BIOMG 1350 1st Edition Lecture 7Outline of Last Lecture I. Cytoskeleton and Motor FilamentsOutline of Current Lecture II.Membrane StructureIII. Membrane Lipids: provide selective barrierIV. Membrane ProteinsCurrent Lecture- The endoplasmic reticulum is concentrated by kinesin, while the Golgi is concentrated bydynein - Membrane Structure:o Enclose a cell, selective barrier called plasma membrane. It is the interface the cell has with its environment. Plasma membrane: receives info, sends signals, capacity for movement and expansion, import and export of moleculeso Prokaryotes vs. Eukaryoteso Lipid bilayer on plasma membrane: 5nm First model called “fluid mosaic model” or a “sea of lipids” Experiment to test protein mobility: FRAP: bleach and recovery. It they recover quickly it is very dynamic, if it doesn’t it means they aren’t very dynamic- Membrane Lipids:o Amphipathic: hydrophilic head and hydrophobic tailo Most abundant lipids in membrane are phospholipids Have head group and two long hydrocarbon tailso Structure: 18 carbons long Saturated is straight and un saturated is double bond and has a kink All have a phosphate that has a charge Head group has positive charge Extremely asymmetric Glycolipids always on outside of cell Inside has a negative net chargeThese 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.o Examples: Glycolipid: sugar molecule on lipid, sugar loving Cholesterol: amphipathic- Stiffens membrane, fills up the gaps that kinko They form lipid bilayers in water: shield hydrophobic tails from water They spontaneously form into this!o The phospholipid bilayer form a liposome: all head groups are facing water (in a circle)o Lipid fluidity increases with increasing proportion of unsaturated hydrocarbon tails. Fatty acid chains in an unsaturated molecule have kinks, and it prevents them from going close together. Shortening them makes it more fluid as wello Lipids can move around in he plane of the membrane Flip-fop (rarely in a pure lipid bilayer), flexion, rotation, lateral diffusion “Flippases” flip them from one side to another creating asymmetryo Permeability: Small hydrophobic molecules can easily get through lipid bilayer Small uncharged polar molecules can get through membrane Large uncharged polar molecules cant get though membrane Ins can get through cell (they are too charged) Proteins in membrane transport that cannot get across pure lipid bilayer…- Membrane Proteins:o Variety of functionso Transporters: selective transport in/outo Supported by anchors. Examples: connection between two cells. Cell to cell or cell to matrico Receptors receive signals and send them throughout the cello Enzymes embedded in membraneo Each membrane protein must have a specific orientation with respect to the bilayero Can be: Transmembrane, less common, alpha helix. A hydrophilic pore can be formed by multiple transmembrane alpha helices. It turns into a highly selective pre Dip into lipid bilayer but not all the way through Lipid linked Protein attachedo Urea can be used to see if a certain protein is found in the membraneo Peptide chain: usually crosses the bilayer as an alpha helix R groups are hydrophobic: they can sit well with the hydrophobic tailso Lateral mobility of plasma membrane proteins can be restricted in several ways Example: red blood