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Cell Structure and Function
Chapter 04
2Cell Structure Cell Structure and Functionand Function
OutlineOutline
Cell TheoryCell Theory
Cell SizeCell Size
Prokaryotic CellsProkaryotic Cells
Eukaryotic CellsEukaryotic CellsOrganellesOrganelles NucleusNucleus
Endomembrane SystemEndomembrane System
CytoskeletonCytoskeleton
Centrioles, Cilia, and FlagellaCentrioles, Cilia, and Flagella
3Cell Structure Cell Structure and Functionand Function
Cell TheoryCell Theory
A unifying concept in biologyA unifying concept in biology
Originated from the work of biologists Originated from the work of biologists SchleidenSchleiden and and SchwannSchwann in 1838-9 in 1838-9
States that:States that:All organisms are composed of cellsAll organisms are composed of cells German botanist Matthais Schleiden in 1838German botanist Matthais Schleiden in 1838
German zoologist Theodor Schwann in 1839German zoologist Theodor Schwann in 1839All cells come only from preexisting cellsAll cells come only from preexisting cells German physician Rudolph Virchow in 1850’sGerman physician Rudolph Virchow in 1850’s
Smallest unit of lifeSmallest unit of life
4Organisms and Cells
5Sizes of Living Things
6Cell Structure Cell Structure and Functionand Function
Cell SizeCell Size
Most much smaller than one millimeter (mm)Most much smaller than one millimeter (mm)
Some as small as one micrometer (Some as small as one micrometer (m)m)
Size restricted by Surface/Volume (S/V) ratioSize restricted by Surface/Volume (S/V) ratioSurface is membrane, across which cell Surface is membrane, across which cell acquires nutrients and expels wastesacquires nutrients and expels wastes
Volume is living cytoplasm, which demands Volume is living cytoplasm, which demands nutrients and produces wastesnutrients and produces wastes
As cell grows, volume increases faster than As cell grows, volume increases faster than surfacesurface
Cells specialized in absorption modified to Cells specialized in absorption modified to greatly increase surface area per unit volumegreatly increase surface area per unit volume
7Surface to Volume RatioSurface to Volume Ratio
TotalSurfaceArea(HeightWidthNumberOfSidesNumberOfCubes)
96cm2 192cm2 384cm2TotalVolume(HeightWidthLengthXNumberOfCubes)
64cm3 64cm3 64cm3SurfaceAreaPerCube/VolumePerCube(SurfaceArea/Volume)
1.5/1 3/1 6/1
TotalSurfaceArea(HeightWidthNumberOfSidesNumberOfCubes)
96cm2 192cm2 384cm2TotalVolume(HeightWidthLengthXNumberOfCubes)
64cm3 64cm3 64cm3SurfaceAreaPerCube/VolumePerCube(SurfaceArea/Volume)
1.5/1 3/1 6/1
8Cell Structure Cell Structure and Functionand Functionsciencescience
focusfocusMicroscopy Today:Microscopy Today:Compound Light MicroscopeCompound Light Microscope
Light passed through specimenLight passed through specimen
Focused by glass lensesFocused by glass lenses
Image formed on human retinaImage formed on human retina
Max magnification about 1000XMax magnification about 1000X
Resolves objects separated by 0.2 Resolves objects separated by 0.2 m, 500X m, 500X better than human eyebetter than human eye
9Cell Structure Cell Structure and Functionand Functionsciencescience
focusfocusMicroscopy Today:Microscopy Today:Transmission Electron MicroscopeTransmission Electron Microscope
Abbreviated T.E.M.Abbreviated T.E.M.
Electrons passed through specimenElectrons passed through specimen
Focused by magnetic lensesFocused by magnetic lenses
Image formed on fluorescent screenImage formed on fluorescent screen
Similar to TV screenSimilar to TV screen
Image is then photographedImage is then photographed
Max magnification 1000,000s XMax magnification 1000,000s X
Resolves objects separated by 0.00002 Resolves objects separated by 0.00002 m, m, 100,000X better than human eye100,000X better than human eye
10Cell Structure Cell Structure and Functionand Functionsciencescience
focusfocusMicroscopy Today:Microscopy Today:Scanning Electron MicroscopeScanning Electron Microscope
Abbreviated S.E.M.Abbreviated S.E.M.
Specimen sprayed with thin coat of metalSpecimen sprayed with thin coat of metal
Electron beam scanned across surface of Electron beam scanned across surface of specimenspecimen
Metal emits secondary electronsMetal emits secondary electrons
Emitted electrons focused by magnetic lensesEmitted electrons focused by magnetic lenses
Image formed on fluorescent screenImage formed on fluorescent screen
Similar to TV screenSimilar to TV screen
Image is then photographedImage is then photographed
11Cell Structure Cell Structure and Functionand Functionsciencescience
focusfocusMicroscopy Today:Microscopy Today:Immunofluorescence Light MicroscopeImmunofluorescence Light Microscope
Antibodies developed against a specific Antibodies developed against a specific proteinproteinFluorescent dye molecule attached to Fluorescent dye molecule attached to antibody moleculesantibody molecules
Specimen exposed to fluorescent antibodiesSpecimen exposed to fluorescent antibodiesUltra-violet light (black ligt) passed through Ultra-violet light (black ligt) passed through
specimenspecimenFluorescent dye glows in color where antigen Fluorescent dye glows in color where antigen is locatedis located
Emitted light is focused by glass lenses onto Emitted light is focused by glass lenses onto human retinahuman retina
Allows mapping distribution of a specific Allows mapping distribution of a specific protein in cellprotein in cell
12Cell Structure Cell Structure and Functionand Functionsciencescience
focusfocusMicroscopy Today:Microscopy Today:Confocal MicroscopyConfocal Microscopy
Narrow laser beam scanned across Narrow laser beam scanned across transparent specimentransparent specimen
Beam is focused at a very thin planeBeam is focused at a very thin plane
Allows microscopist to optically section a Allows microscopist to optically section a specimenspecimen
Sections made at different levelsSections made at different levels
Allows assembly of 3d image on computer Allows assembly of 3d image on computer screen that can be rotatedscreen that can be rotated
13Cell Structure Cell Structure and Functionand Functionsciencescience
focusfocusMicroscopy Today:Microscopy Today:Video-enhanced Contrast MicroscopyVideo-enhanced Contrast Microscopy
Great for specimens with low contrast, like Great for specimens with low contrast, like living cellsliving cells
Image is captured by TV camera instead of Image is captured by TV camera instead of eyeeye
Image is then “tweaked” by adjusting contrastImage is then “tweaked” by adjusting contrastDarkest part of image is made blackDarkest part of image is made blackLightest part of image is made whiteLightest part of image is made whiteAll parts in between made shades of grayAll parts in between made shades of gray
Also allows various shades to be converted to Also allows various shades to be converted to different colors for more contrastdifferent colors for more contrast
14Cell Structure Cell Structure and Functionand Functionsciencescience
focusfocusMicroscopy Today:Microscopy Today:Phase Contrast MicroscopyPhase Contrast Microscopy
Great for transparent specimens with low Great for transparent specimens with low contrast, like living cellscontrast, like living cells
Some organelles have higher density than Some organelles have higher density than othersothersSpeed of light is affected by densitySpeed of light is affected by densityLight passes more slowly through high Light passes more slowly through high density than low densitydensity than low density
Light waves entering a specimen “in phase” Light waves entering a specimen “in phase” exit some parts of the specimen out of phaseexit some parts of the specimen out of phase
Microscope shows only light that is slower or Microscope shows only light that is slower or fasterfaster
Causes transparent organelles to “glow”Causes transparent organelles to “glow”
15Microscopy and Amoeba proteus
16Microscopy and Cheek Cells
17Cell Structure Cell Structure and Functionand FunctionProkaryotic Cells:Prokaryotic Cells:
DomainsDomains
Lack a membrane-bound nucleusLack a membrane-bound nucleus
Structurally simpleStructurally simple
Two domains:Two domains:BacteriaBacteria Three ShapesThree Shapes
BacillusBacillus (rod) (rod) CoccusCoccus (spherical) (spherical) SpirillaSpirilla (spiral) (spiral)
ArchaeaArchaea Live in extreme habitatsLive in extreme habitats
18Shapes of Bacterial Cells
19Prokaryotic Cells: Visual Summary
20Cell Structure Cell Structure and Functionand FunctionProkaryotic Cells:Prokaryotic Cells:
The EnvelopeThe Envelope
Cell EnvelopesCell EnvelopesGlycocalyxGlycocalyx Layer of Layer of polysaccharidespolysaccharides outside cell wall outside cell wall
May be slimy and easily removed, orMay be slimy and easily removed, or
Well organized and resistant to removal Well organized and resistant to removal ((capsulecapsule))
Cell wallCell wallPlasma membranePlasma membrane Like in eukaryotesLike in eukaryotes
Form internal pouches (Form internal pouches (mesosomesmesosomes))
21Cell Structure Cell Structure and Functionand FunctionProkaryotic Cells:Prokaryotic Cells:
Cytoplasm & AppendagesCytoplasm & Appendages
CytoplasmCytoplasmSemifluid solutionSemifluid solution Bounded by plasma membraneBounded by plasma membrane Contains Contains inclusion bodiesinclusion bodies – Stored granules of – Stored granules of various substancesvarious substances
AppendagesAppendagesFlagellaFlagella – Provide motility – Provide motilityFimbriaeFimbriae – small, bristle-like fibers that sprout – small, bristle-like fibers that sprout from the cell surfacefrom the cell surface
Sex piliSex pili – rigid tubular structures used to pass – rigid tubular structures used to pass DNA from cell to cellDNA from cell to cell
22Cell Structure Cell Structure and Functionand Function
Eukaryotic CellsEukaryotic Cells
Domain Domain EukaryaEukaryaProtistsProtists
FungiFungi
PlantsPlants
AnimalsAnimals
Cells contain:Cells contain:Membrane-bound nucleusMembrane-bound nucleus
Specialized organellesSpecialized organelles
Plasma membranePlasma membrane
23Cell Structure Cell Structure and Functionand FunctionEukaryotic Cells :Eukaryotic Cells :
OrganellesOrganelles
Compartmentalization:Compartmentalization:Allows eukaryotic cells to be larger than Allows eukaryotic cells to be larger than prokaryotic cellsprokaryotic cells
Isolates reactions from othersIsolates reactions from othersTwo classes:Two classes:
Endomembrane system:Endomembrane system: Organelles that communicate with one anotherOrganelles that communicate with one another
via membrane channelsvia membrane channels Via small vesiclesVia small vesicles
Energy related organellesEnergy related organelles Mitochondria & chloroplastsMitochondria & chloroplasts Basically independent & self-sufficientBasically independent & self-sufficient
24Plasma Membrane
25Hypothesized Origin of Eukaryotic Cells
26Cell Structure Cell Structure and Functionand Functionsciencescience
focusfocusCell Fractionation, andCell Fractionation, andDifferential CentrifugationDifferential Centrifugation
Cell fractionationCell fractionation is the breaking apart of is the breaking apart of cellular componentscellular components
Differential centrifugationDifferential centrifugation::
Allows separation of cell partsAllows separation of cell parts
Separated out by size & densitySeparated out by size & density
Works like spin cycle of washerWorks like spin cycle of washer
The faster the machine spins, the The faster the machine spins, the smaller the parts that settled outsmaller the parts that settled out
2727ScienceScienceFocusFocus
Cell Fractionation, andCell Fractionation, andDifferential Differential
CentrifugationCentrifugationGrindcells
Centrifuge@ 600 g
Sedimentcontains
nuclei
Sedimentcontains
nuclei
Thencentrifuge
longer@ 15,000 g
Sedimentcontains
mitochondria,lysosomes
Sedimentcontains
mitochondria,lysosomes
Thencentrifuge
even longer@ 100,000 g
Sedimentcontains
ribosomes,ER
Sedimentcontains
ribosomes,ER
Solubleportion of
cytoplasm.No
sediment
Solubleportion of
cytoplasm.No
sediment
Figure4C
28Animal Cell Anatomy
29Plant Cell Anatomy
30Cell Structure Cell Structure and Functionand Function
NucleusNucleus
Command center of cell, usually near centerCommand center of cell, usually near centerSeparated from cytoplasm by Separated from cytoplasm by nuclear nuclear
envelopeenvelopeConsists of double layer of membraneConsists of double layer of membraneNuclear poresNuclear pores permit exchange between permit exchange between nucleoplasmnucleoplasm & cytoplasm & cytoplasm
Contains Contains chromatinchromatin in semifluid nucleoplasm in semifluid nucleoplasmChromatin contains Chromatin contains DNADNA of of genesgenesCondenses to form Condenses to form chromosomeschromosomes
Dark Dark nucleolusnucleolus composed of composed of rRNArRNAProduces subunits of Produces subunits of ribosomesribosomes
31Anatomy of the Nucleus
32Cell Structure Cell Structure and Functionand Function
RibosomesRibosomes
Serve in protein synthesisServe in protein synthesis
Composed of Composed of rRNArRNA
Consists of a Consists of a largelarge subunitsubunit and a and a smallsmall subunitsubunit
Subunits made in nucleolusSubunits made in nucleolus
May be located:May be located:
On the endoplasmic reticulum (thereby On the endoplasmic reticulum (thereby making it “rough”), ormaking it “rough”), or
Free in the cytoplasm, either singly or in Free in the cytoplasm, either singly or in groups called groups called polyribosomespolyribosomes
33Nucleus, Ribosomes, & ER
Figure4.9
34Cell Structure Cell Structure and Functionand Function
Endomembrane SystemEndomembrane System
Restrict enzymatic reactions to specific Restrict enzymatic reactions to specific compartments within cellcompartments within cell
Consists of:Consists of:Nuclear envelopeNuclear envelope
Membranes of Membranes of endoplasmic reticulumendoplasmic reticulum
Golgi apparatusGolgi apparatus
VesiclesVesicles
Several typesSeveral types
Transport materials between organelles of Transport materials between organelles of systemsystem
35Cell Structure Cell Structure and Functionand FunctionEndomembrane System:Endomembrane System:
The Endoplasmic ReticulumThe Endoplasmic Reticulum
Rough ERRough ERStudded with ribosomes on cytoplasmic sideStudded with ribosomes on cytoplasmic sideProtein anabolismProtein anabolism Synthesizes proteinsSynthesizes proteins
Modifies proteinsModifies proteins Adds sugar to proteinAdds sugar to protein Results in Results in glycoproteinsglycoproteins
Smooth ERSmooth ERNo ribosomesNo ribosomesSynthesis of Synthesis of lipidslipids
36Endoplasmic Reticulum
37Golgi Apparatus
38Lysosomes
39Cell Structure Cell Structure and Functionand FunctionEndomembrane System:Endomembrane System:
The Golgi ApparatusThe Golgi Apparatus
Golgi ApparatusGolgi ApparatusConsists of 3-20 flattened, curved sacculesConsists of 3-20 flattened, curved saccules
Resembles stack of hollow pancakesResembles stack of hollow pancakes
Modifies proteins and lipidsModifies proteins and lipids
Packages them in vesiclesPackages them in vesicles
Receives vesicles from ER on Receives vesicles from ER on cis facecis face
Prepares for “shipment” in vesicles from Prepares for “shipment” in vesicles from trans trans faceface Within cellWithin cell Export from cell (Export from cell (secretionsecretion, , exocytosisexocytosis))
40Cell Structure Cell Structure and Functionand FunctionEndomembrane System:Endomembrane System:
LysosomesLysosomes
Membrane-bound vesicles (not in plants)Membrane-bound vesicles (not in plants)Produced by the Golgi apparatusProduced by the Golgi apparatusLow pHLow pHContain Contain lyticlytic enzymes enzymes Digestion of large moleculesDigestion of large molecules Recycling of cellular resourcesRecycling of cellular resources ApoptosisApoptosis (programmed cell death, like tadpole (programmed cell death, like tadpole losing tail)losing tail)
Some genetic diseasesSome genetic diseasesCaused by defect in lysosomal enzymeCaused by defect in lysosomal enzymeLysosomal storage diseasesLysosomal storage diseases ( (Tay-SachsTay-Sachs))
41Endomembrane System: A Visual Summary
42Cell Structure Cell Structure and Functionand Function
PeroxisomesPeroxisomes
Similar to lysosomesSimilar to lysosomesMembrane-bounded vesiclesMembrane-bounded vesiclesEnclose enzymesEnclose enzymes
HoweverHoweverEnzymes synthesized by free ribosomes in Enzymes synthesized by free ribosomes in cytoplasm (instead of ER)cytoplasm (instead of ER)
Active in lipid metabolismActive in lipid metabolismCatalyzeCatalyze reactions that produce reactions that produce hydrogen hydrogen peroxide Hperoxide H22OO22
ToxicToxic Broken down to water & OBroken down to water & O22 by by catalasecatalase
43Peroxisomes
44Cell Structure Cell Structure and Functionand Function
VacuolesVacuoles
Membranous sacs that are larger than Membranous sacs that are larger than vesiclesvesiclesStore materials that occur in excessStore materials that occur in excessOthers very specialized (Others very specialized (contractile vacuolecontractile vacuole))
Plants cells typically have a Plants cells typically have a central vacuolecentral vacuoleUp to 90% volume of some cellsUp to 90% volume of some cellsFunctions in:Functions in: Storage of water, nutrients, pigments, and Storage of water, nutrients, pigments, and waste productswaste products Development of Development of turgorturgor pressure pressure Some functions performed by lysosomes in Some functions performed by lysosomes in other eukaryotesother eukaryotes
45Vacuoles
46Cell Structure Cell Structure and Functionand FunctionEnergy-Related Organelles:Energy-Related Organelles:
Chloroplast StructureChloroplast Structure
Bounded by double membraneBounded by double membrane
Inner membrane infoldedInner membrane infolded
Forms disc-like Forms disc-like thylakoidsthylakoids, which are stacked , which are stacked to formto form granagrana
Suspended in semi-fluid Suspended in semi-fluid stromastroma
Green due to Green due to chlorophyllchlorophyll
Green photosynthetic pigmentGreen photosynthetic pigment
Found ONLY in inner membranes of Found ONLY in inner membranes of chloroplastchloroplast
47Cell Structure Cell Structure and Functionand FunctionEnergy-Related Organelles:Energy-Related Organelles:
ChloroplastsChloroplasts
Captures light energy to drive cellular Captures light energy to drive cellular machinerymachinery
PhotosynthesisPhotosynthesis
Synthesizes carbohydrates from COSynthesizes carbohydrates from CO22 & H & H22OO
Makes own food using COMakes own food using CO22 as only carbon as only carbon sourcesource
Energy-poor compounds converted to enery Energy-poor compounds converted to enery rich compoundsrich compounds
48Energy-Related Organelles:
Chloroplast Structure
49Cell Structure Cell Structure and Functionand FunctionEnergy-Related Organelles:Energy-Related Organelles:
MitochondriaMitochondria
Bounded by double membraneBounded by double membrane
CristaeCristae – Infoldings of inner membrane that – Infoldings of inner membrane that encloses matrixencloses matrix
MatrixMatrix – Inner semifluid containing respiratory – Inner semifluid containing respiratory enzymesenzymes
Involved in Involved in cellular respirationcellular respiration
Produce most of Produce most of ATPATP utilized by the cell utilized by the cell
50Energy-Related Organelles:
Mitochondrial Structure
51Cell Structure Cell Structure and Functionand Function
The The CytoskeletonCytoskeleton
Maintains cell shapeMaintains cell shape
Assists in movement of cell and organellesAssists in movement of cell and organelles
Three types of macromolecular fibersThree types of macromolecular fibers
ActinActin FilamentsFilaments
Intermediate FilamentsIntermediate Filaments
MicrotubulesMicrotubules
Assemble and disassemble as neededAssemble and disassemble as needed
52Cell Structure Cell Structure and Functionand FunctionThe Cytoskeleton:The Cytoskeleton:
Actin FilamentsActin Filaments
Extremely thin filaments like twisted pearl Extremely thin filaments like twisted pearl necklacenecklace
Dense web just under plasma membrane Dense web just under plasma membrane maintains cell shapemaintains cell shape
Support for Support for microvillimicrovilli in intestinal cells in intestinal cellsIntracellular traffic controlIntracellular traffic control
For moving stuff around within cellFor moving stuff around within cellCytoplasmic streamingCytoplasmic streaming
Function in Function in pseudopodspseudopods of of amoeboidamoeboid cells cellsPinch mother cell in two after animal Pinch mother cell in two after animal mitosismitosisImportant component in muscle contraction Important component in muscle contraction
(other is (other is myosinmyosin))
53The Cytoskeleton:Actin Filament
Operation
54Cell Structure Cell Structure and Functionand FunctionThe Cytoskeleton:The Cytoskeleton:
Intermediate FilamentsIntermediate Filaments
Intermediate in size between actin filaments Intermediate in size between actin filaments and microtubulesand microtubules
Rope-like assembly of fibrous Rope-like assembly of fibrous polypeptidespolypeptides
Vary in natureVary in natureFrom tissue to tissueFrom tissue to tissue
From time to timeFrom time to time
Functions:Functions:Support nuclear envelopeSupport nuclear envelope
Cell-cell junctions, like those holding skin Cell-cell junctions, like those holding skin cells tightly togethercells tightly together
55Cell Structure Cell Structure and Functionand FunctionThe Cytoskeleton:The Cytoskeleton:
MicrotubulesMicrotubules
Hollow cylinders made of two Hollow cylinders made of two globular globular proteinsproteins called called and tubulintubulin
Spontaneous pairing of Spontaneous pairing of and and tubulin tubulin molecules form structures called molecules form structures called dimersdimers
Dimers then arrange themselves into tubular Dimers then arrange themselves into tubular spirals of 13 dimers aroundspirals of 13 dimers around
Assembly:Assembly:Under control of Under control of Microtubule Organizing Microtubule Organizing CenterCenter ( (MTOCMTOC))
Most important MTOC is Most important MTOC is centrosomecentrosomeInteracts with proteins Interacts with proteins kinesinkinesin and and dyneindynein to to
cause movement of organellescause movement of organelles
56The Cytoskeleton:Microtubule Operation
57Cell Structure Cell Structure and Functionand FunctionMicrotubular Arrays:Microtubular Arrays:
CentriolesCentrioles
Short, hollow cylindersShort, hollow cylindersComposed of 27 microtubulesComposed of 27 microtubulesMicrotubules arranged into 9 overlapping Microtubules arranged into 9 overlapping tripletstriplets
One pair per animal cellOne pair per animal cellLocated in Located in centrosomecentrosome of animal cells of animal cellsOriented at right angles to each otherOriented at right angles to each otherSeparate during mitosis to determine plane of Separate during mitosis to determine plane of divisiondivision
May give rise to May give rise to basal bodiesbasal bodies of of ciliacilia and and flagellaflagella
58Cytoskeleton:
Centrioles
59Cell Structure Cell Structure and Functionand FunctionMicrotubular arrays:Microtubular arrays:
Cilia and FlagellaCilia and Flagella
Hair-like projections from cell surface that aid Hair-like projections from cell surface that aid in cell movementin cell movement
Very different from prokaryote flagellaVery different from prokaryote flagellaOuter covering of plasma membraneOuter covering of plasma membrane Inside this is a cylinder of 18 microtubules Inside this is a cylinder of 18 microtubules arranged in 9 pairsarranged in 9 pairs
In center are two single microtubulesIn center are two single microtubulesThis This 9 + 2 pattern9 + 2 pattern used by all cilia & flagella used by all cilia & flagella
In eukaryotes, cilia are much shorter than In eukaryotes, cilia are much shorter than flagellaflagellaCilia move in coordinated waves like oarsCilia move in coordinated waves like oarsFlagella move like a propeller or cork screwFlagella move like a propeller or cork screw
60Structure of a Flagellum
61Cell Structure Cell Structure and Functionand Function
ReviewReview
Cell TheoryCell Theory
Cell SizeCell Size
Prokaryotic CellsProkaryotic Cells
Eukaryotic CellsEukaryotic CellsOrganellesOrganelles
NucleusNucleus
Endomembrane SystemEndomembrane System
CytoskeletonCytoskeleton
Centrioles, Cilia, and FlagellaCentrioles, Cilia, and Flagella
Cell Structure and Function
Ending Slide Chapter 04
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