Cell Structure and FunctionCell Structure and Function

Chapter 4Chapter 4

Mid 1600s - Robert Hooke observed Mid 1600s - Robert Hooke observed

and described cells in corkand described cells in cork

Late 1600s - Antony van Late 1600s - Antony van

Leeuwenhoek observed sperm, Leeuwenhoek observed sperm,

microorganismsmicroorganisms

1820s - Robert Brown observed and 1820s - Robert Brown observed and

named nucleus in plant cellsnamed nucleus in plant cells

Early DiscoveriesEarly Discoveries

Developing Cell TheoryDeveloping Cell Theory

Matthias Schleiden Matthias Schleiden

Theodor Schwann Theodor Schwann

Rudolf Virchow Rudolf Virchow

Cell TheoryCell Theory

1) Every organism is composed of one 1) Every organism is composed of one

or more cellsor more cells

2) Cell is smallest unit having 2) Cell is smallest unit having

properties of lifeproperties of life

3) Continuity of life arises from growth 3) Continuity of life arises from growth

and division of single cellsand division of single cells

Smallest unit of lifeSmallest unit of life

Can survive on its own or has Can survive on its own or has

potential to do sopotential to do so

Is highly organized for metabolismIs highly organized for metabolism

Senses and responds to environmentSenses and responds to environment

Has potential to reproduceHas potential to reproduce

CellCell

Structure of CellsStructure of Cells

All start out life All start out life with:with:– Plasma Plasma

membrane membrane

– Region where Region where DNA is storedDNA is stored

– Cytoplasm Cytoplasm

Two types:Two types:– ProkaryoticProkaryotic

– Eukaryotic Eukaryotic

Main component of cell membranesMain component of cell membranes

Gives the membrane its fluid Gives the membrane its fluid propertiesproperties

Two layers of phospholipidsTwo layers of phospholipids

Lipid BilayerLipid Bilayer

one layerof lipids

one layerof lipids

Figure 4.3Page 56

Membrane ProteinsMembrane Proteins

Protein pump across

bilayer

Protein channel

across bilayer

Protein pump

Recognition protein

Receptor protein

extracellular environment

cytoplasm

lipid bilayer

Figure 4.4Page 57

Why Are Cells So Small?Why Are Cells So Small?

Surface-to-volume ratioSurface-to-volume ratio

The bigger a cell is, the less surface The bigger a cell is, the less surface

area there is per unit volumearea there is per unit volume

Above a certain size, material cannot Above a certain size, material cannot

be moved in or out of cell fast be moved in or out of cell fast

enoughenough

Create detailed images of something Create detailed images of something

that is otherwise too small to seethat is otherwise too small to see

Light microscopesLight microscopes– Simple or compoundSimple or compound

Electron microscopesElectron microscopes– Transmission EM or Scanning EMTransmission EM or Scanning EM

MicroscopesMicroscopes

Eukaryotic CellsEukaryotic Cells

Have a nucleus and Have a nucleus and other organellesother organelles

Eukaryotic organismsEukaryotic organisms– PlantsPlants– AnimalsAnimals– ProtistansProtistans– FungiFungi

Animal Cell FeaturesAnimal Cell Features

Plasma membranePlasma membrane

NucleusNucleus

RibosomesRibosomes

Endoplasmic Endoplasmic reticulumreticulum

Golgi bodyGolgi body

VesiclesVesicles

MitochondriaMitochondria

CytoskeletonCytoskeleton

Figure 4.10bPage 61

Plant Cell FeaturesPlant Cell Features

Cell wallCell wall

Central vacuoleCentral vacuole

ChloroplastChloroplast

Plasma membranePlasma membrane

NucleusNucleus

RibosomesRibosomes

Endoplasmic Endoplasmic reticulumreticulum

Golgi bodyGolgi body

VesiclesVesicles

MitochondriaMitochondria

CytoskeletonCytoskeleton

Figure 4.10aPage 61

Keeps the DNA molecules of Keeps the DNA molecules of eukaryotic cells separated from eukaryotic cells separated from metabolic machinery of cytoplasmmetabolic machinery of cytoplasm

Makes it easier to organize DNA and Makes it easier to organize DNA and to copy it before parent cells divide to copy it before parent cells divide into daughter cells into daughter cells

Functions of NucleusFunctions of Nucleus

Components of NucleusComponents of Nucleus

nuclear envelope

nucleoplasm

nucleolus

chromatin

Figure 4.11bPage 62

Nuclear EnvelopeNuclear Envelope

Two outer membranes (lipid bilayers)Two outer membranes (lipid bilayers)

Innermost surface has DNA attachment Innermost surface has DNA attachment sitessites

Nuclear pore bilayer facing cytoplasm Nuclear envelope

bilayer facing nucleoplasm

Figure 4.12bPage 63

Group of related organelles in which Group of related organelles in which lipids are assembled and new lipids are assembled and new polypeptide chains are modifiedpolypeptide chains are modified

Products are sorted and shipped to Products are sorted and shipped to various destinationsvarious destinations

Cytomembrane SystemCytomembrane System

Components of Cytomembrane Components of Cytomembrane SystemSystem

Endoplasmic reticulumEndoplasmic reticulum

Golgi bodiesGolgi bodies

VesiclesVesicles

Endoplasmic ReticulumEndoplasmic Reticulum

In animal cells, continuous with In animal cells, continuous with

nuclear membranenuclear membrane

Extends throughout cytoplasmExtends throughout cytoplasm

Two regions - rough and smoothTwo regions - rough and smooth

Golgi BodyGolgi Body

Puts finishing touches on proteins Puts finishing touches on proteins and lipids that arrive from ERand lipids that arrive from ER

Packages finished material for Packages finished material for shipment to final destinationsshipment to final destinations

Material arrives and leaves in vesiclesMaterial arrives and leaves in vesicles

budding vesicle

Figure 4.15Page 65

VesiclesVesicles

Membranous sacs that Membranous sacs that

move through move through

cytoplasmcytoplasm

LysosomesLysosomes

PeroxisomesPeroxisomes

ATP-producing powerhousesATP-producing powerhouses

Membranes form two distinct Membranes form two distinct

compartments compartments

ATP-making machinery embedded ATP-making machinery embedded

in inner mitochondrial membranein inner mitochondrial membrane

MitochondriaMitochondria

Mitochondrial OriginsMitochondrial Origins

Mitochondria resemble bacteriaMitochondria resemble bacteria

– Have own DNA, ribosomesHave own DNA, ribosomes

– Divide on their ownDivide on their own

May have evolved from ancient May have evolved from ancient bacteria that were engulfed but not bacteria that were engulfed but not digesteddigested

PlastidsPlastids

Central VacuoleCentral Vacuole

Specialized Plant OrganellesSpecialized Plant Organelles

ChloroplastsChloroplasts

Convert sunlight energy to ATP Convert sunlight energy to ATP through photosynthesisthrough photosynthesis

Other PlastidsOther Plastids

Chromoplasts Chromoplasts – No chlorophyllNo chlorophyll

– Abundance of carotenoidsAbundance of carotenoids

– Color fruits and flowers red to yellowColor fruits and flowers red to yellow

AmyloplastsAmyloplasts– No pigmentsNo pigments

– Store starchStore starch

Present in all eukaryotic cellsPresent in all eukaryotic cells

Basis for cell shape and internal Basis for cell shape and internal organizationorganization

Allows organelle movement within Allows organelle movement within cells and, in some cases, cell motilitycells and, in some cases, cell motility

CytoskeletonCytoskeleton

Flagella and CiliaFlagella and Cilia

Structures for Structures for

cell motilitycell motility

9 + 2 internal 9 + 2 internal

structurestructure

dynein

microtubule

Figure 4.25Page 73

Plant Cell WallsPlant Cell Walls

Primary cell wall

Secondary cell wall(3 layers)

Plant CuticlePlant Cuticle

Cell secretions and waxes Cell secretions and waxes accumulate at plant cell surfaceaccumulate at plant cell surface

SemitransparentSemitransparent

Restricts water lossRestricts water loss

Matrixes between Animal CellsMatrixes between Animal CellsAnimal cells have no cell wallsAnimal cells have no cell walls

Some are surrounded by a matrix Some are surrounded by a matrix

of cell secretions and other of cell secretions and other

materialmaterial

Prokaryotic StructureProkaryotic Structure

DNA

pilus

flagellum

cytoplasm with ribosomes

capsulecell wall

plasma membrane