology at University of Louisville.
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Date Created: 09/09/16
Week 3 Tuesday, September 6, 2016 3:23 PM amphipathic-has both polar and nonpolar end Amphoteric-act as buffer,can be acid or base -nucleic acid polymers ATP- cells E currency Short term storage & E transfer 10s worth of E in our cells Glycogen/starch- medium term storage Fats/triglycerides- long term storage High E bonds- like charges repel..phosphates(-) don’t like to be by each other E given off when stress relieved ATP---> ADP + P ….releases E Bio membranes • Bio mols ○ Lipids- diverse group of NP mols Triacylglycerol(triglycerides) □ Glycerol-->esterbond-->3fatty acids(Fas) FAs- unbranched hydrocarbons w carboxy, group… amphipathic ◊ Saturated- all C have 2 H's, no dbl bonds, packed tight Solid at room temp Fats & waxes ◊ Unsat- one or more C=C, kin, not tight Liquid at room temp Oils ◊ Trans fats get made from adding H back to unsat fats and cis dbl bonds turn to trans dbl bonds □ More E dense…better for E storage Membrane lipids: □ Phosphoglycerides- phosphate group and something else(polar head group) on glycerol w FA Diglyceride- 2 fatty acid on glycerol Functional head group- choline, serine, ethanolamine, inositol □ Sphingolipids- ceramines Formed by attachment of sphingosine to FAs Includes glycolipids- imp for neural connections □ Cholesterol- smaller and less amphipathic 4 C rings Precursor for steroid hormones Change fluidity of membrane ◊ Shape blocks flow of lipid tails Small OH head out, rest of mol in membrane Only in animal membranes- similar compounds in other orgs Stx/fx of membrane lipids • Plasma membrane- outer cell boundary ○ Various lipids Macromol not formed by polymerization Msinly phospholipids Also sph ○ Characteristic trilaminar appearance(3 layers).. Shared by all cell types Strain binds polar head groups Phobic tails unstained • Membrane fxs ○ Compartmentalization- sheets enclosing intracellular compartments Separate inside/outside ○ Scaffold for biochem activities- organizes enzymes for effective intx Keep things together Couple rxs ○ Selectively permeable barrier- allow regulated exchange ○ Transport solutes- move subs btwn compartments Pores…membrane proteins Respond to external signals- signal transduction Bio 329 Page 1 ○ Respond to external signals- signal transduction ○ Intracellular rx- mediate recog & intx btwn adj cells ○ E transduction: chem E->ATP • Nature of membrane ○ Like dissolves like Membrane dissolving power like that of oil ○ Amphipathic ○ Lipid bilayer 2:1 ration lipid to cell SA Leaflet oriented heads out, tails in…lowest E state Influences membrane protein actvity, phys state, solubility of certain mold Formation of continuous sheet--> allows splitting ○ Fluid mosaic model- core lipid bilayer in fluid state, can move □ Membrane proteins form mosaic of particles penetrating lipids Nonuniform- lipids drafts and other groupings Lipids and proteins bound w non-covalent bonds- role for NP side chains Membs have carbs Protein/lipid ratios vary among membrane types-depends on fx Membs of thermophyllic archae may be monoloayers/have ether linkages ○ Membrane lipid comp of specific membranes Composition--> fx □ Nature of head group □ Type of FA tail Allow membs to: fuse, make networks, separate charge Lipid bilayers assemble in sol… liposome □ Vehicle for transport of things to specific body parts □ Antibody targets liposome to specific cell type □ Then memb fuses w cell memb & delivers: Aqueous drug needed inside cell Lipid sol drugs Small mols Other things you want targeted not destroyed/metabolized Asymm of membrane lipids □ Inner/outer memb-> diff compositions Diff intxs & diff physio-chem props Memb lipids move easy in leaflet but rarely flip flop bc act as indep monolayers ◊ PC(outside): helps in reception of signals ◊ PE(outside): imp for curvature ◊ PS(inside): intx w protein…. Flips to Outside to mark old cells • Membrane carbs: 2-10% membrane mass… 90% glycoproteins…rest glycolipids ○ All on excellular surface- away from cytoplasm or outside cell ○ Glycoporteins- short branched oligosaccs(10-15sugars..same or diff) Intxs w other cells and stxs outside cell ○ Glycolipids- monosaccsto short clusters Cell to cell recog sites Blood-group antigens • Membrane proteins- attach asymm to bilayer….. Give membrane sidedness-lipid variation ○ 3 classes Integral membrane proteins □ 25-30% proteins Rolls: receptors, channels, energetic □ Amphipathic □ Phobic domains anchor them to bilayer… need 20 NP AA to cross membrane □ Phillic regions form fx domains outside- van der waals intx w FA tails Peripheral " "- noncovalently attached □ Soluble □ Both leaflets □ More known about internal ones..inner membrane skeleton GPI-anchored proteins- covalently attached to membrane □ Lipid anchored □ Distinguished by: lipid anchor type & orientation □ Glycophosphatidylinositol- outer leaflet… include receptors PrP^c □ No sugars on lipids on inside of cell Bio 329 Page 2 □ No sugars on lipids on inside of cell Condensation rx can happen btwn charged FA and mol □ Inner leaftlet proteins- anchored to memb lipids by long hydroC chains Prenylation • RBC: ○ Hemolysis- membrane ghosts(pop in low salt sol) • Memb proteins purified, characterized--> SDS-PAGE electrophoresis ○ Denature and separate by size, smallest=furthest ○ Proteins show as bands, intensity matters ○ Peripheral proteins(P's) separate from memb easiest • 2 most abundant Ps: both glycoproteins ○ Band 3- 2 homodimers Exchange Cl- & HCO3- across memb Transport CO2 from bondy Buffers blood More than 12 transmembrane domains ○ Glycophorin A- dimer..16 oligo chains Neg charge-->prevent RBC clustering Docking point for malaria paarasite(plasmodium) • Peripheral Ps- under membrane ○ Spectrin- huge (100Nm) Attached to membrane by ankyrin w noncovalent bonds • Memb lipids & fluididty ○ States: Liquid crystal- most common □ Keep orientation but FA tails rotate Frozen gel- little/no movement ○ Depends on: Temp, lipid composition & saturation, and cholesterol presence(prevents close packing, makes memb less permeable) Unsat fat= lower transition temp… pack looser ○ Fluidity- from P's in memb, growth & assembly • Most orgs T changes w external T…need to keep fluid ○ Remodeling lipid bilayer Denature single bonds in acyl chains- desaturases Shuffling FA btwn phospholipid mols- phospholipidases or acytransferases Changing phospholipids made • Lipid rafts ○ Cholesterol/sphingolipids--> pack close--> highly ordered microdomains ○ Float together thru memb ○ Favorable envir for cell surface receptors & GPI anchored Ps ○ Proteins that work together concentrate here ○ Integral ps organize inner leaflet • Diffusion of memb ps after cell fusion ○ Ps/lipids diffuse freely w/in memb 2 sec to cycle around bac cell for lipids Days to flip memb Cell fusion: virus/polyehyleneglycol • P tracked/labeledby FRAP or SPT ○ P usually random movement but can be directed or immobile ○ Limited intxs w ps, cytosol, extracellular mats ○ Dragged ps w/in memb- some have barriers to lateral diffusion Remove intracellular/extracellulardomain to ID restriction Ex) intra- travel- memb skeleton- peripheral ps □ Extra- rate of travel • Mobility restrictions: Ps & lipids ○ Limited to 1 leaflet ○ Confined for brief periods to certain areas- moved to another and stuck Integral memb ps attached to membs act as fences Disrupt attachment & lipids diffuse freely • Cells of organized tissues--> unequal P distribution ○ Epithelia- p of apical memb distinct from lateral & basal Larger than lipid rafts Whole sides of cell act different Bio 329 Page 3 Whole sides of cell act different • Substance movementacross memb ○ Selectively permeable ○ Net flux: diff btwn influx and efflux ○ Passive or active transport • Energetics of movementof solutes ○ Diff spontaneous movement of materials from high concentration to low ○ Uncharged mols- move down gradient and give off E Higher gradient=more E change= more use Powered by inc in entropy--> equilibrium More outside than in, goes in (& reverse) ○ Electrolyte movement- electrochemical gradient Reason for antiporters ○ Lipid permeability Partition coeff- sol in H2O of NP solvent? Moves easier Size Polar: big polar(slow), charged(don’t move), gas(straight thru) • Diffusion of water thru memb- osmosis Moves to eq Water moves, not solute Hypotonic- more ions out of cell than in, water comes in, cell swells Hypertonic- " " in cell than out, water leaves, cell shrivels Isotonic-same …intestines often change osmotic conds ○ Animals are isotonic ○ Plants have turgor… in hypo If hyper, plasmolysis- cell shrivels & memb pulls from cell wall Bio 329 Page 4
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