Cell Bio Module II
Cell Bio Module II BIOL 541
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This 14 page Study Guide was uploaded by . Notetaker on Tuesday August 11, 2015. The Study Guide belongs to BIOL 541 at Kansas State University taught by Dr. Stella Lee in Fall 2014. Since its upload, it has received 88 views. For similar materials see Cell Biology in Biology at Kansas State University.
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Date Created: 08/11/15
Module 2 Chapter 4 A Surface areavolume a Volume stays the same but surface area increases with many cells b Cells specialize to maximize surface areavolume ratio i Microvilli increases surface area B Diffusion unassisted movement of substance from region of high concentration to low concentration a Size of cell is limited by diffusion rates b Larger size of molecule lower the diffusion rate is signi cant for macromolecules c Eukaryotic cells i Carrier proteins can transport ii Cytoplasmic streaming cyclosis in plants to move cytoplasmic contents iii Vesicles transported along microtubules to move molecules d For reactions to occur appropriate reactants must collide e Cell volume increases number of molecules needs to increase proportionally C Organism grouping a Prokaryotes no nucleus bacteria archaea b Eukarytoes nucleus animals plants fungi algae protozoa c Based on rRNA sequencing archaea are more closely realted to Eukarya i Archaea considered to have descended from common ancestor that also gave rise to eukaryotes d Differences i Bac amp archa small euk big ii Bac amp archa binary ssion euk mitosis amp meiosis iii Bac transcription amp translation bacterial type arch euk iv Bac amp archea circular DNA euk linear DNA v Bac amp arch nucleoid no nucleus euk nucleus vi Bac amp arch no organelles euk organelles vii Exocytosis amp endocytosis cytoskeleton ALL EUK D Euka rytoes a Plasmas membrane i Proteins 1 Enzymes catalyze reactions with membranes 2 Others serve as anchors for structural components of cytoskeleton 3 Transport move substances across membrane 4 Receptors external signals b Nucleus contains DNA and surrounded by nuclear envelope i Nuclear pores each of which is transport channel lined with nuclear pore complex ii Xsomes visualzed during mitosis and during interphase dispered as chromatin iii Nucleoli sites of ribosomal RNA synthesis c Organelles i Mitochondrion site of aerobic respiration comparable in size to bacteria 1 Contains inner amp outer mitochondrial membranes 2 Small circular moleucles of DNA encoding some RNAs and proteins for mitochondrial function 3 Function a Oxidation of sugar in energy from food and sotres ATP b Molecules for mitochondrial function are localized on cristae folding of inner membranes or matrix uid that lls inside of mitochondrion c Tissues with high demand for ATP have many mitochondrion muscles sperm ii Chloroplast site of photosynthesis 1 6 7 8 Photouses solar energy amp c02 to produce sugars and other organic compounds reverse of mitochondrial reactions that oxideze glucose INTO C02 Contains inner and outer membranes system of attened membranous sacs called thylakoids stacked into grana Stroma inner membrane space Reactions involved in reduction of C02 to sugar occur in stroma Chloroplast contain their own ribosomes small circular DNA lnduce nitrogen form N03 in solids to ammonia NH3 form needed for protein synthesis SO4 reduce to H25 needed for protein synthesis iii Endosymbiont theory evolved from ancient bacteria 1 They were engulfed by other cells iv Endoplasmic reticulum tubular membranes and attened sacs called cisternae 1 2 3 Internal space lumen Er continuous with other membranes in cell connect with nuclear envelope vesicles to Golgi Smooth a Synthesis of lipids and steroids b Responsible for inactivating and detoxi ying potentially harmful substances c Sarcoplasmic reticulum critical functions in contraction Golgi closely related to ER consists of stack of attned vesicles known as cisternae a Important role in processing andpackaging secretory proteins and in complex polysaccharide b Accepts vesicles that bud off ER c Secretor and membrane proteins are mainly glycosylated addition of shortchained carbohydrates process that begins in eR and completed in Golgi d Each stack 46 cisternae 40100 stacks 5 Secretory vesicles once processed by golgi materials to be exported from cell are packaged into secretory vesicles a Move to plasma membrane and fuse with it releasing contents outside the cells b ER golgi sec vesicles lysosomes make up the endomembrane system of cell 6 Lysosome organelles contain hydrolases enzymes that can digest many types of bio moleucles a Special carb coating on inner lysosome membrane protects it from digestion b Functions i Degredation of foreign material ii Breaking down macromolecules such as membrane proteins and lipids digesting organelles that are damaged or no longer needed 7 Peroxisomes resemble lysosomes in size and appearance a Produce hydrogen peroxide b Catalase decomposes hydrogen peroixide c Detoxi cation of harmful compounds ethanol formaldehyde d Breakdown of longchain fatty acids e In plants i During germination of fatstoring seeds specialized peroxisomes called glyoxysomes play a role in converting stored fat into carbs ii Leaf peroxisomes photosynthetic tissues because of their role in photorespiration lightdependent uptake of oxygen and release of C02 8 Vacuoles membranebounded vacuole a Animal an dyeast used storage or transport b Plant central vacuole to maintain turgor pressure that keeps the plant from wilting 9 Ribosomes not organelles a Found is all cells but differ slightly in bacteria archaea and euk in size and composition b Sedimentation coef cient measure of how rapidly particle sediments in and ultracentrifuge expressed in Svedberg units S based on size amp shape c 805 euk 7OS bacteria and archaea 10Microtubules cylinders of longitudinal arras of proto laments with hollow center called lumen a Proto lament linear polymer of tubulin with polarity i Tubulin dimeric protein consisting of a amp B tuban 11Micro laments smallest components of cytoskeleton a Connections with plasma membrane to affect movement b Produce cleavage furrow in cell division c Contribute to cell shape d Structure polymers of protein actin synthesized as monomer called Gactin 12ntermediate laments Size in between microtubules and micro laments Most stable and least soluble components Tension bearing role Structure six classes contain proto laments tetramers that interact with one another for form intermediate laments apem v Cytoplasm 1 Cytosol semi uid substance where organelles are 2 Synthesis takes place in here 3 Cytosol is permeated by the cytoskeleton a 3D array of micro laments microtubules and intermediate lamnets b Cell movement and division c Proto laments a amp B tubulin heterodimers amp ends d Actin monomers two interwinded chains of F actin and ends e Intermediate laments eight proto laments joined end to end with staggered overlaps no polarity f Microtubules vi Extracellular matrix amp cell wall 1 ECM animal cells consists mainly of collagen bers and proteoglycans 2 Cell wall plants amp fungal cells consist mainly of cellulose micro brils 3 Bacterial cells consist of peptidoglycans long chains of N acetylglucosamine and Nacetylmuramic acid a Plant cell wall mainly of cellulose brils embedded in gellike polysaccharide matrix more exible b Secondary cell wall rigid forms by deposition of additional cellulose amp lignin on inner surface of primary cell wall c Plasmodesmata cytoplasmic bridge connecting to neighboring cells pass through cell wall passage of water small solutes 4 Animal cells a Gap junctions exchange of aterial between cells b Rightjunctions sealing spaces between cells c Adhesion junctions cellcell adhesion vii Viruses 1 Virus consists of DNA or RNA core surrounded by protein coat 2 Viroid small circular RNA molecules 250400 bp long 3 Prions proteinaceous infective particles 4 Noncellular parasitic particles incapable of a freelinving existence 5 No cytoplasm viii Prions infective particles responsible for neurological disesases like scrapie kuru and mad cow 1 Abnormally folded versions of normal cellular proteins aggregates prone 2 Cannot be destroyed by cooking or boiling a Found in deer amp elk hunters test meat for prions Chapter 7 A Membranes a Permeability very small particles may diffuse water CO b Signal transduction bind signal molecules to their receptors triggers chemical events on inner membrane c Fluid mosaic model membrane as two uid lyaers of lipids with proteins within and on layers i Lipid soluble substances into cella dn concluded cell surface had some ort of coat ii Langmuir studied phospholipids and found the were amphiathatic iii Gorter amp grndel extracted lipids from RBc and spread lipids in monolayer on water surface 1 Film on water was twice the surface area of BC suggesting lipids on cell surface consisted of two layers iv Robertson presence of membrane around cells and organelles 1 Rilaminar structure leading to suggestion of common membrane structure called the unit membrane v Shortcomings of davsondanielli model 1 Proteinlipid ratio is not the same for all cells 2 Membranes susceptible to digestion by phospholipases suggesting that membranes lipids are exposed 3 Unable to isolate surface proteins from membranes unless organic solvents or detergents were usedproteins partially embedded in membrane vi Proteins 1 Integralembedded in lipd bilayer due to hydrophobic regions 2 Peripheral hydrophilic and located on surface of bilayer Lipidanchored proteins hydrophilic and attached to bilayer by covalent attachments to lipid molecules embedded in bilayer vii Lipids 1 Phospholipids most abundant a Glycerolbased phosphoglycerides amp sphingosine based b Glycolipids formed by addition of carbohydrates i Clycerolbased and some are sphingosin based ii Cerebrosides and gangliosides most common sphingosin 1 Cere neutral glycolipdids each molecules has uncharged sugar as its head 2 Gangli has oligosaccharide head group with one or more neg charged sialic acid residues 3 Both prominent in brain and nerve cells iii Glycerol MGDG DGDG 2 Thinlayer chromatography lipids can be isolated separated studied using nonpolar solvents such as acetone and chloroform a Separated by polarities 3 Lipds can move freely a Rotationphospholipids about their axes b Move via lateral diffusion rapid amp random c Ransverse diffusion ip op sides i Phospholipids translocators of ippases to ip op membranes especially is smooth ER d Asymmetry i Membrane asymmetry is difereence tbetween two monolayers types of lipids degree of saturation of fatty acids B Cell to cell communication a Embryonic development celltocell contacts are often mediated by cadherin molecules C Fluid bilayer a Permits movemtn of both lipids and proteins b Can move several um per second in monolayer c Measurement i Lipid molecules labeled with uorescence dye 1 Bleach dye in small area b laser beam creating dark spot on membrane 2 Measuring reappearance of uorescence rate of diffusion d Fluidity changes with temp decreasing as temp falls and vice versa e Transition temp T the temp when it becomes uid i Change of state called phase transition Membrane to function needs to be above Tm i Temp can be measured by differential scanning calorimetry f 1 D Fatty acids Fluidity depends on lipid it contains length fatt acid chains and degree of saturation both affect uidity chains have higher Tm shortchain and fatty acids have lower Tm Saturated fatty acids pack well in membrane a an g saturated Sterols Uptake of heat is measured as temp is increased Tm is point of max heat absorption as membrane changes rom gel to uid Unsaturated fatty acids do not pack well do to double bonds lower Tm Unsaturated fatty acids have cis double bonds unlike trans amp i Cholesterol is a uidity buffer sterold in other organism may function similarly 1 2 3 4 Decreases uidity and increases Tm Prevents hydrocarbon chains of phospholipids from packing together tightly and reduces tendency of membranes to gel when cooling Above Tm uidity Below Tm uidity ii Decrease permeability of membranes to ions and small polar molecules 1 2 Regulation Fill space between hydrocarbon chains of phospholipids Blocks routes that ions and small molecules would pass thru membrane i Varying lipid composition of membranes ii Most important in organisms that cannot regulate their body temp 1 Poikilotherms use homeoviscious adaptation compensating for changes in temp by altering length of saturation of fatty acids h Lipid rafts localized regions of membrane lipids in association with speci c protiens called lipid microdomains i Dynamic chaning composition as lipids and proteins move into and out ii High on cholesterol glycosphingolipid phospholipids with acyl chain raftassociated proteins iii Functions 1 2 Detecting and responding to exracelluar signals Transport nutrients and ions across membrane 3 Binding of activated immune system cells to their microbial targets 4 Transport cholera toxin into intestinal cells i Caveolae small askshaped invaginations of plasma membrane structurally related to lipid rafts i Contain cholesterol binding protein called caveolin enriched in sphingolipids and lipid anchored proteins j Fluidity uid part lipids mosaic part lipid domains rafts caveolae membrane proteins k Freezefracture microscopy technique that can separate two monolayers of membrane lipid l Transmembrane proteins i Anchored to lipid bilayer by one or more hydrophobic transmembrane segments ii Polypeptide chain appears to span membrane in alpha helical conformation 2030 amino acids long iii Some arranged as closed B sheet called B barrel m Singlepass membrane proteins Cterminus extending from one surface of membrane and nterminus from other i Ex glycophorin singlepass protein on erthyrocyte ii Multipass membrane proteins 220 transmembrane segments n Peripheral membrane proteins i Lack discrete hydrophobic regions do not penetrate lipid bilayer ii Bound to membrane surfaces through weak electrostatic forces and hydrogen bonds iii Some hydrophobic residues typ play role in anchoring them to membrane surface iv Easily separated from membranes by chaning pH or ionic strength 0 Lipid anchored membrane proteins i Polypeptide chains on surfaces of membranes covalently bonded to lipid molecules ii Fatt acid or isoprenyl anchored 1 Inner side of plasma membrane as well as on intracellular membrane 2 Synthesized in cytosol iii GPI anchored 1 Outer side of plasma membrane 2 Snthesize in ER lumen p SDS gels i Electrophoresis groups techniuqes use electric eld to separate charged molecules ii Separation depends on charge amp size iii Media polyacrylamide or agarose iv Sds page separate proteins samples solubuilized in SDS to give net negative charge before loading onto gel v Isolating peripheral membrane proteins 1 Alter pH or ionic strength using chelating agents to remove calcium using urea to break hydrogen bonds vi Isolating integral membrane proteins 1 Using detergents to disrupt hydrophobic interactions and dissolve lipid bilayer vii Visualization 1 Coomassie brilliant blue protein gel can be stained with dye such as to show proteins 2 Western blotting proteins on gel be transferred onto nitrocellulose membrane and labeled with antibodies against speci c proteins to reveal identiy 3D structures 1 Xray chrystallogrpahy determine structure of proteins that can be isolated in crystalline form a Hard to isolate amp cyrstallize b Michel deisenhofer Huber solved rst membrane protein structure using x ray 2 Alternative hydropathic analysis can be used to predict tranmembrane segments of protein ix Hydropathy analysis computer program identi es clusters of hydrophobic residues calculating a index for successive windows along protein Viii E Membrane proteins a b c d Exhibit asymmetric orientation with respect to lipid bilayer Once in place proteins cannot move across membrane from one surface to other Moleucles of particular protein oriented same way in membrane Glycosylated addition of carb side chain i Occurs in ER amp Golgi ii Nlinked glycosylation attached to amino group on side chain is asparagine iii Olinked attached to hydroxyl group on side chain of serine or threonine Most common sugars with carb chains attached galactose mannose Nacetylglucosamine sialic acid Glycoproteins i Cellcell recognition ii Carb groups protrude on outer surface of membrane iii Lectins plant proteins that bind speci c sugar groups very tightly can be used to study membrane glycoproteins 1 Wheat germ agglutinin binds terminal N acetylglucosamine 2 Concanavalin binds inernal mannose Vary in mobility I Some move freely whereas other are constrained because they are anchored to protein complexes ii Tested by frye amp edidin39s cell fusion experiements iii Photobleaching recovery experimetns can be used to determine diffusion rates h Glycocalyx carb groups of glycoproteins amp glycolipids form surface coat Chapter 8 A Cells amp transport processes a Simple diffusion unaided movement dictated by differences in concentration of solute on two sides of membrane i Most solutes cannot cross this way ii Water glycerol oxygen C02 oils steroids iii Disffusion movment is always towards equilibrium iv Factors affecting diffusion 1 Size polarity charge a Size molecular weight less than 100 can diffuse b Water diffuses faster even though its polar c Partition coef cient meaures of polarity of solute i Ratio of solubility in organic solvent to its solubility in water ii More nonpolar higher coef cient more readily moving across a membrane iii Tryptophan leucine valine nonpolar higher coef cients iv Charge molecules of water form shell of hydration around polar substances in order for substances to move into membrane water must be removed amp requires energy v Rate 1 Proportional to concentration gradient SD is exergonic process 2 Vinward PdeltaS a S solute concentration outside inside b P permeability coef cient c Simple diffusion linear relationship between inward ux of solute and concentration gradient of solute vi Osmosis diffusion of water across membrane 1 Water molecules uncharged not affected by membrane potential 2 Not appreciablydelta different on opposite sides of membrane 3 Decrease deltaG water moves from regions of low to high solute moving toward region of lowest free energy higher solute b Facilitate diffusion transprote protein assisted of solutes DOWN gradient no energy required passive transport i Water glycerol glucose sodium potassium Ca ii Carrier bind solute molecules on one side of membrane release the solute on other side 1 Two states binding or nonbinding alternating conformation model Involves binding a substrate form intermediate after change product is released Can be regulated by external factors High speci city for single compound Has MM kinetics Also has competitive inhibitions Uniport carrier protein transprots single solute Coupled transport two solutes transported simultaneously a Symport two solutes move in same direction b Antiport two solutes move in opposite directions 9 Glucose transporter is a uniport carrier for glucose a Anion exchange protein is an antiport anion carrier b Glut1 forms cavity with hydrophilic side chains integral membrane protein i Reversible glucose concentration is kept low inside most animal cells hexokinase converts glucose to glucose phosphate glucose cannot bind carrier protein any longer iii Channel form hydrophilic channels thru membranes to provide passage route for solutes 1 Must faster than carrier 2 Three types a Ion channgle allow rapid passage of speci c ions i Cant allow NA K CA and Cl ii Selectivity is based on amino aicd side chain iii Channels are gated open in close to stimulus 1 Voltage 2 Ligand binding of certain substances 3 Mechanosensitive mechanical forces acting on membrane b Porins allow rapid passage of various solutes i Less specific transmembrane segments cross membrane as B barrels 1 B barrel has water lled pore at center poar side chains face inside of pore nonpoar side chains face outside of barrel c Aquaporins rapid passage of water i Discovered by agre and mackinnon ii Especifally in RBC kidneys root cells in plants iii Structure 6 a helical transmembrane proteins form four central channels H20 enters one at a time Iquot 3 Pquot39gtW c Active transport proteinmediated movement of solutles up the gradient requires energy i Glucose sodium potassium Ca ii Couples endergonic transport to an exergonic process usually ATP hydrolysis iii Many proteins are pumps because energy is required to move substances against their concentration gradients iv Unidirectional different from diffusion in direction of transport v lntrinsic directionality go against gradient vi Direct couples with exergonic ATP hydrolysis as energy source 1 Accumulation of solute molecueles on one side of memebrane is couple directl to exergonic chemical reaction 2 Transport ATPases or ATPase pumps a 4 types P V F ABC b P phosphorylationP2 sodiumpotassium pump c V for vacuolea i Pump protons into organelles ii Two protein domains d F for factor called ATPases i Found in bacteria mitochondira chloroplasts ii Can function in reverse iii Two protein domains e ABC ATP binding cassette i Bacteria were importers ii Structure have four proteins domains iii Medical relevance MDR transport protein multidrug resistance vii lndirect couples with another exergonic solute transport 1 Favorable movement of one solutes down its gradient drives the unfavorable movement of the other up its gradient Can be symport or antiport Symport resulting high extracellular concentration of Na is a driving force for uptake of sugars and amino acids 4 Proton gradients drive indirect active transport proton rather than Na 5 Examples of active transport NaK pump Naglucose amp bacteriorhodospin a NAK pump KinsideKoutside is about 351 electrochemical potentials for sodium and potassium are essential as driving force for coupled transport and for ttransmission of nerve impulses i Structure2 K in for every 3 Na out tatrameric protein ii Allosteric protein open to inside for high af nity for NA open to outside high af nity for K UJN b NAglucose 2 sodium per 1 glucose molecule goes in together c Bacteriorhodopsin small integral membrane protein uses energy from photons of light to drive active transport of protons out of the cell i Lightabsorbing pigment chromophore ii Absorbs a photo one double bond of all trans retinal becomes higher energy Concentration gradient i Movent of molecules has no net charge is determined by its concentration gradient ii Simple or facilitated dissuion involve exergonic movemtn down deltaG iii Active movement up deltaG Electrochemical potential movment of ion combined effect of its concentration gradient and charge gradient across membrane i Membrane potential Vm Active transport ions i Cells have excess negatively charged solutes ii Charge difference favors inward movement of cations NA outward movment of anions such as Cl iii Asymmetric distribution active transport of ions across membrane results in asymmetric distribution of ions inside and out of cell 1 Outside NA and CL Oxygen amp erythrocytes i Oxygen gas traverses the bilayer readily by simple diffusion ii Erythrocytes take up oxygen in lungs where oxygen concentration is high release it in body tissues where oxygen concentration is low B Energetics of transport a b Uncharged solutes only variable is concentration gradient across membrane Charged solutes both concentration and electrical potenetial are relevant i Delta G for transport deltaGnot RTln 5 inside 5 outside Keq i Uncharged always be 1 ii deltaGnot is always 0 things going in the cell i RT ln insideoutside ii S inside lt 5 outside deltaG is negative iii S insidegt 5 outside deltaG is positive Charged solutes i Membrane potential Vm always negative and favors the inward movemtn of cations and opposes their outward movement ii If charged solute regular equation zFVm 1 2 charge on ion 2 F 23062 3 Vm membrane potential deltaG RT n1 1F6511
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