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Biology exam notes

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BIOL 1090
Andrew Bendall

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BiologyNovember30111004 PMThe CellBASIC PROPERTIES OF CELLShighly complex and organized maintain and utilize a genetic program reproduction generation or daughter cells acquire and utilize energy support enzymecatalyzed chemical reactions engage in mechanical activities respond to stimuli sustain selfregulation evolve1prokaryoticbacteria structurally simpler 2 eukaryoticprotists fungi plants animals structurally more complexCell is highly complexand organizedcontain largeof parts organized with respect to time and space parts interact with little tolerance for error fidelity of interactions is maintained through control and regulation of partsprovides great precision in cellular activities conserved throughout evolutionViruses are noncellular macromolecular packages that can function and reproduce only with living cellsoutsideof cells a virus exists as an inanimate particle virion virion comprised of small amount of DNA or RNA encoding a few to hundreds of genes protein capsule capsidViruses bind to a cell surface via specific proteins and enter celldefines cell types virus can infect and host range virus utilizes cellular machinery to synthesize nucleic acids and proteins assemble new virus particlesBiological membranesfluid mosaic modellipid bilayer proteins integral transmembrane peripheral lipidanchored components are mobile and can interactCommon properties6nm thick stable flexible capable of self assembly different membranes contain different types of lipids and proteinsdifferent functionsIntegralspan lipid bilayer lipid anchoredattached to lipid in the bilayer peripheralassociate with surfaces of lipid bilayerAsymmetricaltwo leaflets have distinct lipid composition many pms outer leaflet contains glycolipids and glycoproteins lipids and proteins with carbohydrate attachedMembrane fluidity determined by nature of lipids unsaturated lipids increase fluidity saturated lipids reduce fluidity tempwarming increases fluidity liquid crystal cooling decreases fluiditycrystalline gel crucial to cell functionbalance between ordered rigid structure and disordered structure allows mechanical support and flexibility dynamic interactions between membrane components proteins can come together reversibly membrane assembly and modification must be maintained lipid and composition of membranes can be changed by desaturation of lipids exchange of lipids chains not necessary in birds or mammalsLipid raftsmembrane microdomains lipids rafts are small areas of plasma membrane that are enriched in certain types of lipids cholesterolrelatively rigid some membrane proteins accumulate in rafts may form functional compartment Biological membranes are dynamiclipids move easily laterally within leaflet lipid movement to other leaflet is slow membrane proteins can diffuse with bilayermovement proteins restricted some proteins do not move rapid movement spatially limited long range diffusion is slow biochemical modification can dramatically alter proteins mobility in the membrane part of signal transduction Membrane fluidity crucialmust be maintained in response to changes in temp not necessary in birds or mammals lipid composition of membranes can bechanged by desaturation of lipids exchange of lipid chainsMovement across the membranelipid bilayers dont allow many compounds to pass through freely small uncharged molecules cross relatively easily OCO NO HO 222largepolarcharged compounds cant easily cross specific mechanisms exist for controlled transport 4 mechanismspassive nonmediated and transporter mediated active transporter mediated 4 ways simple diffusionvery small uncharged molecules downgradient OCOHO osmosis 2222diffusion through channelsmall charged molecules ions down concentration gradient NaKCaCl ion channels formed by integral membrane proteins that line aqueous porechannels selective allowing only 1 type of ion to pass move down concentration gradient channels gated open and close3 typesvoltagegated channels Kchannel responds to change in charge across membrane ligandgated channels CFTRchannel responds to binding of specific molecule the ligand mechanogated channelchannel responds to physical force on membrane stretchfacilitated diffusioncompound binds specifically to IMP called facilitative transporter change in conformation of transporter allows compound to be released on other side of membrane compound moves downgradient eg glucose transporter active transportcompound binds specifically to IMP called active transporter change in conformation of transporter allows compound to be released on other side of membrane compound moves upgradient requiresenergy NaKATPase maintains cellular Na and KExtracellular space most cells have glycocalyxassembly of carbohydrate groups attached to proteins and lipids on the outside of PMmediates cellcell and cellECM interactions provides mechanical protection serves as a barrier to some particles binds regulatory factors special cellcell contact specialized cellsubstratum contactExtracellular matrix many cells of multicellular organisms contact an extracellular matrix ECM organized network of material produced and secreted by cells important functions sites for cell attachment physical support for cells substrate through which cells can move contains regulatoryfactors signals separatedefine tissues components are produced by cells and assemble into a networkproteins and glycoproteins collagen fibronectin laminin proteoglycansproteins with polysaccharide chains ECM very dynamic environment cells bind to ECM via integrins and this influences cell survival and cellular activities cellECM interactions define tissue and organ function eg basement membraneCell wallbacteria and plants surrounded by cell wall plant cell walls composed of cellulose hemicellulose pectin and proteins provide structural support to cell and to organism as a whole skeleton protect cell from mechanical damage and pathogens contain biochemical informationMain functions of intracellular compartmentsMitochondria 2 membranes1 outer mitochondrial membranecontains many enzymes with diverse metabolic functions porinslarge channels when open membrane is freely permeable eg to ATP 2 inner mitochondrial membranehigh protein lipid ratio 31 forms doublelayered foldssheetscristae cristaeincrease membrane surface area contain machinery for aerobic respiration and ATP formation rich in a phospholipid called cardiolipin characteristic of bacterial membranes Aqueous compartments 1 intermembrane space 2 matrixhigh proteingellike consistency mitochondrial ribosomes mitochondrial DNAencodes polypeptides that are integrated into the IMM ribosomes tRNAOxidation Phosphorylation ATP synthesis1 electron transport and proton pumping high energy electrons pass from coenzymes NADH FADH in matrix to electron carriers 2in IMM series of ecarriers respiratory enzyme complexes I II III IV electron transport chain energy transfer at each complex used to pumpH from matrix into intermembrane space eventually low energy eis transferred to terminal eacceptor O HO produced 2 proton movement down elctrochemical gradient powers ATP 22synthesis controlled movement of protons back across IMMvia ATP synthase potential energy in electrochemical gradient across IMM is converted into ATP in the matrixMitochondria and apoptosisa normal occurrence in which a coordinated sequence of events leads to death of a cell characterized by shrinkage of cell blebbing of plasma membrane fragmentation of DNA and nucleus loss of attachment to other cells engulfment by phagocytosis intrinsic pathwayinitialized by intracellular stimuli proapoptotic proteins stimulate mitochondria to leak proteins eg cytochrome c release of apoptotic mitochondrial proteins commits cell to apoptosisSecretory cellpolar structure synthesized in rough ER processed in ER further processed in ER concentrated in vesicles delivered to plasma membraneGreen fluorescent proteinfrom jellyfish can be genetically fused with cellular protein fusion protein can be expressed in cells fluorescence form fusion protein is visualized microscope monitoring fusion protein provides info about endogenous proteinVesicular transport traffickingtransport of material between compartments organelle PM vise versa organelle organelle utilizes transport vesiclesbud off donor compartment fuse with acceptor compartment targeted movement directeduses cytoskeleton and motor proteins sorting signals recognized by receptors orientation of protein with respect to cytoplasm and interior membrane bound compartments is maintained during travel through endomembrane system 1 movement of vesicleusesbiology 1090 exam review Page 1
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