BMB 462Exam # 1 Study Guide Lectures: 1 - 9Lecture 1 Definition of lipids: molecules that are not soluble in waterLipids do not contain a structural defining feature, like the other biomolecules doDescribe the structural features found in common lipids: A carboxylic (polar) head, a hydrophobic (nonpolar) tail; saturated or unsaturated; typically 12-24 carbon atomsMelting point increases with length of carbon chain and unsaturationCorrectly use fatty acid nomenclature: Common names – these need to be memorizedLauric acid = 12:0 Palmitoleic acid = 16:1 (Δ9)Myristic acid = 14:0 Oleic acid = 18:1 (Δ9)Palmitic acid = 16:0 Linoleic acid = 18:2 (Δ9, 12)Stearic acid = 18:0 α-Linoleic acid = 18:3 (Δ9, 12, 15)Arachidic acid = 20:0 Arachidonic acid = 20:4 (Δ5, 8, 11, 14)Lignoceric acid = 24:0Shorthand carbon skeletons – Chain length:# double bonds (Δbond position)Start counting from the carboxyl groupSystematic names – have to do with the # of Carbons and the # of double bonds (learn the prefixes, i.e. penta = 5)Omega fatty acids – start counting from the omega Carbon, the carbon in the methyl group on the opposite side of the fatty acid from the carboxyl group. The # denotes the 1st carbon with a double bondLecture 2 Predict functions of lipids based on physical and chemical properties:Memorize basic structure of triacylglycerol (glycerol backbone with 3 fatty acids), membrane lipids (glycerophospholipids, sphingolipids, galactolipids/sulfolipids, sterols); the structure of isoprene so you can recognize isoprenoidsIdentify the bonds in lipids that are cleaved by different lipases; know the products:Lipases break down lipids for digestion/lipid turnover/signalingPhospholipase A1 (PLA1) – cleaves between the fatty acid and Carbon 1 of the glycerolPhospholipase A2 (PLA2) – cleaves between the fatty acid and Carbon 2 of the glycerolPhospholipase C (PLC) – cleaves between Carbon 3 of glycerol and phosphatePhospholipase D (PLD) – cleaves between the phosphate and the head groupDiscuss examples of signaling by lipids and the role of NSAIDs in signal disruption:Study the bottom figure on page 12 of “Lipid Structures, Properties, and Functions” for NSAIDs impact on signalingLecture 3 Design an experiment separating a mixture of lipids and identify the components:Lipids are hydrophobic and cannot dissolve in water, which will help separate them from other cellular components (i.e. nucleic acids and proteins), which are polar. i.e. in isolation with organic solvents, lipids will end up in the organic solvent while all other components will filter into the aqueous solutionTo separate the various types of lipids, once lipids have been isolated, use the different polarities in the structures of the lipids to draw them apart, via chromatographyi.e. nonpolar lipid structures will be the first to elute, while polar lipids remain attached to the silica of the filter. Increasing polarity of the wash liquid will elute increasingly polar lipidsMass spectrometry can determine specifically the identities of the lipidsRecognize membrane lipids as amphipathic compounds that form lipid bilayersMembrane lipids are only those lipids that have both hydrophobic and hydrophilic areasDescribe the functions of membranes. How do the components relate to those?Membranes act as barriers, structural support, compartmentalization, transport of nutrients/wasteMore proteins in a membrane indicates the membrane does a lot of activity; i.e. transport of molecules. E. coli has more proteins in the membrane than human myelin sheath b/c the bacterial membrane is a barrier to the environment while the sheath is mainly insulationIdentify the location, orientation, and structures of typical lipids/proteins in the membraneMembranes are asymmetrical; receptor proteins are always oriented outside to receive hormones, glycoproteins also commonly located in the outer leaflet for signaling/cell-cell communicationCommon membrane lipids are sphingolipids, phosphatidylcholine, phosphatidylethanolamineLipoproteins/lipid-linked proteins remain associated with the membrane, so that they can only diffuse around membrane and not through the cellInterpret hydropathy plotsThe x-axis is displayed from the N-terminus to the C-terminus.Nonpolar, hydrophobic portions of alpha-helices in transmembrane proteins shows up as a positive peak on the plotBeta-barrels alternate polar and nonpolar residues so they don’t appear on the plotsLecture 4 Describe the fluid mosaic model. How is fluidity controlled by fatty acid/cholesterol composition?The mosaic refers to the variety of components and the asymmetrical aspect of the leafletsFluidity is due to the fact that the components are not covalently linked so they can move laterally (most common) or transversely (which requires energy so is more rare)Cholesterol keeps membranes more stable at a wider range of temperatures, by preventing fatty acids from packing in tightly at low temperatures, but its rigidity maintains structure at high temperatures Increased unsaturation and shorter fatty acid chains increase fluidityDescribe membrane fusion and the processes that rely on itFusion is the process that binds 2 originally distinct and separate lipid bilayers by merging together their hydrophobic cores.It is useful for endocytosis, phagocytosis, transporting nutrients and waste via vesicles, fertilization (joining of the egg and sperm)Lecture 5 Describe the ‘big picture’ of membrane transportSmall hydrophobic molecules can easily diffuse across the hydrophobic portion of the membrane, however larger or charged molecules need help from protein transports. Transporters can be very specific to the substrates they let through, allowing some molecules across the membrane but blocking others; hence the semi-permeable nature of membranesDescribe, compare and contrast the types of diffusionSimple diffusion is the movement of molecules without the aid of energy or transport proteinsFacilitated diffusion requires aid of a transporter protein (i.e. ion channels). Passive transport does not require energy input; active transport does.Enzyme catalysis aids in unfavourable movement of molecules, i.e. moving them against their concentration gradient. Requires either primary or secondary energy input from ATP Classification of transports: Passive, Active (primary or secondary), Channels, Carriers, Uniporters, Cotransporters (symport or antiport)Be able to describe the GLUT family of transporters as
View Full Document
Unlocking...