Y khoa, y dược - Cells: The living units: part c

3 Cells: The Living Units: Part CLocated between plasma membrane and nucleusCytosolWater with solutes (protein, salts, sugars, etc.)Cytoplasmic organellesMetabolic machinery of cellInclusionsGranules of glycogen or pigments, lipid droplets, vacuoles, and crystalsCytoplasmMembranousMitochondriaPeroxisomesLysosomesEndoplasmic reticulumGolgi apparatusNonmembranousCytoskeleton Centrioles RibosomesCytoplasmic OrganellesDouble-membrane structure with shelflike cristaeProvide most of cell’s ATP via aerobic cellular respirationContain their own DNA and RNAMitochondriaFigure 3.17EnzymesMatrixCristaeMitochondrial DNARibosomeOuter mitochondrial membraneInner mitochondrial membrane(b)(a)(c)Granules containing protein and rRNASite of protein synthesisFree ribosomes synthesize soluble proteins Membrane-bound ribosomes (on rough ER) synthesize proteins to be incorporated into membranes or exported from the cellRibosomesInterconnected tubes and parallel membranes enclosing cisternaeContinuous with nuclear membraneTwo varieties:Rough ERSmooth EREndoplasmic Reticulum (ER)Figure 3.18aNuclearenvelopeRibosomesRough ERSmooth ER(a) Diagrammatic view of smooth and rough ERExternal surface studded with ribosomesManufactures all secreted proteinsSynthesizes membrane integral proteins and phospholipids Rough ERTubules arranged in a looping networkEnzyme (integral protein) functions:In the liver — lipid and cholesterol metabolism, breakdown of glycogen, and, along with kidneys, detoxification of drugs, pesticides, and carcinogens Synthesis of steroid-based hormones In intestinal cells—absorption, synthesis, and transport of fatsIn skeletal and cardiac muscle — storage and release of calciumSmooth ERStacked and flattened membranous sacsModifies, concentrates, and packages proteins and lipidsTransport vessels from ER fuse with convex cis face of Golgi apparatusProteins then pass through Golgi apparatus to trans faceSecretory vesicles leave trans face of Golgi stack and move to designated parts of cellGolgi ApparatusFigure 3.20 Protein-containing vesicles pinch off rough ERand migrate to fuse with membranes ofGolgi apparatus. Proteins aremodified withinthe Golgi compartments. Proteins arethen packagedwithin differentvesicle types, depending ontheir ultimatedestination.Plasmamem-braneSecretion byexocytosisVesicle becomeslysosomeGolgiapparatus Rough ERERmembranePhagosomeProteins incisternaPathway B:Vesicle membraneto be incorporatedinto plasmamembranePathway A:Vesicle contentsdestined for exocytosisExtracellular fluidSecretoryvesiclePathway C:Lysosome containing acid hydrolaseenzymes132Spherical membranous bags containing digestive enzymes (acid hydrolases)Digest ingested bacteria, viruses, and toxinsDegrade nonfunctional organellesBreak down and release glycogenBreak down bone to release Ca2+Destroy cells in injured or nonuseful tissue (autolysis)LysosomesOverall functionProduce, store, and export biological moleculesDegrade potentially harmful substancesEndomembrane SystemFigure 3.22GolgiapparatusTransportvesiclePlasmamembraneVesicleSmooth ERRough ERNuclear envelopeLysosomeNucleusEndomembrane SystemPLAYAnimation: Endomembrane SystemMembranous sacs containing powerful oxidases and catalasesDetoxify harmful or toxic substancesNeutralize dangerous free radicals (highly reactive chemicals with unpaired electrons) PeroxisomesElaborate series of rods throughout cytosolMicrotubules Microfilaments Intermediate filamentsCytoskeletonDynamic actin strands attached to cytoplasmic side of plasma membraneInvolved in cell motility, change in shape, endocytosis and exocytosisMicrofilamentsCilia and flagellaWhiplike, motile extensions on surfaces of certain cellsContain microtubules and motor moleculesCilia move substances across cell surfaces Longer flagella propel whole cells (tail of sperm)Cellular ExtensionsPLAYAnimation: Cilia and FlagellaFigure 3.27(a) Phases of ciliary motion.(b) Traveling wave created by the activity ofmany cilia acting together propels mucusacross cell surfaces.Power, orpropulsive,strokeLayer of mucusCell surfaceRecovery stroke, whencilium is returning to itsinitial position1234567MicrovilliFingerlike extensions of plasma membraneIncrease surface area for absorptionCore of actin filaments for stiffening Cellular ExtensionsFigure 3.28MicrovillusActinfilamentsTerminalwebGenetic library with blueprints for nearly all cellular proteinsResponds to signals and dictates kinds and amounts of proteins to be synthesizedMost cells are uninucleateRed blood cells are anucleateSkeletal muscle cells, bone destruction cells, and some liver cells are multinucleateNucleusFigure 3.29aChromatin (condensed)Nuclear envelopeNucleusNuclear poresNucleolusCisternae of rough ER(a)Double-membrane barrier containing poresOuter layer is continuous with rough ER and bears ribosomesInner lining (nuclear lamina) maintains shape of nucleusPore complex regulates transport of large molecules into and out of nucleusNuclear EnvelopeFigure 3.29bNucleusNuclearporesFractureline of outermembraneNuclear pore complexes.Each pore is ringed byprotein particles.Surface of nuclear envelope.Nuclear lamina. The netlikelamina composed of inter-mediate filaments formed bylamins lines the inner surfaceof the nuclear envelope.(b)Dark-staining spherical bodies within nucleusInvolved in rRNA synthesis and ribosome subunit assemblyNucleoliThreadlike strands of DNA (30%), histone proteins (60%), and RNA (10%)Arranged in fundamental units called nucleosomesCondense into barlike bodies called chromosomes when the cell starts to divideChromatinFigure 3.30Metaphasechromosome(at midpointof cell division)Nucleosome (10-nm diameter; eight histone proteins wrapped by two winds of the DNA double helix)Linker DNAHistones(a)(b)1 DNA doublehelix (2-nm diameter)2 Chromatin(“beads on a string”) structurewith nucleosomes 3 Tight helical fiber(30-nm diameter)5 Chromatid(700-nm diameter)4 Looped domain structure (300-nm diameter)