Chapter 6: A Tour of the Cell. The Beginning Hooke’sMicroscope First Cells - 1665 Leeuwenhoek’sMicroscope First Living Cells - 1674.

Chapter 6:Chapter 6:

A Tour of the CellA Tour of the Cell

The BeginningThe Beginning

Hooke’sHooke’s

MicroscopeMicroscope

First Cells - 1665First Cells - 1665

LeeuwenhoekLeeuwenhoek’s’s

MicroscopeMicroscope

First First Living Living Cells - 1674Cells - 1674

Studying CellsStudying Cells

• MicroscopesMicroscopes

• LightLight

• ElectronElectron

• Cell FractionationCell Fractionation

The Light MicroscopeThe Light Microscope

• Light is transmitted through the specimenLight is transmitted through the specimen

• Magnified and focused using lensesMagnified and focused using lenses

• Maximum magnification is around 1000XMaximum magnification is around 1000X

• Sample can be stained to see various Sample can be stained to see various organelles and internal structuresorganelles and internal structures

• Can look at preserved or living specimensCan look at preserved or living specimens

The Light MicroscopeThe Light Microscope• Light is transmitted through the Light is transmitted through the

specimenspecimen

• Magnified and focused using lensesMagnified and focused using lenses

• Maximum magnification is around Maximum magnification is around 1000X1000X

• Sample can be stained to see Sample can be stained to see various organelles and internal various organelles and internal structuresstructures

• Can view preserved or living Can view preserved or living specimensspecimens

Micrograph from Light MicroscopeMicrograph from Light Microscope

EuglenaEuglena, LM , LM 1000X1000X

ResolutionResolution

The Electron MicroscopeThe Electron Microscope

• Two types: Scanning (SEM) and Two types: Scanning (SEM) and Transmission (TEM)Transmission (TEM)

• Electrons are passed through the Electrons are passed through the specimen (TEM) or bounce off the specimen (TEM) or bounce off the surface (SEM)surface (SEM)

• Maximum magnification is around Maximum magnification is around 100,000X100,000X

• High resolutionHigh resolution

• All specimens MUST BE preserved – All specimens MUST BE preserved – no living cellsno living cells

Micrograph from Transmission Micrograph from Transmission Electron MicroscopeElectron Microscope

Figure 6.8bc

1 m

Cell wall

Vacuole

Nucleus

Mitochondrion

A single yeast cell(colorized TEM)

Micrograph from Scanning Micrograph from Scanning Electron MicroscopeElectron Microscope

Fig. 6-5

Cell FractionationCell Fractionation

• Technique used to separate Technique used to separate organelles and major structures organelles and major structures from one anotherfrom one another

• Involves centrifugationInvolves centrifugation

• Heavier components are pushed Heavier components are pushed to the bottom of the test tubeto the bottom of the test tube

• Can separate out using Can separate out using sequential centrifugations at sequential centrifugations at increasing speedsincreasing speeds

TECHNIQUE

Homogenization

Tissuecells

Homogenate

Centrifugation

Differentialcentrifugation

Centrifuged at1,000 g

(1,000 times theforce of gravity)

for 10 min Supernatantpoured intonext tube

20,000 g20 min

80,000 g60 min

Pellet rich innuclei andcellular debris

150,000 g3 hr

Pellet rich inmitochondria(and chloro-plasts if cellsare from a plant)

Pellet rich in“microsomes”(pieces of plasmamembranes andcells’ internalmembranes) Pellet rich in

ribosomes

Cell TheoryCell Theory

1.1. All organisms are made of All organisms are made of cellscells

2.2. All cells come from cellsAll cells come from cells

Features of All CellsFeatures of All Cells

1.1. Plasma membrane - selective barrier Plasma membrane - selective barrier

2.2. Cytoplasm – semifluid substance Cytoplasm – semifluid substance containing organelles and other containing organelles and other componentscomponents

3.3. DNA – genetic informationDNA – genetic information

4.4. Ribosomes – protein making structuresRibosomes – protein making structures

Prokaryotes vs. EukaryotesProkaryotes vs. Eukaryotes• DNA Location:DNA Location:

• Proks: nucleoid regionProks: nucleoid region

• Euks: nucleusEuks: nucleus

• OrganellesOrganelles

• Proks: no true organelles (no Proks: no true organelles (no internal membranes)internal membranes)

• Euks: membrane-bound Euks: membrane-bound organellesorganelles

• SizeSize

• Proks: smallerProks: smaller

• Euks: largerEuks: larger

Nucleoidregion

Prokaryotic cell

Nucleus

Co

lor i

z ed

TE

M 1

5, 0

00

Eukaryotic cellOrganelles

Fig. 6-8

Surface area increases whiletotal volume remains constant

5

11

6 150 750

125 1251

6 61.2

Total surface area

[Sum of the surface areas

(height width) of all

boxes

sides number of boxes]Total volume

[height width length number of boxes]

Surface-to-volume

(S-to-V) ratio

[surface area ÷ volume]

Does size matter?Does size matter?

Fig. 6-6

Fimbriae

Nucleoid

Ribosomes

Plasma membrane

Cell wall

Capsule

Flagella

Bacterialchromosome

(a) A typical rod-shaped bacterium

(b) A thin section through the bacterium Bacillus coagulans (TEM)

0.5 µm

Features of Prokaryotic CellsFeatures of Prokaryotic Cells

Organisms with eukaryotic cellsOrganisms with eukaryotic cells

1.1. AnimalsAnimals

2.2. PlantsPlants

3.3. FungiFungi

4.4. ProtistsProtists

Anim

al C

ell

Anim

al C

ell

Figure 6.8aENDOPLASMIC RETICULUM (ER)

RoughER

SmoothER

Nuclearenvelope

Nucleolus

Chromatin

Plasmamembrane

Ribosomes

Golgi apparatus

LysosomeMitochondrion

Peroxisome

Microvilli

MicrotubulesIntermediate filaments

Microfilaments

Centrosome

CYTOSKELETON:

Flagellum NUCLEUS

Pla

nt

Cell

Pla

nt

Cell

Figure 6.8c

NUCLEUS

Nuclearenvelope

Nucleolus

Chromatin

Golgiapparatus

Mitochondrion

Peroxisome

Plasma membrane

Cell wall

Wall of adjacent cell

Plasmodesmata

Chloroplast

Microtubules

Intermediatefilaments

Microfilaments

CYTOSKELETON

Central vacuole

Ribosomes

Smoothendoplasmicreticulum

Roughendoplasmic

reticulum

Features Found in Plant Cells, but Features Found in Plant Cells, but NOT Animal CellsNOT Animal Cells

1.1. Cell WallCell Wall

2.2. ChloroplastChloroplast

3.3. Central vacuoleCentral vacuole

4.4. PlasmodesmataPlasmodesmata

Features Found in Animal Cells, Features Found in Animal Cells, but NOT Plant Cellsbut NOT Plant Cells

1.1. LysosomesLysosomes

2.2. CentrosomesCentrosomes

3.3. FlagellaFlagella

Fig. 6-10

NucleolusNucleus

Rough ER

Nuclear lamina (TEM)

Close-up of nuclear envelope

1 µm

1 µm

0.25 µm

Ribosome

Pore complex

Nuclear pore

Outer membraneInner membraneNuclear envelope:

Chromatin

Surface ofnuclear envelope

Pore complexes (TEM)

Nucl

eus

Nucl

eus

Fig. 6-11

Cytosol

Endoplasmic reticulum (ER)

Free ribosomes

Bound ribosomes

Large subunit

Small subunit

Diagram of a ribosomeTEM showing ER and ribosomes

0.5 µm

Rib

oso

me

Rib

oso

me

Transport vesiclefrom ER to GolgiRough ER

Nucleus

Smooth ER Nuclear envelope Golgi apparatus

Lysosome

Vacuole

Plasmamembrane

Transport vesicle fromGolgi to plasma membrane

Endomembrane System: Endomembrane System: OverviewOverview

Fig. 6-12Smooth ER

Rough ER Nuclear envelope

Transitional ER

Rough ERSmooth ERTransport vesicle

RibosomesCisternaeER lumen

200 nm

Endoplasmic Endoplasmic Reticulum Reticulum

(ER)(ER)

Smooth ERSmooth ER

Three functions of the Smooth Three functions of the Smooth ER:ER:

1.1. Lipid productionLipid production

2.2. Detoxifying enzymesDetoxifying enzymes

3.3. Calcium ion storageCalcium ion storage

Rough ERRough ER

Two functions of the Rough ER:Two functions of the Rough ER:

1.1. Membrane productionMembrane production

2.2. Along with ribosomes, produce proteins for Along with ribosomes, produce proteins for use within the endomembrane system or use within the endomembrane system or for secretion from the cellfor secretion from the cell

3.3. Protein modificationProtein modification

Transport vesiclebuds off

Ribosome

Polypeptide

Glycoprotein

Sugarchain

Rough ER

Secretary(glyco-) proteininside trans-port vesicle

Figure 6.12

cis face(“receiving” side ofGolgi apparatus)

trans face(“shipping” side ofGolgi apparatus)

0.1 m

TEM of Golgi apparatus

Cisternae

Golgi Apparatus (Golgi Complex)Golgi Apparatus (Golgi Complex)

Figure 6.13

Nucleus

Lysosome

1 m

Digestiveenzymes

Digestion

Food vacuole

LysosomePlasma membrane

(a) Phagocytosis

Vesicle containingtwo damagedorganelles

1 m

Mitochondrionfragment

Peroxisomefragment

(b) Autophagy

Peroxisome

VesicleMitochondrion

Lysosome

Digestion

LysosomeLysosome

Figure 6.14

Central vacuole

Cytosol

Nucleus

Cell wall

Chloroplast

Centralvacuole

5 m

Centr

al V

acu

ole

Centr

al V

acu

ole

Figure 6.15-1

Smooth ER

Nucleus

Rough ER

Plasmamembrane

Figure 6.15-2

Smooth ER

Nucleus

Rough ER

Plasmamembrane

cis Golgi

trans Golgi

Figure 6.15-3

Smooth ER

Nucleus

Rough ER

Plasmamembrane

cis Golgi

trans Golgi

Mitochondria: Powerhouse of the Mitochondria: Powerhouse of the CellCell

• Mitochondria are divided into two Mitochondria are divided into two compartments (separated by the compartments (separated by the innerinnermembrane):membrane):

1.1. InterIntermembrane spacemembrane space

2.2. Mitochondrial matrixMitochondrial matrix

Figure 6.16NucleusEndoplasmic

reticulum

Nuclear envelope

Ancestor ofeukaryotic cells(host cell)

Engulfing of oxygen-using nonphotosyntheticprokaryote, whichbecomes a mitochondrion

Mitochondrion

Nonphotosyntheticeukaryote

Mitochondrion

At leastone cell

Photosynthetic eukaryote

Engulfing ofphotosyntheticprokaryote

Chloroplast

Figure 6.17

Intermembrane space

Outermembrane

DNA

Innermembrane

Cristae

Matrix

Freeribosomesin themitochondrialmatrix

(a) Diagram and TEM of mitochondrion (b) Network of mitochondria in a protistcell (LM)

0.1 m

MitochondrialDNA

Nuclear DNA

Mitochondria

10 m

Mitochondria: Powerhouse of the Mitochondria: Powerhouse of the CellCell

Chloroplasts: Site of Chloroplasts: Site of PhotosynthesisPhotosynthesis

• Converts solar energy into chemical energyConverts solar energy into chemical energy

• Chloroplasts are divided into three Chloroplasts are divided into three compartments:compartments:

1.1. Intermembrane spaceIntermembrane space

2.2. StromaStroma

3.3. GranaGrana

Figure 6.18

RibosomesStroma

Inner and outermembranes

Granum

1 mIntermembrane spaceThylakoid

(a) Diagram and TEM of chloroplast (b) Chloroplasts in an algal cell

Chloroplasts(red)

50 m

DNA

Chloroplasts: Site of Chloroplasts: Site of PhotosynthesisPhotosynthesis

Figure 6.19

ChloroplastPeroxisome

Mitochondrion

1 m

PeroxisomePeroxisome

CytoskeletonCytoskeleton

• Microfilaments – Microfilaments – thinnestthinnest

• Intermediate Intermediate filamentsfilaments

• Microtubules – Microtubules – thickestthickest

Figure 6.20

10

m

CytoskeletonCytoskeleton

• Microfilaments – Microfilaments – thinnestthinnest

• Intermediate Intermediate filamentsfilaments

• Microtubules – Microtubules – thickestthickest

Table 6.1

Column of tubulin dimers

Tubulin dimer

25 nm

Actin subunit

7 nm

Keratin proteins

812 nm

Fibrous subunit (keratinscoiled together)

10 m 10 m 5 m

Figure 6.23

Direction of swimming

(b) Motion of cilia

Direction of organism’s movement

Power stroke Recovery stroke

(a) Motion of flagella5 m

15 m

Cili

a a

nd F

lagella

Cili

a a

nd F

lagella

Fig. 6-24

0.1 µm

Triplet

(c) Cross section of basal body

(a) Longitudinal section of cilium

0.5 µm

Plasma membrane

Basal body

Microtubules

(b) Cross section of cilium

Plasma membrane

Outer microtubule doublet

Dynein proteins

Central microtubuleRadial spoke

Protein cross-linking outer doublets

0.1 µm

Fig. 6-28

Secondary cell wall

Primary cell wall

Middle lamella

Central vacuoleCytosol

Plasma membrane

Plant cell walls

Plasmodesmata

1 µm

Fig. 6-30

EXTRACELLULAR FLUIDCollagen

Fibronectin

Plasmamembrane

Micro-filaments

CYTOPLASM

Integrins

Proteoglycancomplex

Polysaccharidemolecule

Carbo-hydrates

Coreprotein

Proteoglycanmolecule

Proteoglycan complex

Fig. 6-32

Tight junction

0.5 µm

1 µmDesmosome

Gap junction

Extracellularmatrix

0.1 µm

Plasma membranesof adjacent cells

Spacebetweencells

Gapjunctions

Desmosome

Intermediatefilaments

Tight junction

Tight junctions preventfluid from movingacross a layer of cells

Figure 6.UN01

Nucleus

(ER)

(Nuclearenvelope)