Cell Structure and Cell Structure and FunctionFunction
Chapter OutlineChapter Outline
Cell theoryCell theory Properties common to all cellsProperties common to all cells Cell size and shape – Cell size and shape – why are cells so small?why are cells so small? Prokaryotic cellsProkaryotic cells Eukaryotic cellsEukaryotic cells
Organelles and structure in all eukaryotic cellOrganelles and structure in all eukaryotic cell Organelles in plant cells but not animalOrganelles in plant cells but not animal
Cell junctionsCell junctions
History of Cell TheoryHistory of Cell Theory
mid 1600s – Anton van Leeuwenhoekmid 1600s – Anton van Leeuwenhoek Improved microscope, observed many living cellsImproved microscope, observed many living cells
mid 1600s – Robert Hooke mid 1600s – Robert Hooke Observed many cells including cork cellsObserved many cells including cork cells
1850 – Rudolf Virchow1850 – Rudolf Virchow Proposed that all cells come from existing Proposed that all cells come from existing
cellscells
Cell TheoryCell Theory
1.1. All organisms consist of 1 or more All organisms consist of 1 or more cells.cells.
2.2. Cell is the smallest unit of life.Cell is the smallest unit of life.
3.3. All cells come from pre-existing All cells come from pre-existing cells.cells.
Observing Cells Observing Cells (4.1)(4.1)
Light microscopeLight microscope Can observe living cells in true colorCan observe living cells in true color Magnification of up to ~1000xMagnification of up to ~1000x Resolution ~ 0.2 microns – 0.5 micronsResolution ~ 0.2 microns – 0.5 microns
Observing Cells Observing Cells (4.1)(4.1)
Electron MicroscopesElectron Microscopes Preparation needed kills the cellsPreparation needed kills the cells Images are black and white – may be Images are black and white – may be
colorizedcolorized Magnifcation up to ~100,000Magnifcation up to ~100,000
• Transmission electron microscope (TEM)Transmission electron microscope (TEM) 2-D image2-D image
• Scanning electron microscope (SEM)Scanning electron microscope (SEM) 3-D image3-D image
SEM
TEM
Cell StructureCell Structure
All Cells have:All Cells have: an outermost plasma membranean outermost plasma membrane genetic material in the form of DNA genetic material in the form of DNA cytoplasm with ribosomescytoplasm with ribosomes
Cell StructureCell Structure
All Cells have:All Cells have: an outermost plasma membranean outermost plasma membrane
• Structure – phospholipid bilayer with Structure – phospholipid bilayer with embedded proteinsembedded proteins
• Function – isolates cell contents, Function – isolates cell contents, controls what gets in and out of the controls what gets in and out of the cell, receives signalscell, receives signals
Cell StructureCell Structure
All Cells have:All Cells have: genetic material in the form of DNAgenetic material in the form of DNA
• Eukaryotes – DNA is within a Eukaryotes – DNA is within a membrane (nucleus)membrane (nucleus)
• Prokaryotes – no membrane around Prokaryotes – no membrane around the DNA (DNA region called nucleoid)the DNA (DNA region called nucleoid)
Cell StructureCell Structure
All Cells have:All Cells have: cytoplasm with ribosomescytoplasm with ribosomes
• Cytoplasm – fluid area inside outer Cytoplasm – fluid area inside outer plasma membrane and outside DNA plasma membrane and outside DNA regionregion
• Ribosome – site of protein synthesisRibosome – site of protein synthesis
Why Are Cells So Small? Why Are Cells So Small? (4.2)(4.2)
Cells need sufficient surface area to allow Cells need sufficient surface area to allow adequate transport of nutrients in and adequate transport of nutrients in and wastes out.wastes out.
As cell volume increases, so does the As cell volume increases, so does the need for the transporting of nutrients and need for the transporting of nutrients and wastes.wastes.
Why Are Cells So Small?Why Are Cells So Small?
However, as cell volume increases the However, as cell volume increases the surface area of the cell does not expand surface area of the cell does not expand as quickly.as quickly. If the cell’s volume gets too large it cannot If the cell’s volume gets too large it cannot
transport enough wastes out or nutrients in. transport enough wastes out or nutrients in. Thus, surface area limits cell volume/size.Thus, surface area limits cell volume/size.
Why Are Cells So Small?Why Are Cells So Small?
Strategies for increasing surface Strategies for increasing surface area, so cell can be larger:area, so cell can be larger: ““Frilly” edged…….Frilly” edged……. Long and narrow…..Long and narrow…..
Round cells will always be small.Round cells will always be small.
Prokaryotic Cell StructureProkaryotic Cell Structure
Prokaryotic Cells are smaller and Prokaryotic Cells are smaller and simpler in structure than eukaryotic simpler in structure than eukaryotic cells.cells. Typical prokaryotic cell is __________Typical prokaryotic cell is __________ Prokaryotic cells do NOT have:Prokaryotic cells do NOT have:
• NucleusNucleus• Membrane bound organellesMembrane bound organelles
Prokaryotic Cell StructureProkaryotic Cell Structure
StructuresStructures Plasma membrane Plasma membrane Cell wallCell wall Cytoplasm with ribosomesCytoplasm with ribosomes NucleoidNucleoid Capsule*Capsule* Flagella* and pili*Flagella* and pili*
*present in some, but not all prokaryotic cells*present in some, but not all prokaryotic cells
Prokaryotic CellProkaryotic Cell
TEM Prokaryotic Cell
Eukaryotic CellsEukaryotic Cells
Structures in all eukaryotic cellsStructures in all eukaryotic cells NucleusNucleus RibosomesRibosomes Endomembrane System Endomembrane System
• Endoplasmic reticulum – smooth and roughEndoplasmic reticulum – smooth and rough• Golgi apparatusGolgi apparatus• VesiclesVesicles
MitochondriaMitochondria CytoskeletonCytoskeleton
CYTOSKELETON
MITOCHONDRION
CENTRIOLES
LYSOSOME
GOLGI BODY
SMOOTH ER
ROUGH ER
RIBOSOMES
NUCLEUS
PLASMA MEMBRANE
Fig. 4-15b, p.59
Nucleus Nucleus (4.5)(4.5)
FunctionFunction – isolates the cell’s genetic – isolates the cell’s genetic material, DNAmaterial, DNA DNA directs/controls the activities of the cellDNA directs/controls the activities of the cell
• DNA determines which types of RNA are madeDNA determines which types of RNA are made• The RNA leaves the nucleus and directs the The RNA leaves the nucleus and directs the
synthesis of proteins in the cytoplasmsynthesis of proteins in the cytoplasm
NucleusNucleus
StructureStructure Nuclear envelopeNuclear envelope
• Two Phospholipid bilayers with protein Two Phospholipid bilayers with protein lined poreslined pores
Each pore is a ring of 8 proteins with an Each pore is a ring of 8 proteins with an opening in the center of the ringopening in the center of the ring
Nucleoplasm – fluid of the nucleusNucleoplasm – fluid of the nucleus
Nuclear pore bilayer facing cytoplasm Nuclear envelope
bilayer facing nucleoplasm
Fig. 4-17, p.61
NucleusNucleus
DNA is arranged in chromosomesDNA is arranged in chromosomes Chromosome – fiber of DNA and the Chromosome – fiber of DNA and the
proteins attached to the DNAproteins attached to the DNA
Chromatin – all of the cell’s DNA and Chromatin – all of the cell’s DNA and the associated proteinsthe associated proteins
NucleusNucleus
Structure, Structure, continuedcontinued
NucleolusNucleolus• Area of condensed DNAArea of condensed DNA• Where ribosomal subunits are madeWhere ribosomal subunits are made
Subunits exit the nucleus via nuclear poresSubunits exit the nucleus via nuclear pores
Endomembrane System Endomembrane System (4.6 – 4.9)(4.6 – 4.9)
Series of organelles responsible for:Series of organelles responsible for: Modifying protein chains into their final Modifying protein chains into their final
formform Synthesizing of lipidsSynthesizing of lipids Packaging of fully modified proteins and Packaging of fully modified proteins and
lipids into vesicles for export or use in lipids into vesicles for export or use in the cellthe cell
Endomembrane SystemEndomembrane System
Endoplasmic Reticulum (ER)Endoplasmic Reticulum (ER) Continuous with the outer membrane of Continuous with the outer membrane of
the nuclear envelope the nuclear envelope Two forms - smooth and roughTwo forms - smooth and rough
Transport vesiclesTransport vesicles Golgi apparatusGolgi apparatus
Endoplasmic ReticulumEndoplasmic Reticulum
Rough Endoplasmic Reticulum (RER)Rough Endoplasmic Reticulum (RER)• Network of flattened membrane sacs create Network of flattened membrane sacs create
a “maze”a “maze”• Ribosomes attached to the outside of the Ribosomes attached to the outside of the
RER make it appear roughRER make it appear rough
Endoplasmic ReticulumEndoplasmic Reticulum
Function RERFunction RER• Where proteins are modified and packaged Where proteins are modified and packaged
in transport vesicles for transport to the in transport vesicles for transport to the Golgi bodyGolgi body
Endomembrane SystemEndomembrane System
Smooth ER (SER)Smooth ER (SER) Tubular membrane structureTubular membrane structure Continuous with RERContinuous with RER No ribosomes attachedNo ribosomes attached
Function SERFunction SER Synthesis of lipids (fatty acids, phospholipids, Synthesis of lipids (fatty acids, phospholipids,
sterols..)sterols..)
Endomembrane SystemEndomembrane System
Additional functions of the SERAdditional functions of the SER In muscle cells, the SER stores calcium ions In muscle cells, the SER stores calcium ions
and releases them during muscle contractionsand releases them during muscle contractions In liver cells, the SER detoxifies medications In liver cells, the SER detoxifies medications
and alcoholand alcohol
Golgi ApparatusGolgi Apparatus
Golgi Apparatus Golgi Apparatus Stack of flattened membrane sacsStack of flattened membrane sacs
Function Golgi apparatusFunction Golgi apparatus Completes the processing substances Completes the processing substances
received from the ERreceived from the ER Sorts, tags and packages fully processed Sorts, tags and packages fully processed
proteins and lipids in vesiclesproteins and lipids in vesicles
Golgi ApparatusGolgi Apparatus
Golgi apparatus receives transport Golgi apparatus receives transport vesicles from the ER on one side of the vesicles from the ER on one side of the organelleorganelle Vesicle binds to the first layer of the Golgi and Vesicle binds to the first layer of the Golgi and
its contents enter the Golgiits contents enter the Golgi
Golgi ApparatusGolgi Apparatus
The proteins and lipids are modified as they The proteins and lipids are modified as they pass through layers of the Golgipass through layers of the Golgi
Molecular tags are added to the fully modified Molecular tags are added to the fully modified substancessubstances• These tags allow the substances to be sorted and These tags allow the substances to be sorted and
packaged appropriately.packaged appropriately.• Tags also indicate where the substance is to be Tags also indicate where the substance is to be
shipped.shipped.
Golgi ApparatusGolgi Apparatus
Transport VesiclesTransport Vesicles
Transport VesiclesTransport Vesicles Vesicle = small membrane bound sacVesicle = small membrane bound sac Transport modified proteins and lipids from Transport modified proteins and lipids from
the ER to the Golgi apparatus (and from Golgi the ER to the Golgi apparatus (and from Golgi to final destination)to final destination)
Endomembrane SystemEndomembrane System
Putting it all togetherPutting it all together DNA directs RNA synthesis DNA directs RNA synthesis RNA RNA
exits nucleus through a nuclear pore exits nucleus through a nuclear pore ribosome ribosome protein is made protein is made proteins proteins with proper code enter RER with proper code enter RER proteins proteins are modified in RER and lipids are made are modified in RER and lipids are made in SER in SER vesicles containing the vesicles containing the proteins and lipids bud off from the ERproteins and lipids bud off from the ER
Endomembrane SystemEndomembrane System
Putting it all togetherPutting it all together
ER vesicles merge with Golgi body ER vesicles merge with Golgi body proteins and lipids enter Golgi proteins and lipids enter Golgi each is each is fully modified as it passes through fully modified as it passes through layers of Golgi layers of Golgi modified products are modified products are tagged, sorted and bud off in Golgi tagged, sorted and bud off in Golgi vesicles vesicles … …
Endomembrane SystemEndomembrane System
Putting it all togetherPutting it all together
Golgi vesicles either merge with the Golgi vesicles either merge with the plasma membrane and release their plasma membrane and release their contents OR remain in the cell and contents OR remain in the cell and serve a purposeserve a purpose
VesiclesVesicles
Vesicles - small membrane bound sacsVesicles - small membrane bound sacs ExamplesExamples
• Golgi and ER transport vesiclesGolgi and ER transport vesicles• Peroxisome Peroxisome
Where fatty acids are metabolizedWhere fatty acids are metabolized Where hydrogen peroxide is detoxifiedWhere hydrogen peroxide is detoxified
• LysosomeLysosome
Lysosomes Lysosomes (4.10)(4.10)
The lysosome is an example of an The lysosome is an example of an organelle made at the Golgi apparatus.organelle made at the Golgi apparatus. Golgi packages digestive enzymes in a Golgi packages digestive enzymes in a
vesicle. The vesicle remains in the cell and:vesicle. The vesicle remains in the cell and:• Digests unwanted or damaged cell partsDigests unwanted or damaged cell parts• Merges with food vacuoles and digest the contentsMerges with food vacuoles and digest the contents
• Figure 4.10AFigure 4.10A
Lysosomes Lysosomes (4.11)(4.11)
Tay-Sachs disease occurs when the Tay-Sachs disease occurs when the lysosome is missing the enzyme needed lysosome is missing the enzyme needed to digest a lipid found in nerve cells.to digest a lipid found in nerve cells. As a result the lipid accumulates and nerve As a result the lipid accumulates and nerve
cells are damaged as the lysosome swells cells are damaged as the lysosome swells with undigested lipid.with undigested lipid.
Mitochondria Mitochondria (4.15)(4.15)
Function – synthesis of ATPFunction – synthesis of ATP 3 major pathways involved in ATP 3 major pathways involved in ATP
productionproduction1.1. GlycolysisGlycolysis
2.2. Krebs CycleKrebs Cycle
3.3. Electron transport system (ETS)Electron transport system (ETS)
MitochondriaMitochondria
Structure: Structure: ~1-5 microns~1-5 microns Outer membraneOuter membrane Inner membrane - Highly foldedInner membrane - Highly folded
• Folds called cristaeFolds called cristae Intermembrane space (or outer compartment)Intermembrane space (or outer compartment) Matrix Matrix
• DNA and ribosomes in matrixDNA and ribosomes in matrix
MitochondriaMitochondria
Mitochondria Mitochondria (4.15)(4.15)
Function – synthesis of ATPFunction – synthesis of ATP 3 major pathways involved in ATP 3 major pathways involved in ATP
productionproduction1.1. Glycolysis - cytoplasmGlycolysis - cytoplasm
2.2. Krebs Cycle - matrixKrebs Cycle - matrix
3.3. Electron transport system (ETS) - Electron transport system (ETS) - intermembrane spaceintermembrane space
MitochondriaMitochondria
TEMTEM
Vacuoles Vacuoles (4.12)(4.12)
Vacuoles are membrane sacs that are Vacuoles are membrane sacs that are generally larger than vesicles.generally larger than vesicles. Examples:Examples:
• Food vacuole - formed when protists bring food Food vacuole - formed when protists bring food into the cell by endocytosisinto the cell by endocytosis
• Contractile vacuole – collect and pump excess Contractile vacuole – collect and pump excess
water out of some freshwater protistswater out of some freshwater protists
• Central vacuole – covered laterCentral vacuole – covered later
Cytoskeleton Cytoskeleton (4.16, 4.17)(4.16, 4.17)
FunctionFunction gives cells internal organization, shape, and gives cells internal organization, shape, and
ability to moveability to move StructureStructure
Interconnected system of microtubules, Interconnected system of microtubules, microfilaments, and intermediate filaments microfilaments, and intermediate filaments (animal only)(animal only)• All are proteinsAll are proteins
CytoskeletonCytoskeleton
MicrofilamentsMicrofilaments
Thinnest cytoskeletal elements (rodlike)Thinnest cytoskeletal elements (rodlike)
Composed of the globular protein Composed of the globular protein actin actin
Enable cells to change shape and moveEnable cells to change shape and move
CytoskeletonCytoskeleton
Intermediate filamentsIntermediate filaments Present only in animal cells of Present only in animal cells of
certain tissuescertain tissues
Fibrous proteins join to form a Fibrous proteins join to form a rope-like structurerope-like structure• Provide internal structureProvide internal structure• Anchor organelles in place.Anchor organelles in place.
CytoskeletonCytoskeleton
Microtubules – long hollow Microtubules – long hollow tubes made of tubulin proteins tubes made of tubulin proteins (globular)(globular) Anchor organelles and act as Anchor organelles and act as
tracks for organelle movementtracks for organelle movement Move chromosomes around Move chromosomes around
during cell divisionduring cell division• Used to make cilia and flagellaUsed to make cilia and flagella
Cilia Cilia and and flagellaflagella (structures for cell motility) (structures for cell motility)
Move whole cells or materials across the cell surface Move whole cells or materials across the cell surface
Microtubules wrapped in an extension of the plasma Microtubules wrapped in an extension of the plasma membrane (9 + 2 arrangement of MT)membrane (9 + 2 arrangement of MT)
Plant Cell StructuresPlant Cell Structures
Structures found in plant, but not animal Structures found in plant, but not animal cellscells ChloroplastsChloroplasts Central vacuoleCentral vacuole Other plastids/vacuoles – chromoplast, Other plastids/vacuoles – chromoplast,
amyloplastamyloplast Cell wallCell wall
Chloroplasts Chloroplasts (4.14)(4.14)
Function – site of photosynthesisFunction – site of photosynthesis StructureStructure
2 outer membranes2 outer membranes Thylakoid membrane systemThylakoid membrane system
• Stacked membrane sacs called granumStacked membrane sacs called granum Chlorophyll in granumChlorophyll in granum StromaStroma
• Fluid part of chloroplastFluid part of chloroplast
Plastids/Vacuoles in PlantsPlastids/Vacuoles in Plants
Chromoplasts – contain colored pigmentsChromoplasts – contain colored pigments• Pigments called carotenoidsPigments called carotenoids
Amyloplasts – store starchAmyloplasts – store starch
Central VacuoleCentral Vacuole
Function – storage area for water, sugars, Function – storage area for water, sugars, ions, amino acids, and wastesions, amino acids, and wastes Some central vacuoles serve specialized Some central vacuoles serve specialized
functions in plant cells.functions in plant cells.• May contain poisons to protect against predatorsMay contain poisons to protect against predators
Central VacuoleCentral Vacuole
StructureStructure Large membrane bound sacLarge membrane bound sac Occupies the majority of the volume of the Occupies the majority of the volume of the
plant cellplant cell Increases cell’s surface area for transport of Increases cell’s surface area for transport of
substances substances cells can be larger cells can be larger
Cell surfaces protect, support, and join cellsCell surfaces protect, support, and join cells
Cells interact with their environments and Cells interact with their environments and each other via their surfaceseach other via their surfaces
Many cells are protected by more than the Many cells are protected by more than the plasma membraneplasma membrane
Cell WallCell Wall
Function – provides structure and protectionFunction – provides structure and protection Never found in animal cellsNever found in animal cells Present in plant, bacterial, fungus, and some protistsPresent in plant, bacterial, fungus, and some protists
StructureStructure Wraps around the plasma membraneWraps around the plasma membrane Made of cellulose and other polysaccharidesMade of cellulose and other polysaccharides Connect by plasmodesmata Connect by plasmodesmata (channels through the walls)(channels through the walls)
Vacuole
Wallsof twoadjacentplant cells
Plasmodesmata
Layersof one plantcell wall
Cytoplasm
Plasma membrane
Plant Cell TEMPlant Cell TEM
Typical Plant CellTypical Plant Cell
Typical Plant CellTypical Plant Cell
Origin of Mitochondria and Origin of Mitochondria and ChloroplastsChloroplasts
Both organelles are believed to have once Both organelles are believed to have once been free-living bacteria that were been free-living bacteria that were engulfed by a larger cell.engulfed by a larger cell.
Proposed Origin of Mitochondria Proposed Origin of Mitochondria and Chloroplasts and Chloroplasts
Evidence:Evidence: Each have their own DNAEach have their own DNA Their ribosomes resemble bacterial ribosomesTheir ribosomes resemble bacterial ribosomes Each can divide on its ownEach can divide on its own Mitochondria are same size as bacteriaMitochondria are same size as bacteria Each have more than one membraneEach have more than one membrane
Cell Junctions Cell Junctions (4.18)(4.18)
Plasma membrane proteins connect Plasma membrane proteins connect neighboring cells - called cell junctionsneighboring cells - called cell junctions
Plant cells – plasmodesmata provide Plant cells – plasmodesmata provide channels between cellschannels between cells
Cell Junctions Cell Junctions (4.18)(4.18)
3 types of cell junctions in animal cells3 types of cell junctions in animal cells1.1. Tight junctionsTight junctions
2.2. Adchoring junctionsAdchoring junctions
3.3. Gap junctionsGap junctions
Cell JunctionsCell Junctions
1.1. Tight junctions – membrane proteins seal Tight junctions – membrane proteins seal neighboring cells so that water soluble neighboring cells so that water soluble substances cannot cross between themsubstances cannot cross between them
• See between stomach cellsSee between stomach cells
Cell JunctionsCell Junctions
2.2. Anchoring junctions – cytoskeleton fibers Anchoring junctions – cytoskeleton fibers join cells in tissues that need to stretchjoin cells in tissues that need to stretch
• See between heart, skin, and muscle cellsSee between heart, skin, and muscle cells
3.3. Gap junctions – membrane proteins on Gap junctions – membrane proteins on neighboring cells link to form channelsneighboring cells link to form channels
• This links the cytoplasm of adjoining cellsThis links the cytoplasm of adjoining cells
Gap junction
Anchoring junction
Tight junction