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11 Cards in this Set
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Operational definition of lipids Seven classes of lipids plus distinguishing features |
Small, water insoluble molecule 1. Fatty acids: carboxylic acids with long hydrocarbon chain 2. Triacylglycerol: glycerol molecule with fatty acid chains esterified to hydroxyl group 3. Glycerophospholipid: glycerol molecule with C1 attached to saturated FA, C2 attached to unsaturated FA, C3 attached to a phospholipid 4. Sphingolipid: sphingosine backbone with fatty acid attached to N2, C1 attached to a head group 5. Sterols: lipids containing core of four fused rings (3 with 6C, 1 with 5c), hydrophilic head group 6. Waxes: esters of a long FA and a long alcohol 7. Eicosanoids: 20C, arachidonyl acyl chain derivative, act as paracrine hormones |
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Key fatty acids (6) How do fatty acid melting points vary |
1. Palmitic acid (16:0) 2. Stearic acid (18:0) 3. Oleic acid (18:1; d9) 4. Linoleic acid (18:2; d9, 12) 5. Linolenic acid (18:3; d9,12,15) 6. Arachidonic acid (20:4; d5, 8, 11, 14) Increasing chain length increases melting point due to van der Waals forces More cis double bonds decrease MP due to disruption of packing of acyl chains |
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Why are TAGs such a good source of energy (2) Key glycerophopholipids (5,2) |
1. Highly reduced - can donate many electrons 2. Extremely hydrophobic and thus can be stored without water - takes up less space 1. Phosphatidate - H 2. Phosphatidylethanolamine - ethanolamine (C-C-NH3) 3. Phosphatidylcholine - choline (C-C-N(CH3)3) 4. Phosphatidylserine - serine (R group is methyl - attaches to P) 5. Phosphatidylglycerol - glycerol (one o is estered onto the P) 1. Phosphatidylinositol - ring structure 2. Cardiolipin - big chain |
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Key sphingolipids to recognize |
1. Ceramide - H 2. Sphingomyelin - phosphocholine 3. Cerebroside - single sugars 4. Ganglioside - complex oligosaccharide with negatively charged head group |
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Major lipid components of eukaryotic membranes - difference in prokaryotes Basic properties of membranes (5) What are the terms for membrane fluidity and what consequences do they have How do prokaryotes and eukaryotes regulate membrane fluidity What effect does cholesterol have on membrane fluidity |
Glycerophospholipids, sphingolipids, cholesterol Bacterial dont have cholesterol 1. Amphipathic 2. Form bilayers and are naturally self-sealing 3. Impermeable to large molecules and small polar/charged molecules 4. Often have proteins embedded within membrane 5. Lipids and proteins can diffuse laterally but very rarely transversely Liquid-ordered state (too cold) - reduced fluidity, poor permeability - enzyme function is halted Liquid-disordered state (too hot) - increased fluidity, too much permeability - homeostasis disrupted Pro: change length of fatty acid chains or their saturation Eu: increase or decrease cholesterol concentration Acts as a fluidity buffer - slows the transition between Lo and Ld |
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Classes of membrane proteins (4) How to remove Strength of binding |
1. Integral: fully or partially imbedded 2. Lipid anchored: covalently bonded to a lipid 3. Peripheral: bound to one side of the membrane via H-bond, electrostatic, or hydrophobic interactions 4. Amphitropic: bind reversibly to membrane Integral: detergents or organic solvents Peripheral: pH or salt changes Lipid-anchored: intermediate Amphitropic: removes on its own in equilibrium Integral > Lipid > Peripheral > Amphitropic |
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How do integral membrane proteins span a membrane (2) with examples (3 each) Function of bacteriorhodopsin and AQP How does AQP work |
1. One or more alpha helices a. ATP synthase b. Aquaporin (AQP) c. Bacteriorhodopsin 2. Several membrane-spanning b-strands; forms antiparallel b-sheet then b-barrel a. FepA - iron ions in b. OmpLA - two beta-barrels, lipid substrate enzyme c. Maltoporin - 3 barrels - transfers maltose Bacteriorhodopsin - light-driven proton pump AQP - hydrophilic transmembrane channel for water Phospholipid tails bind tightly with hydrophobic aa side chains forming a hydrophilic core Arg residues in the channel repel any positively charged ions keeping H+ out |
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What lipids are in lipid-anchored proteins What makes membranes asymmetric What drives molecule movement in facilitated diffusion Why are transporters necessary Examples of facilitated diffusion transporters How can they be changed from open to closed state |
1. Palmitate - either cysteine (thioester) or serine 2. Myristate to N-terminus of glycine 3. Farnesyl group (isoprenoid) or geranylgeranyl group to C terminal cysteine 4. Glycosylated derivative of phosphatidylinositol (GPI-anchored proteins) Glycosylated proteins with the carbohydrates on the extracellular side of the membrane Solute gradient Free energy barrier very high (needs to break hydration shell) - transporter specificity reduces this barrier and speeds up rate of diffusion K+, Na+ channels, glucose transporters (GLUTs) Ligand binding or voltage changes |
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Primary difference of active transport from facilitated diffusion Primary active transport vs. secondary Examples of each Symporters vs. antiporters |
Requires energy from another source other than the solute's own gradient Primary: uses energy from ATP hydrolysis to push a solute against its gradient Eg. Na+/K+ ATPase - 2K+ in, 3 Na+ out with hydrolysis of ATP Secondary: uses another molecule moving down its concentration gradient to move the solute against its gradient Symporter: two solutes moving in the same direction across a membrane Eg. Lactose permease: moves H+ and lactose into the cell Antiporter: two solutes moving in opposite directions across a membrane Eg. Na+/H+ exchange proteins: Na+ in while H+ is pumped out |
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What is the main function of CoA What enzyme synthesizes malonyl CoA, what does it require Mechanism of action What special group is on the ACP group of fatty acid synthetase |
Carrier of acyl groups Acetyl CoA carboxylase (ACC) - biotin (Vit B7) and ATP 1. Enz-biotin + ATP + HCO3- --> Enz-biotin-CO2 + ADP + Pi + H+ 2. Enz-biotin-CO2 + Acetyl CoA --> Malonyl CoA + Enz-biotin Phosphopanthetheine (from vit B5) like CoASH |
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What are the steps of round one of fatty acid synthesis (6) How does the fatty acid chain get lenghtened? |
1. Malonyl/Acetyl CoA transferase (MAT) attaches an acetyl group to b-ketoacetyl synthetase (KS) 2. MAT transfers a malonyl CoA to Acyl Carrier Protein (ACP) 3. Condensation - KS synthesizes b-ketoacyl ACP by transferring an acetyl group to malonyl CoA with the loss of CO2 4. Reduction - ACP arms swings into active site of b-ketoacyl reductase (KR) and substrate is reduced to b-hydroxyacyl ACP through electron donation by NADPH 5. Dehydration - b-hydroxyacyl ACP dehydrotase (DH) removes an OH from the b-carbon and an H from the a-carbon to form trans d2 enoyl ACP 6. Reduction - enoyl ACP reductase removes the C2-C3 double bond with NADPH as the electron donor creating acyl ACP MAT moves the acyl group to KS and then transfers another malonyl group to ACP. Malonyl group then attacks the carbonyl of the acyl chain to begin the cycle again |
