Ch. 4 Outline – Cell Structure & Function

1Cell Structure Cell Structure and Functionand Function

Ch. 4 Outline – Cell Structure & FunctionCh. 4 Outline – Cell Structure & Function


Cell TheoryCell Theory

A unifying concept in biologyA unifying concept in biology

States that:States that:All organisms are composed of cellsAll organisms are composed of cellsMatthais Schleiden in 1838Matthais Schleiden in 1838

Theodor Schwann in 1839Theodor Schwann in 1839All cells come only from preexisting cellsAll cells come only from preexisting cells Rudolph Virchow in 1850’sRudolph Virchow in 1850’s

Smallest unit of lifeSmallest unit of life

3Organisms and Cells

4Sizes of Living Things


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

6Surface to Volume RatioSurface to Volume Ratio

Total Surface Area96cm2 192cm2 384cm2

Total Volume64cm3 64cm3 64cm3

Surface Area Per Cube / Volume Per Cube1.5:1 3:1 6:1

Total Surface Area96cm2 192cm2 384cm2

Total Volume64cm3 64cm3 64cm3

Surface Area Per Cube / Volume Per Cube1.5:1 3:1 6:1

7MicroscopyVocabularyMicroscopyVocabulary

1. 1. MagnificationMagnificationa.Howmuchlargertheobjecta.Howmuchlargertheobject appearscomparedtorealappearscomparedtoreal

sizesize

82.Resolving2.Resolving

powerpower a.Measureofclarityofimagea.Measureofclarityofimageb.Minimumdistancetwopointscanb.Minimumdistancetwopointscan

beseparatedandstillbebeseparatedandstillbe distinguishedastwoseparatepointsdistinguishedastwoseparatepoints

vs

9Cell 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


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 1,000,000 XMax magnification 1,000,000 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


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


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 light) passed through Ultra-violet light (black light) 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 Emitted light is focused by glass lenses Allows mapping distribution of a specific Allows mapping distribution of a specific

protein in cellprotein in cell


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


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


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”

16Microscopy and Amoeba proteus

17Microscopy and Cheek Cells

18Cell 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

19Shapes of Bacterial Cells

20Prokaryotic Cells: Visual Summary


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))


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


Eukaryotic CellsEukaryotic Cells

Domain Domain EukaryaEukaryaProtistsProtists

FungiFungi

PlantsPlants

AnimalsAnimals

Cells contain:Cells contain:Membrane-bound nucleusMembrane-bound nucleus

Specialized organellesSpecialized organelles

Plasma membranePlasma membrane

24Cell Structure Cell Structure and Functionand FunctionEukaryotic Cells :Eukaryotic Cells :

OrganellesOrganelles

CompartmentalizationCompartmentalization: : 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 systemEndomembrane 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 organellesMitochondria & chloroplastsMitochondria & chloroplasts Basically independent & self-sufficientBasically independent & self-sufficient

25Plasma Membrane

26Hypothesized Origin of Eukaryotic Cells

Endosymbiosis


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 smaller the The faster the machine spins, the smaller the parts that settled outparts that settled out

2828ScienceScienceFocusFocus

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

29Animal Cell Anatomy

30Plant Cell Anatomy


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

32Anatomy of the Nucleus


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

34Nucleus, Ribosomes, & ER

Figure4.9


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

36Endomembrane System: A Visual Summary

37Cell 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

38Endoplasmic Reticulum


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))

40Golgi Apparatus


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))

42Lysosomes


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

44Peroxisomes


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

46Vacuoles

47Endomembrane System: A Visual Summary

48Cell Structure Cell Structure and Functionand FunctionEnergy-Related Organelles:Energy-Related Organelles:

Chloroplast StructureChloroplast Structure

Bounded by double membraneBounded by double membrane

Inner membrane not foldedInner membrane not folded

Disc-like Disc-like thylakoidsthylakoids are stacked to form are stacked to 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 membranes of thylakoids of Found ONLY in membranes of thylakoids of chloroplastchloroplast


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 energy Energy-poor compounds converted to energy rich compoundsrich compounds

50Energy-Related Organelles:

Chloroplast Structure


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

52Energy-Related Organelles:

Mitochondrial Structure


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

54Cell 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))

55The Cytoskeleton:Actin Filament

Operation


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


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

58The Cytoskeleton:Microtubule Operation

59Cell 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

60Cytoskeleton:

Centrioles

61Cell 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

62Structure of a Flagellum

63

Video: The Inner Life of a Cell

http://multimedia.mcb.harvard.edu/ahttp://multimedia.mcb.harvard.edu/anim_innerlife_Hi.htmlnim_innerlife_Hi.html

http://multimedia.mcb.harvard.edu/anim_innerlife_Hi.html

http://multimedia.mcb.harvard.edu/anim_innerlife_Hi.html

Ch. 4 Outline – Cell Structure & Function

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