Bich 410 1st Edition Exam # 3 Study GuideI. LipidsA. Functioni. Lipids in the form of a bilayer are essential components of biological membranes.ii. Lipids containing hydrocarbon side chains serve as energy stores.iii. Many intra- and intercellular signaling events involve lipid molecules.iv. Lipid structure variable—multiple functions possibleB. Fatty Acidsi. Fatty acids are carboxylic acids with long-chain hydrocarbon side groups and hydrophilic head groupsii. Fatty acids can form micelles and take part in bilayer structure formation, but usually occur in esterified forms and serve as major components of other various lipidsiii. Saturated- no double bonds, unsaturated- cis double bondsiv. The degree of saturation is important as it impacts the ability of fatty acids to aggregate1. The presence of double bonds introduces kinks in the tails, preventing the efficient packing of fatty acids.v. Double bonds decreases the melting pointvi. Make sure you have the table of common fatty acids memorized- common name, number of carbons, how many double bonds (if any) and where they occurC. Triacylglycerolsi. fatty acid triesters of glycerolii. non-polar, water insoluble, and the major energy reservoirs in animalsiii. storage, insulation and energyiv. they associate and localize to a specific type of cell known as adipocytes or fat cellsD. Glycerophospholipidsi. addition of the phospho-alcohol head group in place of an esterified fatty acid side chain introduces a polar functional groupii. The presence of this polar group shifts the molecule from being highly hydrophobic to be being amphipathic – making it highly suitable for function within a membrane where the hydrophobic portion is buried in the interior of the membrane and the hydrophilic headgroup becomes solvent exposediii. Know how to name these, know the different head groupsE. SphingolipidsThese 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.i. The basic building block is a ceramide, a sphingosine with a fatty acid joined withan amide linkage.ii. Different head groupsiii. Play a role in the CNSF. Sphingomyelinsi. glycerophospholipid due to the head group being phosphocholineii. They possess the sphingosine backbone and the amide-linked fatty acid which forms the ceramideiii. Form the myelin sheath in neuronsG. Cerebrosidesi. Glycolipidii. Headgroup is a single sugariii. Found in animal muscle and nerve cellsH. Steroidsi. Cholesterolii. Four fused nonplanar ringsII. MembranesA. Why form membranes?i. Water prefers polar interactionsii. Water prefers to self-associate, through H-bondsiii. The hydrophobic effect promotes self-association of lipids in water to maximize entropyB. Compositioni. Membranes that carry out fewer such functions (such as myelin sheaths) are richer in lipidii. Membranes that carry out many enzyme-catalyzed reactions and transport activities are richer in proteinC. Structurei. Lipids form ordered structures spontaneously in waterii. Very few lipids exists as monomersiii. Micelles bury the nonpolar tails in the center of a spherical structureiv. The amphipathic molecules that form micelles are each characterized by a critical micelle concentration (CMC)D. Fluid Mosaic Modeli. The phospholipid bilayer is a fluid matrixii. The bilayer is a two-dimensional solventiii. Lipids and proteins can undergo rotational and lateral movementiv. Peripheral and integral proteinsE. Peripheral Proteinsi. not strongly bound to the membraneii. They may form ionic interactions and H bonds with polar lipid headgroups or with other proteinsiii. Or they may interact with the nonpolar membrane core by inserting a hydrophobic loop or an amphiphilic α-helixiv. can be dissociated with mild detergent treatment or with high salt concentrationsF. Integral Proteinsi. strongly embedded in the bilayerii. They can only be removed from the membrane by denaturing the membrane (organic solvents, or strong detergents)iii. Often are transmembraneiv. Surprising diversity in integral proteinsv. in all cases, the portions of the protein in contact with the nonpolar core of the lipid bilayer are dominated by α-helices and β-sheetsG. Amino Acidsi. The sequence of a transmembrane protein is adapted to the transition from water to the hydrophobic core and then to water againii. Hydrophobic amino acids are found most often in the hydrocarbon interioriii. Charged and polar residues occur commonly at the lipid-water interfaceiv. Trp, His, and Tyr are mixtures of polar and nonpolar parts. They are found often at the lipid-water interfacev. Arg, Asp, Asn, Gln, Glu, Lys, Pro more unfavorable in centervi. Ala, Gly, Ile, Leu, Met, Phe, Val more favorable in centervii. His, Tyr, Trp favorable at membrane-water interfacesH. Porinsi. pore-forming proteinsii. Most arrange in membrane as trimersiii. High homology between various porinsI. Why Beta sheets for membrane proteins?i. Genetic economy- need less informationii. Alpha helix requires 21-25 residues per transmembrane strandiii. Beta-strand requires only 9-11 residues per transmembrane strandiv. With beta strands, a certain amount of genetic material can make more trans membrane segmentsJ. Lipid Anchored proteinsi. Amide-Linked Myristoyl Anchors1. The lipid anchor is always myristic acid2. It is always N-terminal3. It is always linked to a Gly residueii. Thioester-linked and Acyl Anchors1. A broader specificity for lipids - myristate, palmitate, stearate, oleate all found2. Broader specificity for amino acid links - Cys, Ser, Thr are all foundiii. Thioether-linked Prenyl Anchors1. Prenylation refers to linking of "isoprene"-based groups2. Isoprene groups include farnesyl and geranylgeranyl groupsiv. Glycosyl Phosphatidylinositol Anchors1. GPI anchors are more elaborate than others2. Always attached to a C-terminal residue3. Ethanolamine link to an oligosaccharide linked in turn to inositol of PI4. She likes these!! Know them and study the figure with them!K. Proteins that redistribute membrane lipidsi. ATP-dependent flippases move PS (and some PE) from the outer leaflet to the inner leafletii. ATP-dependent floppases move amphiphilic lipids (including cholesterol, PC, andsphingomyelin) from the inner leaflet to the outer leaflet of the membraneiii. Bidirectional scramblases (Ca2+-activated but ATP-independent) randomize lipids across the membrane and thus degrade membrane lipid asymmetryL. Solid