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Fun 1 Exam 2 A
Lipids and Membranes
| Question | Answer |
|---|---|
| 18C amino alcohol | sphingosine |
| amide linkages of fatty acids to the nitrogen of sphingosine | ceramides |
| represent a phosphorus containing subclass of sphingolipids | sphingomyelins |
| ceramides with one or more sugars beta-glycosidic linkages at the 1-hydroxyl group | glycosphingolipids |
| glycosphingolipids with ONE sugar | cerebrosides |
| glycosphinglipids with 2 or more sugars | globosides |
| ceramides with 3 or more sugars, one of which is sialic acid | gangliosides |
| gangliosides = ceramides with _#_ or more sugars, one of which is ______ | 3; sialic acid |
| esters of long chain alcohols with long chain fatty acids | waxes |
| highly insoluble lipid found coating animal skin and fur, in leaves of many plants and bird feathers | waxes |
| lipid with ether linkage instead of acyl group at C-1 position of glycerol | ether glycerophospholipids |
| ether glycerophospholipids with unsaturated alkyl chain (C-2) | plasmalogens |
| terpenes are based on ____ structure | isoprene (5C) |
| all sterols (incl. cholesterol) are ____-based molecules | terpene |
| many _____ are recognized by their characteristic flavors or odors (ex. limonene, citronellal, pinene, menthol) | monoterpenes |
| C20 terpenes; include retinal, phytol, and gibberellins | diterpenes |
| lanosterol (constituent of wood fat) is example of ____ (terpene) | triterpene |
| tetraterpene; carotenoid found in ripe fruit esp. tomatoes | lycopene |
| 1. initiation point for synthesis of carbohydrate polymers in animals = ____ 2. analogous alcohol of (1) in bacterial systems that consists of 11 ISOPRENE units | 1. dolichol phosphate 2. undecaprenol (AKA bactoprenol) |
| delivers sugars from cytoplasm for the synthesis o cell wall components such as peptidoglycans, lipopolysaccharides, and glycoproteins | undecaprenyl phosphate (isoprene) |
| ____ compounds serve as side chains of Vit. K, the ubiquinones, plastoquinones, and tocopherols (Vit. E) | polyprenyl compounds (isoprene) |
| functions as both a hormone and visual pigment of the vertebrate eye | vitamin A |
| vitamin A derivative which regulates gene expression in the development of epithelial tissues; isoprene (hormone fxn of Vit A) | retinoic acid |
| vitamin A derivative, pigment that initiates the response of rod and cone cells of the retina to light; isoprene (visual pigment fxn of vit A) | retinal |
| What activates inactive retinal (Vitamin A1 derivative) to change to functional retinal (pigment for vision)? | VISIBLE LIGHT makes 11C-12C double bond TRANS from cis |
| _____ is not itself biologically active, but is converted by enzymes in the liver and kidney to 1,25-dihydroxycholechalciferol, a hormone that regulates CALCIUM UPTAKE in the intestine and CALCIUM LEVELS in kidney and bone | Vitamin D3 |
| deficiency of vitamin D leads to _____ | defective bone formation |
| collective name for a group of closely related lipids called TOCOPHEROLS | Vitamin E |
| hydrophobic, associate with the membranes and lipoproteins in blood, collectively called Vitamin E --Biological antioxidants | Vitamin E |
| Why are tocopherols (Vit E) considered biological antioxidants? | the aromatic ring reacts with and destroys the most reactive forms of oxygen radicals and other free radicals, protecting unsaturated FA from oxidation and preventing oxidative damage to membrane lipids |
| principle symptom of vitamin E deficiency? | fragile erythrocytes |
| The aromatic ring of _____ undergoes a cycle of oxidation and reduction during the formation of active PROTHROMBIN, a blood plasma proteolytic protein essential in blood clot formation | Vitamin K |
| activated ____ splits peptide bonds in the blood protein fibrinogen to convert it to fibrin, the insoluble fibrous protein that holds blood clots together | prothrombin (formed from Vit K) |
| Vit K deficiency leads to ______ | slows blood clotting (can be fatal) |
| Coumadin (widely prescribed anticoagulant) and Warfarin (component of rodent poisons) act as _____ | antagonists of Vitamin K in body (so slows/prevents blood clotting) |
| stimulates the carboxylation of proteins participating in blood clotting cascade = ___1___ Carboxylation of these coagulation factors is catalyzed by a carboxylase that requires the ___2___ form of (1), molecular oxygen, and CO2 | 1. Vitamin K 2. reduced |
| Enzyme targeted by Coumadin and Warfarin? | Vitamin K epoxide reductase (blood clotting requires redox reactions of Vitamin K) |
| Steroids: based on a core structure consisting of __ 6-membered rings and __ 5-membered rings, all fused together | 3 6-membered 1 5-membered |
| most common steroid in animals and precursor for all other steroids in mammals | cholesterol |
| serve many functions in animals incl. salt balance, metabolic function, and sexual function | steroid hormones |
| BILE ACIDS = polar derivatives of ____ BILE SALTS = synthesized from ____ and stored in the ____ | cholesterol synthesized from CHOLESTEROL in LIVER stored in GALL BLADDER |
| Bile = ? | mixture of bile acids, cholesterol, and pigments from breakdown of RBC |
| Bile is secreted into the ____ after a fatty meal Function of bile? | small intestine acts as a DETERGENT emulsifying dietary fats to make them more readily accessible to DIGESTIVE LIPASES |
| taurocholic acid = example of ____ | bile acid |
| impt precursor for many steroid hormones (incl. testosterone, estradiol, cortisol, aldosterone, prednisolone, prednisone) | cholesterol |
| formation of an amide linkage between a FA and a sphingosine produces a _____ | ceramide |
| constitute the boundaries of cells and intracellular organelles; also provide a surface where many impt biological reactions such as electron transport, oxidative phosphorylation, electrical activity, and signaling occur | membranes |
| T/F Lipids form ordered structures spontaneously in water. | true |
| Monomer lipids? | Very few lipids exist as monomers |
| How do micelles react to nonpolar solvents? | reverse, tails go to outside |
| two ways lipid bilayers can form? | 1. unilamellar vesicles (liposomes) 2. multilamellar vesicles |
| Components of the Fluid Mosaic Model? | 1. phospholipid bilayer = fluid matrix 2. bilayer = two-dimensional solvent 3. Lipids and proteins can undergo rotational and lateral mov't 4. 2 classes of proteins: peripheral (extrinsic) and integral (intrinsic) |
| Where does cholesterol occur in membrane? | integrated |
| how has lipid diffusion (migration of lipids and proteins in the bilayer) been shown? | NMR and EPR as well as fluorescence measurements |
| How are proteins and lipids arranged in membrane? | LATERAL ASYMMETRY of both lipids and proteins - they can cluster in the plane of the membrane and are not uniformly distributed |
| What might induce phase separations of components of membrane (form liposomes)? | divalent cations such as Ca2+ |
| membrane protein known to SELF-ASSOCIATE or form clusters in nonrandom formations) | Bacteriorhodopsin forms clusters known a PURPLE PATCHES in membranes of Halobacterium halobium |
| Transverse Asymmetry of proteins: Bark Bretscher showed that the ___ of glycophorin is extracellular wherease ____ is intracellular | N-terminus = extracellular C-terminus = intracellular |
| Transverse Asymmetry of lipids: in most cell membranes, the composition of the ____ is different from the _____ | Outer monolayer is different from the inner monolayer |
| proteins that move lipids from one monolayer to the other Where do these proteins get energy? | Flippase Proteins Some are passive and do not require an energy source Most require energy hydrolysis of ATP (ex. in erythrocytes) |
| What type of flippase can generate membrane asymmetries? | Active Flippase (uses ATP hydrolysis) |
| Phase transitions in membranes? **only pure lipid systems give sharp, well-defined transition temperatures | Below a certain transition temp - membrane lipids are rigid and tightly packed Above the transition temp - lipids are more flexible and mobile **The transition temperature is characteristic of the lipids in the membrane |
| What happens to membrane as it is WARMED? | Surface area increases as thickness decreases. Mobility of the lipid chains INC dramatically (goes through phase transition) |
| proteins which are NOT strongly bound to membrane, can be dissociated from the membrane by treatment with salt solutions or changes in pH | Peripheral proteins |
| proteins that are imbedded in bilayer; can removed only by agents capable of breaking up the hydrophobic interactions within the lipid bilayer itself --often transmembrane but not necessarily --Ex. glycophorin, bacteriorhodopsin | integral membrane proteins |
| A single transmembrane segment with globular domains on either end transmembrane segment is ____ (shape) and consists of __#__ hydrophobic amino acids | Glycophorin alpha helical; 19 AA |
| Extracellular portion of glycophorin (transmembrane protein) contains ____ which constitute ______ determinants | oligosaccharides; ABO and MN blood group determinants |
| spans the membrane of the human erythrocyte via a single alpha-helical transmembrane segment C-terminus faces _____ N-terminus points to _____ What attaches to the N-terminus? | Glycophorin A C-terminus faces cytosol of erythrocyte N-terminus faces extracellular side Carbohydrates |
| a 7-transmembrane-segment (7-TMS) protein --found in purple patches of Halobacterium halobium --consists of 7 transmembrane helical segments with short loops that interconnect the helices --light driven proton pump | Bacteriorhodopsin |
| Bacteriorhodopsin = a ____ protein, ___-driven proton pump found in _____ | 7-TMS protein LIGHT driven proton pump Purple patches of Halobacterium halobium |
| Where are porins found? | in both Gram - bacteria and in mitochondrial outer membrane |
| pore-forming proteins (30-50 kD) --general or specific (exclusion limits 600-6000) --most arrange in membrane as trimmers --high homology between various proteins --make beta barrels | Porins |
| Most porins arrange in membrane as ____ | trimers |
| PORIN from Rhodobacter capsulatus has _____ that transverses the membrane to form the pore | 16-stranded beta barrel |
| a relatively new class of membrane proteins; 4 types have been found: -amide-liked myristoyl anchors -thioester-linked fatty acyl anchors -thioether-linked prenyl anchors -glycosyl phosphatidylinositol anchors | Lipid-Anchored Membrane Proteins |
| Type of lipid-anchored membrane protein? --always myristic acid --always N-terminal --always a Gly residue that links | Amide-linked myristoyl anchors |
| The following proteins are examples of ____: cAMP-dependent protein kinase pp60^sro tyrosine kinase calcineurin B alpha subunits of G proteins gag protein of HIV-1 | amide-linked myristoyl anchors |
| amide-linked myristoyl anchors: 1. always ____ acid 2. always __-terminal 3. always a ___ residue that links | 1. myristic acid 2. N-terminal 3. Gly |
| N-myristoylation always occurs at _____ | N-terminal glycine residue |
| Anchor with broader specificity for lipids - myristat, Palmitate, stearate, oleate all found | Thioester-linked acyl anchors |
| The following are examples of _____: G-coupled protein receptors Surface glycoproteins of some viruses Transferrin receptor triggers and signals | Thioester-liked acyl anchors |
| S-pamitoylation always occurs at the ____ residues of polypeptide chain. | cysteine |
| G-protein coupled receptors, with seven transmembrane segments, may contain one (or two) palmitoyl anchors in thioester linkage to _____ residues in the __-terminal segment of the protein | cysteine; C-terminal |
| Anchors: Prenylation refers to linking of "isoprene" based groups --always Cys of CAAX (C=Cys, A=Aliphatic, X=any residue) --isoprene groups include farnesyl (15C, 3 double bond) and gernaylgeranyl (20C, 4 double bonds) gropus | Thioether-linked prenyl anchors |
| The following are examples of _____: yeast mating factors p21^ras nuclear lamins | Thioether-linked prenyl anchors |
| Proteins containing the C-Terminal sequence CAAX can undergo ____ reactions that place ____ at the CYSTEINE side chain | prenylation thioether linked farnesyl or geranylgeranyl groups |
| _____ is accompanied by the removal of the AAX peptide and the methylation of the carboxyl group of the cysteine residue, which has become the _____ residue | Prenylation; C-terminal |
| ____ is a small GTP-binding protein involved in cell signaling pathways that regulate cell growth and division --mutations in this are involved in 1/3 of all human cancers --it is dependent on prenylation and the proteolysis of the -AAX motif | RAS |
| Because the signaling activity of RAS is dependent on __1__, the reaction itself, as well as the proteolysis of the __2__ motif, and the methylation of the __3__, have been considered targets for development of NEW CHEMOTHERAPY strategies | 1) prenylation 2) -AAX motif (from the C-terminal sequence CAAX, the -AAX is removed) 3) prenylated Cys residue (what is left at the end of the C-terminal after proteolysis) |
| Anchors that are more elaborate than the others --always attached to C-terminal residue --Ethanolamine link to an oligosaccharide linked in turn to inositol of PI | Glycosyl Phosphatidyllinositol Anchors |
| GPI anchors are always attached to a ____ residue | C-terminal |
| The following are examples of _____: surface antigens adhesion molecules cell surface hydrolases | Glycosyl Phosphatidylinositol anchors |
| Core of Glycosyl phosphatidylinositol (GPI) = _______ Additional modifications may include FA at the ___ and ___ -OH groups | 3 mannose residues and a glucosamine (elaborate lipid-anchoring group) inositol and glycerol |
| When transported species simply move down its concentration gradient (from high cxn to low cxn) | passive diffusion |
| What does a high permeability coefficient signify? | passive diffusion is not the whole story |
| Passive diffusion of an UNCHARGED species depends on: | only the concentrations on the two sides of the membrane |
| Passive diffusion of a CHARGED species depends on: | 1. CONCENTRATION of particle Z 2. CHARGE of particle Z 3. ELECTRICAL DIFFERENCE across the membrane (delta psi) |
| How does facilitated diffusion occur? | solutes only move in the thermodynamically favored direction but proteins may facilitate transport increasing the rates of transport |
| 2 impt distinguishing features of facilitated diffusion? | 1. Solute only flows in favored direction 2. Transport displays saturation kinetics |
| How does energy input drive active transport processes? | Energy source and transport machinery are coupled so that solutes can flow against thermodynamic potential. Energy source may be ATP, light or a concentration gradient. |
| SODIUM PUMP: large protein (120kD and 35kD) 1) maintains intracellular ___ low and ___ high 2) Crucial for all organs but esp. ___ and ___ 3) ATP hydrolysis drives ___ out and ___ in | 1) Na low & K high 2) neural tissue and brain 3) Na+ out & K+ in |
| SODIUM PUMP: 1) Alpha subunit has 10 transmembrane ____ with a large cytoplasmic domain 2) ATP hydrolysis occurs via _____ 3) _____ inhibit by binding to outside | 1) helices 2) E-P intermediate 3) cardiac glycosides |
| For sodium pump what moves in and out per ATP? | 3 Na+ out and 2 K+ in |
| osteoclasts vs osteoblasts? | **Bone material undergoes ongoing remodeling. OsteoCLASTS tear down bone tissue OSTEOBLASTS build it back up |
| How do osteoclasts function? | by secreting acid into the space between the osteoclast membrane and the bone surface. Acid dissolves the Ca-phosphate matrix of the bone. **It is all driven by an ATP proton pump in the membrane |
| Proton pumps cluster on the ruffled border of ____ and function to pump protons into the space between the cell membrane and the bone surface. ____ ____ concentration in this space dissolves the mineral matrix of the bone | osteoclast cells High proton concentration |
| a member of a "superfamily" of genes/proteins that appear to have arisen as a "tandem repeat" --defeats efforts of chemotherapy --recognizes a broad variety of molecules and transports them out of the cell using the hydrolytic energy of ATP | MDR ATPase (AKA the P-glycoprotein) - an organic molecule pump |
| MDR ATPase: this multidrug transporter is postulated to have _#_ transmembrane alpha-helices and _#_ ATP binding sites **Some of cytotoxic drugs are transported by MDR ATPase (Colchicine, Vinblastine, Adriamycin, and Vincristine) | 12 transmembrane alpha-helices (HUGE!) 2 ATP binding sites |
| How is amino acid and sugar transport driven by ion gradients? | SECONDARY ACTIVE TRANSPORT Does not use ATP directly, but uses the gradient of other compounds ---> Symport and Antiport |
| Symport vs antiport (2* active transport) | Symport = ion and the AA or sugar are transported in the same direction across the membrane Antiport = ion and transported species move in opposite directions |
Created by:
erinlwilliams
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