Sinh học - Chapter 4: A tour of the cell

Chapter 4A Tour of the Cell0IntroductionCells are the simplest collection of matter that can live.Cells were first observed by Robert Hooke in 1665.Working with more refined lenses, Antoni van Leeuwenhoek later describedblood,sperm, andorganisms living in pond water.© 2012 Pearson Education, Inc.IntroductionSince the days of Hooke and Leeuwenhoek, improved microscopes have vastly expanded our view of the cell.© 2012 Pearson Education, Inc.Figure 4.0_1Introduction to the CellThe Nucleus andRibosomesThe EndomembraneSystemEnergy-ConvertingOrganellesThe Cytoskeletonand Cell SurfacesChapter 4: Big IdeasFigure 4.0_2INTRODUCTION TO THE CELL© 2012 Pearson Education, Inc.4.1 Microscopes reveal the world of the cellA variety of microscopes have been developed for a clearer view of cells and cellular structure.The most frequently used microscope is the light microscope (LM)—like the one used in biology laboratories.Light passes through a specimen, then through glass lenses, and finally light is projected into the viewer’s eye.Specimens can be magnified up to 1,000 times the actual size of the specimen.© 2012 Pearson Education, Inc.4.1 Microscopes reveal the world of the cellMagnification is the increase in the apparent size of an object.Resolution is a measure of the clarity of an image. In other words, it is the ability of an instrument to show two close objects as separate.© 2012 Pearson Education, Inc.4.1 Microscopes reveal the world of the cellMicroscopes have limitations.The human eye and the microscope have limits of resolution—the ability to distinguish between small structures.Therefore, the light microscope cannot provide the details of a small cell’s structure.© 2012 Pearson Education, Inc.4.1 Microscopes reveal the world of the cellUsing light microscopes, scientists studiedmicroorganisms,animal and plant cells, andsome structures within cells.In the 1800s, these studies led to cell theory, which states thatall living things are composed of cells andall cells come from other cells.© 2012 Pearson Education, Inc.Figure 4.1AFigure 4.1B10 m1 m100 mm(10 cm)10 mm(1 cm)1 mmHuman heightLength ofsome nerveand musclecellsChickeneggFrog eggHuman eggParamecium100 m10 m1 m100 nm10 nmMost plant andanimal cells1 nm0.1 nmNucleusMost bacteriaMitochondrionSmallest bacteriaVirusesRibosomeProteinsLipidsSmall moleculesAtomsUnaided eyeLight microscopeElectron microscopeFigure 4.1CFigure 4.1DFigure 4.1E4.2 The small size of cells relates to the need to exchange materials across the plasma membraneCell size mustbe large enough to house DNA, proteins, and structures needed to survive and reproduce, butremain small enough to allow for a surface-to-volume ratio that will allow adequate exchange with the environment.© 2012 Pearson Education, Inc.Figure 4.2A3311Total volumeTotal surfaceareaSurface-to-volume ratio254 units227 units327 units3162 units26The plasma membrane forms a flexible boundary between the living cell and its surroundings.Phospholipids form a two-layer sheet called a phospholipid bilayer in whichhydrophilic heads face outward, exposed to water, andhydrophobic tails point inward, shielded from water.4.2 The small size of cells relates to the need to exchange materials across the plasma membrane© 2012 Pearson Education, Inc.Membrane proteins are eitherattached to the membrane surface orembedded in the phospholipid bilayer.Some proteins form channels or tunnels that shield ions and other hydrophilic molecules as they pass through the hydrophobic center of the membrane.Other proteins serve as pumps, using energy to actively transport molecules into or out of the cell.4.2 The small size of cells relates to the need to exchange materials across the plasma membrane© 2012 Pearson Education, Inc.Figure 4.2BOutside cellHydrophilicheadsHydrophobictailsPhospholipidInside cellChannelproteinProteinsHydrophilicregion ofa proteinHydrophobicregion ofa protein4.3 Prokaryotic cells are structurally simpler than eukaryotic cellsBacteria and archaea are prokaryotic cells.All other forms of life are composed of eukaryotic cells.Prokaryotic and eukaryotic cells havea plasma membrane andone or more chromosomes and ribosomes.Eukaryotic cells have amembrane-bound nucleus and number of other organelles.Prokaryotes have a nucleoid and no true organelles.© 2012 Pearson Education, Inc.4.3 Prokaryotic cells are structurally simpler than eukaryotic cellsThe DNA of prokaryotic cells is coiled into a region called the nucleoid, but no membrane surrounds the DNA.The surface of prokaryotic cells maybe surrounded by a chemically complex cell wall,have a capsule surrounding the cell wall,have short projections that help attach to other cells or the substrate, orhave longer projections called flagella that may propel the cell through its liquid environment.© 2012 Pearson Education, Inc.Figure 4.3FimbriaeRibosomesNucleoidPlasma membraneCell wallCapsuleFlagellaA TEM of the bacteriumBacillus coagulansBacterialchromosomeA typical rod-shapedbacterium4.4 Eukaryotic cells are partitioned into functional compartmentsThe structures and organelles of eukaryotic cells perform four basic functions.The nucleus and ribosomes are involved in the genetic control of the cell.The endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes are involved in the manufacture, distribution, and breakdown of molecules.© 2012 Pearson Education, Inc.4.4 Eukaryotic cells are partitioned into functional compartmentsMitochondria in all cells and chloroplasts in plant cells are involved in energy processing.Structural support, movement, and communication between cells are functions of the cytoskeleton, plasma membrane, and cell wall.© 2012 Pearson Education, Inc.4.4 Eukaryotic cells are partitioned into functional compartmentsThe internal membranes of eukaryotic cells partition it into compartments.Cellular metabolism, the many chemical activities of cells, occurs within organelles.© 2012 Pearson Education, Inc.4.4 Eukaryotic cells are partitioned into functional compartmentsAlmost all of the organelles and other structures of animals cells are present in plant cells.A few exceptions exist.Lysosomes and centrioles are not found in plant cells.Plant but not animal cells havea rigid cell wall,chloroplasts, anda central vacuole.© 2012 Pearson Education, Inc.Figure 4.4ASmoothendoplasmicreticulumRoughendoplasmicreticulumNUCLEUS:NuclearenvelopeChromatinNucleolusRibosomesGolgiapparatusMitochondrionPlasma membranePeroxisomeCYTOSKELETON:MicrotubuleIntermediatefilamentMicrofilamentLysosomeCentrioleNOT IN MOSTPLANT CELLS:Figure 4.4BNUCLEUS:Nuclear envelopeChromatinNucleolusGolgiapparatusRoughendoplasmicreticulumRibosomesPeroxisomeCentral vacuoleNOT IN ANIMAL CELLS:ChloroplastCell wallPlasmodesmaMitochondrionPlasma membraneCell wall ofadjacent cellSmoothendoplasmicreticulumCYTOSKELETON:MicrotubuleIntermediatefilamentMicrofilamentTHE NUCLEUS AND RIBOSOMES© 2012 Pearson Education, Inc.4.5 The nucleus is the cell’s genetic control centerThe nucleuscontains most of the cell’s DNA andcontrols the cell’s activities by directing protein synthesis by making messenger RNA (mRNA).DNA is associated with many proteins in structures called chromosomes.© 2012 Pearson Education, Inc.4.5 The nucleus is the cell’s genetic control centerThe nuclear envelopeis a double membrane andhas pores that allow material to flow in and out of the nucleus.The nuclear envelope is attached to a network of cellular membranes called the endoplasmic reticulum.© 2012 Pearson Education, Inc.4.5 The nucleus is the cell’s genetic control centerThe nucleolus isa prominent structure in the nucleus andthe site of ribosomal RNA (rRNA) synthesis.© 2012 Pearson Education, Inc.Figure 4.5Two membranesof nuclear envelopeNucleusChromatinNucleolusPoreEndoplasmicreticulumRibosomes4.6 Ribosomes make proteins for use in the cell and exportRibosomes are involved in the cell’s protein synthesis.Ribosomes are synthesized from rRNA produced in the nucleolus.Cells that must synthesize large amounts of protein have a large number of ribosomes.© 2012 Pearson Education, Inc.4.6 Ribosomes make proteins for use in the cell and exportSome ribosomes are free ribosomes; others are bound.Free ribosomes aresuspended in the cytoplasm andtypically involved in making proteins that function within the cytoplasm.Bound ribosomes areattached to the endoplasmic reticulum (ER) associated with the nuclear envelope andassociated with proteins packed in certain organelles or exported from the cell.© 2012 Pearson Education, Inc.Figure 4.6RibosomesERCytoplasmEndoplasmicreticulum (ER)Free ribosomesBoundribosomesDiagram ofa ribosomeProteinmRNAColorized TEM showingER and ribosomesTHE ENDOMEMBRANE SYSTEM© 2012 Pearson Education, Inc.4.7 Overview: Many cell organelles are connected through the endomembrane systemMany of the membranes within a eukaryotic cell are part of the endomembrane system. Some of these membranes are physically connected and some are related by the transfer of membrane segments by tiny vesicles (sacs made of membrane).Many of these organelles work together in thesynthesis,storage, and export of molecules. © 2012 Pearson Education, Inc.4.7 Overview: Many cell organelles are connected through the endomembrane systemThe endomembrane system includesthe nuclear envelope,endoplasmic reticulum (ER),Golgi apparatus,lysosomes,vacuoles, andthe plasma membrane.© 2012 Pearson Education, Inc.4.8 The endoplasmic reticulum is a biosynthetic factoryThere are two kinds of endoplasmic reticulum—smooth and rough.Smooth ER lacks attached ribosomes.Rough ER lines the outer surface of membranes.Although physically interconnected, smooth and rough ER differ in structure and function.© 2012 Pearson Education, Inc.Figure 4.8ASmooth ERRough ERRibosomesNuclearenvelopeFigure 4.8BTransport vesiclebuds offmRNARibosomePolypeptideGlycoproteinRough ERSugarchainSecretoryproteininside trans-port vesicle43214.8 The endoplasmic reticulum is a biosynthetic factorySmooth ER is involved in a variety of diverse metabolic processes.Smooth ER produces enzymes important in the synthesis of lipids, oils, phospholipids, and steroids.Other enzymes help process drugs, alcohol, and other potentially harmful substances.Some smooth ER helps store calcium ions.© 2012 Pearson Education, Inc.4.8 The endoplasmic reticulum is a biosynthetic factoryRough ER makesadditional membrane for itself andproteins destined for secretions.© 2012 Pearson Education, Inc.4.9 The Golgi apparatus finishes, sorts, and ships cell productsThe Golgi apparatus serves as a molecular warehouse and finishing factory for products manufactured by the ER.Products travel in transport vesicles from the ER to the Golgi apparatus.One side of the Golgi apparatus functions as a receiving dock for the product and the other as a shipping dock.Products are modified as they go from one side of the Golgi apparatus to the other and travel in vesicles to other sites.© 2012 Pearson Education, Inc.Figure 4.9Golgi apparatusGolgi apparatusTransportvesicle fromthe Golgi“Shipping” side of GolgiapparatusTransportvesiclefrom ER“Receiving” sideof Golgiapparatus123444.10 Lysosomes are digestive compartments within a cellA lysosome is a membranous sac containing digestive enzymes.The enzymes and membrane are produced by the ER and transferred to the Golgi apparatus for processing.The membrane serves to safely isolate these potent enzymes from the rest of the cell.© 2012 Pearson Education, Inc.4.10 Lysosomes are digestive compartments within a cellLysosomes help digest food particles engulfed by a cell.A food vacuole binds with a lysosome.The enzymes in the lysosome digest the food.The nutrients are then released into the cell.© 2012 Pearson Education, Inc.Figure 4.10A_s1DigestiveenzymesLysosomePlasma membraneFigure 4.10A_s2DigestiveenzymesLysosomeFood vacuolePlasma membraneFigure 4.10A_s3DigestiveenzymesLysosomeFood vacuolePlasma membraneFigure 4.10A_s4DigestiveenzymesLysosomeFood vacuolePlasma membraneDigestion4.10 Lysosomes are digestive compartments within a cellLysosomes also help remove or recycle damaged parts of a cell.The damaged organelle is first enclosed in a membrane vesicle.Then a lysosomefuses with the vesicle,dismantles its contents, andbreaks down the damaged organelle.© 2012 Pearson Education, Inc.Figure 4.10B_s1LysosomeVesicle containingdamaged mitochondrionFigure 4.10B_s2LysosomeVesicle containingdamaged mitochondrionFigure 4.10B_s3LysosomeVesicle containingdamaged mitochondrionDigestion4.11 Vacuoles function in the general maintenance of the cellVacuoles are large vesicles that have a variety of functions.Some protists have contractile vacuoles that help to eliminate water from the protist.In plants, vacuoles mayhave digestive functions,contain pigments, orcontain poisons that protect the plant.© 2012 Pearson Education, Inc.Figure 4.11AContractilevacuolesNucleusFigure 4.11BCentral vacuoleChloroplastNucleus4.12 A review of the structures involved in manufacturing and breakdownThe following figure summarizes the relationships among the major organelles of the endomembrane system.© 2012 Pearson Education, Inc.Figure 4.12SmoothERNucleusTransportvesicle from ERto GolgiGolgiapparatusLysosomeVacuolePlasmamembraneNuclearmembraneRough ERTransportvesicle fromGolgi to plasmamembraneENERGY-CONVERTING ORGANELLES© 2012 Pearson Education, Inc.4.13 Mitochondria harvest chemical energy from foodMitochondria are organelles that carry out cellular respiration in nearly all eukaryotic cells.Cellular respiration converts the chemical energy in foods to chemical energy in ATP (adenosine triphosphate).© 2012 Pearson Education, Inc.4.13 Mitochondria harvest chemical energy from foodMitochondria have two internal compartments.The intermembrane space is the narrow region between the inner and outer membranes.The mitochondrial matrix containsthe mitochondrial DNA,ribosomes, andmany enzymes that catalyze some of the reactions of cellular respiration.© 2012 Pearson Education, Inc.Figure 4.13MatrixCristaeInnermembraneOutermembraneMitochondrionIntermembranespace4.14 Chloroplasts convert solar energy to chemical energyChloroplasts are the photosynthesizing organelles of all photosynthesizing eukaryotes.Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar molecules.© 2012 Pearson Education, Inc.4.14 Chloroplasts convert solar energy to chemical energyChloroplasts are partitioned into compartments.Between the outer and inner membrane is a thin intermembrane space.Inside the inner membrane isa thick fluid called stroma that contains the chloroplast DNA, ribosomes, and many enzymes anda network of interconnected sacs called thylakoids.In some regions, thylakoids are stacked like poker chips. Each stack is called a granum,where green chlorophyll molecules trap solar energy.© 2012 Pearson Education, Inc.Figure 4.14Inner andoutermembranesGranumStromaChloroplastThylakoid4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosisMitochondria and chloroplasts haveDNA andribosomes.The structure of this DNA and these ribosomes is very similar to that found in prokaryotic cells.© 2012 Pearson Education, Inc.4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosisThe endosymbiont theory proposes thatmitochondria and chloroplasts were formerly small prokaryotes andthey began living within larger cells.© 2012 Pearson Education, Inc.Figure 4.15MitochondrionNucleusEndoplasmicreticulumEngulfing ofphotosyntheticprokaryoteChloroplastHost cellMitochondrionHost cellEngulfingof oxygen-using prokaryoteSomecellsTHE CYTOSKELETON AND CELL SURFACES© 2012 Pearson Education, Inc.4.16 The cell’s internal skeleton helps organize its structure and activitiesCells contain a network of protein fibers, called the cytoskeleton, which functions in structural support and motility.Scientists believe that motility and cellular regulation result when the cytoskeleton interacts with proteins called motor proteins.© 2012 Pearson Education, Inc.4.16 The cell’s internal skeleton helps organize its structure and activitiesThe cytoskeleton is composed of three kinds of fibers.Microfilaments (actin filaments) support the cell’s shape and are involved in motility.Intermediate filaments reinforce cell shape and anchor organelles.Microtubules (made of tubulin) give the cell rigidity and act as tracks for organelle movement.© 2012 Pearson Education, Inc.Figure 4.16Actin subunitNucleusNucleusMicrofilamentIntermediate filamentFibrous subunits7 nm10 nmTubulin subunitsMicrotubule25 nm4.17 Cilia and flagella move when microtubules bendWhile some protists have flagella and cilia that are important in locomotion, some cells of multicellular organisms have them for different reasons.Cells that sweep mucus out of our lungs have cilia.Animal sperm are flagellated.© 2012 Pearson Education, Inc.Figure 4.17ACiliaFigure 4.17BFlagellumFigure 4.17COuter microtubule doubletCentralmicrotubulesRadial spokeDynein proteinsPlasma membraneFigure 4.17C_1Outer microtubule doubletCentralmicrotubulesRadial spoke Dynein proteins4.17 Cilia and flagella move when microtubules bendA flagellum, longer than cilia, propels a cell by an undulating, whiplike motion.Cilia work more like the oars of a crew boat.Although differences exist, flagella and cilia have a common structure and mechanism of movement.© 2012 Pearson Education, Inc.4.17 Cilia and flagella move when microtubules bendBoth flagella and cilia are made of microtubules wrapped in an extension of the plasma membrane.A ring of nine microtubule doublets surrounds a central pair of microtubules. This arrangement is called the 9 + 2 pattern andanchored in a basal body with nine microtubule triplets arranged in a ring.© 2012 Pearson Education, Inc.4.17 Cilia and flagella move when microtubules bendCilia and flagella move by bending motor proteins called dynein feet.These feet attach to and exert a sliding force on an adjacent doublet.The arms then release and reattach a little further along and repeat this time after time.This “walking” causes the microtubules to bend.© 2012 Pearson Education, Inc.4.18 CONNECTION: Problems with sperm motility may be environmental or geneticIn developed countries over the last 50 years, there has been a decline in sperm quality.The causes of this decline may beenvironmental chemicals orgenetic disorders that interfere with the movement of sperm and cilia. Primary ciliary dyskinesia (PCD) is a rare disease characterized by recurrent infections of the respiratory tract and immotile sperm.© 2012 Pearson Education, Inc.4.19 The extracellular matrix of animal cells functions in support and regulationAnimal cells synthesize and secrete an elaborate extracellular matrix (ECM) thathelps hold cells together in tissues andprotects and supports the plasma membrane.© 2012 Pearson Education, Inc.4.19 The extracellular matrix of animal cells functions in support and regulationThe ECM may attach to a cell through glycoproteins that then bind to membrane proteins called integrins. Integrins span the plasma membrane and connect to microfilaments of the cytoskeleton.© 2012 Pearson Education, Inc.Figure 4.19EXTRACELLULAR FLUIDCYTOPLASMMicrofilamentsof cytoskeltonPlasmamembraneIntegrinConnectingglycoproteinGlycoproteincomplexwith longpolysaccharideCollagen fiber4.20 Three types of cell junctions are found in animal tissuesAdjacent cells communicate, interact, and adhere through specialized junctions between them.Tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells.Anchoring junctions fasten cells together into sheets.Gap junctions are channels that allow molecules to flow between cells.© 2012 Pearson Education, Inc.Figure 4.20Tight junctionsprevent fluid frommoving between cellsTight junctionAnchoringjunctionGap junctionPlasma membranesof adjacent cellsExtracellular matrix4.21 Cell walls enclose and support plant cellsA plant cell, but not an animal cell, has a rigid cell wall thatprotects and provides skeletal support that helps keep the plant upright against gravity andis primarily composed of cellulose.Plant cells have cell junctions called plasmodesmata that serve in communication between cells.© 2012 Pearson Education, Inc.Figure 4.21VacuolePlant cellwallsPlasmodesmataCytoplasmPrimary cell wallSecondary cell wallPlasma membrane