BIOM 3800 1nd Edition Lecture 4 Outline of Last Lecture I. Membranes, Channels and TransportOutline of Current Lecture I. IntroductionII. Structure/Organization of MembraneA. Plasma MembraneB. Membrane CompositionIII. Crossing MembraneA. DiffusionB. OsmosisIV. Mechanism Transmembrane MovementsA. PressureB. DiffusionC. Active TransportV. Vesicle Membrane TransportA. EndocytosisB. ExocytosisC. PinocytosisD. PhagocytosisVI. Cell to Cell JunctionsVII. CAMSCurrent LectureMembranes, Channels, and TransportsI. IntroductionChapter 4 is discussion of membrane structure and the role it plays in maintain cells stability II. Structure/Organization of MembraneA. Plasma Membrane about 70-100A 100A= 1nm =10x10-9 m These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. Surrounds all animal cells2. In spite of thinness remarkable ability to regulate cells interior environment enough tokeep it stable enough regardless of external environment3. Concentration gradients (Measure of concentrations and how they change from one place to another) are formed across plasma membranes because it manages to keep different concentrations of ions from inside and outside of cell4. Protein structures move substances between compartments within cella. Membrane doesn’t hold cell together by itself cytoskeleton i.e microfilaments, microtubules, sustain cell shapeb. Membrane selectively permeable meaning must have certain channel transport proteins if molecule tries to get across cell and CAN’T get across if water AND soluble moleculesB. Membrane Composition1. Lipid Bilayer (Gorter and Grendel) – All membranes have thema. Lipids/proteins held together noncovalent interactionsb. Fluid structuresc. Basic membrane structure provided by lipidsi. lipid molecule dissolve in organic solvents NOT in waterd. Lipids 3 types in cell membranei. Phosphoglycerides: AKA phospholipids -- glycerol backboneii. Sphingolipids backbone sphingosine bases (don’t know much about so don’t need to know much more about sphingolipids ontest)iii. Sterols:  cholesterol - Phospholipids and sphingolipids amphipathic meaning one in hydrophobic other hydrophilic- Hydrophobic tails have weak van der Waals interactions between them keeping them stabilized also aids in self repair when bilayer torne. Proteins (2types)i. Lipoproteins phophoglycerides attached to proteinsii. Glycoproteins: proteins with sugar attachedf. Hydrophobic tails  low permeability to polar substances  Greater permeability to nonpolar substancesg. Cholesteroli. Insoluble in water requires carrier proteins (HDLP) high density lipoproteins and (LDLP) low density lipoproteins. ii. Cholesterol is a moleculeiii. When talking about bad and good cholesterol in reference to these high density and low density lipoproteinsiv. Good Cholesterol HDL more soluble and better carriersBad Cholesterol LDL associated with arteriosclerosish. Fluid Mosaic Model (Singer and Nicolson)i. Composition from one side of bilayer to other do not “flip-flop”ii. Some protein molecules penetrate bilayer completely others only partially- Hydrophilic portions- protrude from bilayer and interact with water- Hydrophobic portions embedded in bilayer keep proteins stabilized in lipid bilayeriii. Adjacent molecules in monolayer exchange places rapidly (cholesterol plays imp. Role in thisiv. Chemical natureLipidLengths nonpolar tails- All affect membrane interactions with proteins- Structural properties of membraneIII Crossing MembraneA. Diffusion: thermal randomization1. Extremely slow when viewed on a tissue2. Rapid on microscopic scale3. Are of high to low concentration4. Destroys concentration gradients a. Permeability:; rate at which substance passively penetrates membrane under specialset conditionsB. Osmosis: Movement of water down its concentration gradient (kidneys function through osmosis)!!!1. When a membrane is involved creates hydrostatic pressure (fluid mechanical pressure)2. Osmotic pressure is proportional to solute concentration 3. Osmolarity formula= MnαM molarity moles/litersn = # of particlesα= “activity” of dissolved molecule4. Tonicitya. Depends on accumulation of solute in tissuei. Hypotonic solute less on outside of cell than insideii. hypertonic solute more on inside than out iii. isotonic solute concentration same on either side of cell5. Cannot measure osmolarity inside cells6. Sucrose can’t get across membrane whereas urea can with no transporter but slow possible swelling of cell7. Mechanisms that fight this like Na+/K+ pumps keep swelling from occurringa. Electrochemical influences on ion transport as described above dependent oni. chemical influences (conc. gradients)ii. electrical influences (electric field)b. Donnan Equilibrium states that solutes become distribute unevenly throughout cell if membrane impermeable to certain ionsi. ion differences in cells across frog muscle*more Na+ outside of cell* more K+ inside of cell*more Ca++ outside of cell* more Cl- outside of cellIV. Mechanism Transmembrane MovementsA. Pressure *think of a syringe*B. Diffusion1. Osmosis2. Facilitated diffusion or passive transport (can be channel or carrier dependent diffusion3. Dialysis4. Alcohol through membranes5. Uniport help diffusion single solute moleculea. Channels and uniports help molecules go down concentration gradientb. Cotransport symports and anitports and active transport described next help molecule go against concentration gradientC. Active Transporta. 2 types *Primary Active (ATP Powered Transport ….need to know molecule enzyme hydrolizeATP and it does something*Secondary active transport ( Electrical Gradient Transport) i. primary transport responsible for Na+ pump 3 Na out and 2K in maintaining concentration gradientii. secondary transport coupled reactions via symporters and antiporters called COTRANSPORT - symporters molecules move in same direction like Na+ will allow glucose to be transported into the cell along same path- antiporters molecules that need to be transported out leavealongside transport in by Na+V. Vesicle Membrane Transport*Processes described above only work with small polar molecules but not good ways to transport macromolecules the 4 methods below are othersA. Endocytosis: intake of material into cellB. Exocytosis: release of chemicals from cellsC. Pinocytosis: specifically