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Unit 2: CellsUnit 2: Cells
Part II: Prokaryotes vs. EukaryotesPart II: Prokaryotes vs. Eukaryotes
Prokaryotes vs. Prokaryotes vs. EukaryotesEukaryotes
The differences between these The differences between these organisms go well beyond the presence organisms go well beyond the presence or lack of a nucleusor lack of a nucleus
This is the first major division of living This is the first major division of living things on earth – a very fundamental things on earth – a very fundamental difference indeeddifference indeed
We can no longer think of prokaryotes as We can no longer think of prokaryotes as primitive and eukaryotes advancedprimitive and eukaryotes advanced
Prokaryotes vs. Prokaryotes vs. EukaryotesEukaryotes
No nucleusNo nucleus ““Naked” DNA in a DNA Naked” DNA in a DNA
loop and plasmidsloop and plasmids Small ribosomes (70s; Small ribosomes (70s;
50s/30s subunits)50s/30s subunits) Cell walls made of Cell walls made of
peptidoglycanspeptidoglycans Flagella not made of Flagella not made of
microtubulesmicrotubules No EMS (endo-No EMS (endo-
membrane system)membrane system)
Double membrane bound Double membrane bound nucleusnucleus
DNA organized into DNA organized into chromosomeschromosomes
Large ribosomes (80s; Large ribosomes (80s; 60s/40s subunits)60s/40s subunits)
Cell walls made of Cell walls made of cellulose (plants) or chitin cellulose (plants) or chitin (fungi or protist)(fungi or protist)
Flagella made of Flagella made of microtubulesmicrotubules
EMS presentEMS present
Prokaryotes: DiversityProkaryotes: Diversity
The first forms of life were likely very similar The first forms of life were likely very similar to modern bacteriato modern bacteria
Rapidly evolving, but surprisingly nearly Rapidly evolving, but surprisingly nearly unchanged over billions of yearsunchanged over billions of years
Prokaryotes can be found in literally every Prokaryotes can be found in literally every environment and in every available niche on environment and in every available niche on the planetthe planet
Prokaryotes split into to major groups:Prokaryotes split into to major groups: Archaebacteria - extremophilesArchaebacteria - extremophiles Eubacteria – “true” bacteriaEubacteria – “true” bacteria
Prokaryotes: StructureProkaryotes: Structure
DNA Loop: a long single fiber in the cytoplasm DNA Loop: a long single fiber in the cytoplasm which contains almost all of the genetic material which contains almost all of the genetic material (the rest is in plasmids); genes are usually kept (the rest is in plasmids); genes are usually kept small and devoid of introns (extra non-coding bits small and devoid of introns (extra non-coding bits of DNA) – highly efficientof DNA) – highly efficient
Ribosomes: freely floating in cytoplasm Ribosomes: freely floating in cytoplasm (unbound); site for protein synthesis(unbound); site for protein synthesis Antibiotics like tetracycline bind to the prokaryotic Antibiotics like tetracycline bind to the prokaryotic
ribosome and interfere with the bacteria’s ability to ribosome and interfere with the bacteria’s ability to produce proteinsproduce proteins
Prokaryotes: StructureProkaryotes: Structure Cell Wall: provide the cell with shape and Cell Wall: provide the cell with shape and
structure, and some minimal protection against a structure, and some minimal protection against a hostile environment; most prokaryotes have themhostile environment; most prokaryotes have them
Capsule: jelly-like coating that surrounds the cell Capsule: jelly-like coating that surrounds the cell wall; only some prokaryotes have them; 4 wall; only some prokaryotes have them; 4 functions of a capsule:functions of a capsule: Prevents cell from drying outPrevents cell from drying out Helps cells stick together or on other surfaces (tissues Helps cells stick together or on other surfaces (tissues
of other organisms)of other organisms) Helps prokaryotes slide on surfacesHelps prokaryotes slide on surfaces Keeps some bacteria from being destroyed by the host Keeps some bacteria from being destroyed by the host
organismorganism
Prokaryotes: StructureProkaryotes: Structure Flagella: solid crystal proteins that stick Flagella: solid crystal proteins that stick
through the holes in the cell membrane and through the holes in the cell membrane and spin like propellers for locomotion (very spin like propellers for locomotion (very different structure from eukaryotic flagella)different structure from eukaryotic flagella)
Pilli: short bristle-like appendages which Pilli: short bristle-like appendages which have 2 functions:have 2 functions: Attach bacteria to surfacesAttach bacteria to surfaces Assist in the transfer of DNA from one Assist in the transfer of DNA from one
bacterium to anotherbacterium to another
Prokaryotes: ShapeProkaryotes: Shape
Eubacteria typically come in one of 4 Eubacteria typically come in one of 4 shapes:shapes: Coccus (pl. cocci): spere shapedCoccus (pl. cocci): spere shaped
Advantage: less distortion in a dried out organismAdvantage: less distortion in a dried out organism Bacillus (pl. bacilli): rod shapedBacillus (pl. bacilli): rod shaped
Advantage: high surface areaAdvantage: high surface area Spirillum (pl. spirilla): spiral/helical shapedSpirillum (pl. spirilla): spiral/helical shaped
Advantage: highly motile (corkscrew motion)Advantage: highly motile (corkscrew motion) Spirochete(s): spiral shaped cells with Spirochete(s): spiral shaped cells with
flagella inside the cell membraneflagella inside the cell membrane
Prokaryotes: MovementProkaryotes: Movement
Chemotaxis: movement of an organism Chemotaxis: movement of an organism toward or away from a chemicaltoward or away from a chemical Positive chemotaxis: chemicals that attract Positive chemotaxis: chemicals that attract
organisms toward them are called organisms toward them are called attractantsattractants
Negative chemotaxis: chemicals that repel Negative chemotaxis: chemicals that repel organisms are called repellantsorganisms are called repellants
Runs and twiddlesRuns and twiddles
Prokaryotes: SurvivalProkaryotes: Survival
When environmental conditions are When environmental conditions are unfavorable, bacteria become inactive.unfavorable, bacteria become inactive.
Some species form endospores (thick Some species form endospores (thick wall surrounding genetic materialwall surrounding genetic material
Endospores go dormant until conditions Endospores go dormant until conditions are favorableare favorable
Endospores can survive very harsh Endospores can survive very harsh environmental conditionsenvironmental conditions Boil water 2xBoil water 2x
Prokaryotes: Prokaryotes: ReproductionReproduction Asexual ReproductionAsexual Reproduction
Binary Fission: single loop of DNA is copied, Binary Fission: single loop of DNA is copied, both attach to cell membrane; the cell divides both attach to cell membrane; the cell divides by pinching off between the two loops.by pinching off between the two loops.
Sexual ReproductionSexual Reproduction Conjugation: a bridge is formed between cell Conjugation: a bridge is formed between cell
pili; F plasmid (F=fertility, ~ 25 genes) injected pili; F plasmid (F=fertility, ~ 25 genes) injected with F pilus; new plasmid is recombined into with F pilus; new plasmid is recombined into bacterial DNAbacterial DNA
ConjugationConjugation
Prokaryotes: Prokaryotes: ReproductionReproduction
Transformation: a living bacterium Transformation: a living bacterium absorbs the genetic material of a dead absorbs the genetic material of a dead cell or “naked” genetic material in the cell or “naked” genetic material in the environmentenvironment
Transduction: transfer of DNA from a Transduction: transfer of DNA from a host to another cell by means of a virushost to another cell by means of a virus
Prokaryotes: MetabolicsProkaryotes: Metabolics
Heterotrophs: must eat to acquire foodHeterotrophs: must eat to acquire food PhotoheterotrophsPhotoheterotrophs: can use light to produce : can use light to produce
ATP, but must get organic carbon from ATP, but must get organic carbon from another sourceanother source
ChemoheterotrophsChemoheterotrophs Saprobes: decomposers that absorb nutrients Saprobes: decomposers that absorb nutrients
from dead organic materialfrom dead organic material Parasites: absorb nutrients from the body fluids Parasites: absorb nutrients from the body fluids
of living hostsof living hosts Phagotrophs: ingest food and digest it Phagotrophs: ingest food and digest it
enzymatically within cells or multiple cellular enzymatically within cells or multiple cellular bodiesbodies
Prokaryotes: MetabolicsProkaryotes: Metabolics
Autotrophs: can produce their own foodAutotrophs: can produce their own food Photosynthetic autotrophsPhotosynthetic autotrophs (phototrophs): organisms (phototrophs): organisms
that harness light energy to drive the synthesis of that harness light energy to drive the synthesis of organic compounds from COorganic compounds from CO22
Chemosynthetic autotrophsChemosynthetic autotrophs (chemotrophs): (chemotrophs): organisms that use energy from specific inorganic organisms that use energy from specific inorganic substances to produce organic molecules from COsubstances to produce organic molecules from CO22
and provide life processesand provide life processes ChemoautotrophsChemoautotrophs: organisms that need only CO: organisms that need only CO22 as as
the carbon source; they obtain energy by oxidizing the carbon source; they obtain energy by oxidizing inorganic substances like hydrogen sulfide, inorganic substances like hydrogen sulfide, ammonia, ferrous or other ionsammonia, ferrous or other ions
Prokaryotes: OxygenProkaryotes: Oxygen
Prokaryotic oxygen requirements can be Prokaryotic oxygen requirements can be used to classify prokaryotes:used to classify prokaryotes: Obligate aerobesObligate aerobes: use oxygen for cellular : use oxygen for cellular
respiration and cannot survive without itrespiration and cannot survive without it Facultative anaerobesFacultative anaerobes: will use oxygen if : will use oxygen if
present, but can grow by fermentation in an present, but can grow by fermentation in an environment void of oxygenenvironment void of oxygen
Obligate anaerobesObligate anaerobes: cannot use oxygen and : cannot use oxygen and are killed by itare killed by it
Prokaryotes: Prokaryotes: ArchebacteriaArchebacteria
Archebacteria lack peptidoglycan in their Archebacteria lack peptidoglycan in their cell wallscell walls
Archebacteria have a unique lipid Archebacteria have a unique lipid composition in their cell membranescomposition in their cell membranes
Archebacteria have a different rRNA Archebacteria have a different rRNA structure than eubacteria and eukaryotesstructure than eubacteria and eukaryotes
Most Archebacteria live in extreme Most Archebacteria live in extreme environmentsenvironments
Prokaryotes: Prokaryotes: ArchebacteriaArchebacteria
Examples (subgroups):Examples (subgroups): Methanogens: use elemental hydrogen (H2) Methanogens: use elemental hydrogen (H2)
to reduce CO2 into methane (obligate to reduce CO2 into methane (obligate anaerobes)anaerobes)
Extreme Halophiles: live in high salinity Extreme Halophiles: live in high salinity environmentsenvironments
Thermoacidophiles: require environments Thermoacidophiles: require environments that are hot and acidicthat are hot and acidic
Eukaryotes: DiversityEukaryotes: Diversity
Protists: single celled, mostly Protists: single celled, mostly heterotrophic eukaryotic organismsheterotrophic eukaryotic organisms ie – amoeba, euglena, diatoms, etc…ie – amoeba, euglena, diatoms, etc…
Fungi: mostly multicellular, heterotrophic, Fungi: mostly multicellular, heterotrophic, sessile eukaryotic organismssessile eukaryotic organisms ie – mushrooms, molds, rusts (the living ie – mushrooms, molds, rusts (the living
kind)kind)
Eukaryotes: DiversityEukaryotes: Diversity
Plants: multicellular, autotrophic Plants: multicellular, autotrophic (photosynthetic), sessile eukaryotic (photosynthetic), sessile eukaryotic organismsorganisms ie – trees, grasses, bushes, shrubberiesie – trees, grasses, bushes, shrubberies
Animals: multicellular, heterotrophic, Animals: multicellular, heterotrophic, mostly motile eukaryotic organismsmostly motile eukaryotic organisms ie – sponges, mollusks, fish, insects, ie – sponges, mollusks, fish, insects,
reptiles, amphibians, birds, mammalsreptiles, amphibians, birds, mammals
Eukaryotes: StructureEukaryotes: Structure
NucleusNucleus Contains primary DNA in the Contains primary DNA in the
form of chromatin which can form of chromatin which can be packaged into be packaged into chromosomes for cellular chromosomes for cellular reproductionreproduction
Bound by a double membrane Bound by a double membrane (nuclear envelope) with (nuclear envelope) with nuclear pores for the nuclear pores for the exchange of RNAexchange of RNA
Eukaryotes: StructureEukaryotes: Structure
NucleolusNucleolus Dense, irregularly shaped body in the Dense, irregularly shaped body in the
nucleusnucleus Makes and stores RNAMakes and stores RNA Forms new ribosomesForms new ribosomes
Eukaryotes: StructureEukaryotes: Structure Mitochondrion (pl. mitochondria)Mitochondrion (pl. mitochondria)
Generate ATP (adenosine triphosphate – a Generate ATP (adenosine triphosphate – a high energy molecule for cellular energy)high energy molecule for cellular energy)
Double membrane; inner membrane = Double membrane; inner membrane = cristae, where much of cellular respiration cristae, where much of cellular respiration takes placetakes place
The area inside the cristae is The area inside the cristae is called the matrixcalled the matrixContain their own DNAContain their own DNA
Why?Why?
Eukaryotes: StructureEukaryotes: Structure
PlastidsPlastids Leucoplasts – found in Leucoplasts – found in
roots and tubersroots and tubers Chromoplasts – contain Chromoplasts – contain
accessory pigmentsaccessory pigments Chloroplasts – contain Chloroplasts – contain
chlorophyll pigments, chlorophyll pigments, found in leaves and stems found in leaves and stems and are the primary and are the primary photosynthetic organellephotosynthetic organelle
Eukaryotes: StructureEukaryotes: Structure
RibosomesRibosomes Non membrane-boundNon membrane-bound Site for protein synthesis (very numerous)Site for protein synthesis (very numerous) Translate mRNA code into proteinsTranslate mRNA code into proteins Made of RNA and proteinsMade of RNA and proteins 3 Types3 Types
70s - found in prokaryotes70s - found in prokaryotes 70s (o) – associated w/ eukaryotes’ ER70s (o) – associated w/ eukaryotes’ ER 80s – found in cytoplasm of eukaryotes80s – found in cytoplasm of eukaryotes
Eukaryotes: StructureEukaryotes: Structure Endoplasmic ReticulumEndoplasmic Reticulum
Provides internal framework, supportProvides internal framework, support Provides transportation and temporary storage Provides transportation and temporary storage
for organic compoundsfor organic compounds Provides surface area for the synthesis of Provides surface area for the synthesis of
organic compoundsorganic compounds Rough – contains ribosomes, site of protein and Rough – contains ribosomes, site of protein and
glycoprotein synthesis (usually for secretion)glycoprotein synthesis (usually for secretion) Smooth – no ribosomes, synthesize, secrete, and/or Smooth – no ribosomes, synthesize, secrete, and/or
store carbohydrates, steroids, hormones, lipids, or store carbohydrates, steroids, hormones, lipids, or other non-protein productsother non-protein products
Eukaryotes: StructureEukaryotes: Structure
Golgi (complex, apparatus, bodies)Golgi (complex, apparatus, bodies) Flattened membranous sacs stacked togetherFlattened membranous sacs stacked together
Sacs are called cisternaSacs are called cisterna Interiors are called the lumenInteriors are called the lumen
Cis face = forming face (input)Cis face = forming face (input) Trans face = maturing face (output)Trans face = maturing face (output) Functions: breaks down glycoproteins, Functions: breaks down glycoproteins,
concentrates materials into vesicles, forms the concentrates materials into vesicles, forms the cell wall, and produces lysosomescell wall, and produces lysosomes
Eukaryotes: StructureEukaryotes: Structure LysosomesLysosomes
Vesicle w/ highly reactive enzymes which can Vesicle w/ highly reactive enzymes which can break down proteins, nucleic acids, and lipidsbreak down proteins, nucleic acids, and lipids
Contain 2 or more hydrolases (enzymes)Contain 2 or more hydrolases (enzymes) ProteasesProteases NucleasesNucleases LipasesLipases
Acidic environment (pH 5) where enzymes Acidic environment (pH 5) where enzymes work bestwork best
““Suicide Bags” = programmed cell deathSuicide Bags” = programmed cell death
Eukaryotes: StructureEukaryotes: Structure
PeroxisomesPeroxisomes Contain oxidative enzymes which transfer H Contain oxidative enzymes which transfer H
from various substances to oxygenfrom various substances to oxygen Purines, fats, alcohol, poisons, hydrogen Purines, fats, alcohol, poisons, hydrogen
peroxide can all be broken down by peroxide can all be broken down by peroxisomesperoxisomes
Eukaryotes: StructureEukaryotes: Structure
VacuoleVacuole Membrane bound body with little or no Membrane bound body with little or no
internal structureinternal structure Vacuoles hold substances (varies from one Vacuoles hold substances (varies from one
cell to another)cell to another) Water, food, waste, pigments, enzymesWater, food, waste, pigments, enzymes
Formed by the pinching of the cell Formed by the pinching of the cell membranemembrane
Very large in plant cells (central vacuole), Very large in plant cells (central vacuole), smaller in animal cellssmaller in animal cells
Eukaryotes: StructureEukaryotes: Structure
CytoskeletonCytoskeleton Used to hold and change shapeUsed to hold and change shape Used for internal organizationUsed for internal organization Used for movement of molecules and/or Used for movement of molecules and/or
movement of the cellmovement of the cell Made of smaller organellesMade of smaller organelles
MicrotubulesMicrotubules Actin FibrilsActin Fibrils Intermediate FibrilsIntermediate Fibrils
Eukaryotes: StructureEukaryotes: Structure
Cell WallCell Wall Maintains cell shape, protection, prevents Maintains cell shape, protection, prevents
excessive uptake of waterexcessive uptake of water Made of polysaccharide cellulose embedded Made of polysaccharide cellulose embedded
in a matrix of other polysaccharides and in a matrix of other polysaccharides and proteinprotein
Walls of different cells glued together by Walls of different cells glued together by middle lamellamiddle lamella
Strengthens with age: secondary wallsStrengthens with age: secondary walls
Eukaryotes: StructureEukaryotes: Structure
Cell Membrane (or Plasma Membrane)Cell Membrane (or Plasma Membrane) Semi-permeable membrane surrounding all Semi-permeable membrane surrounding all
cellscells Made of phospholipids, proteins, cholesterol, Made of phospholipids, proteins, cholesterol,
carbohydrates, glycoproteins, and carbohydrates, glycoproteins, and glycolipidsglycolipids
Eukaryotes: StructureEukaryotes: Structure
Cell MembraneCell Membrane Fluid-Mosaic ModelFluid-Mosaic Model
Must be fluid to work properlyMust be fluid to work properly Cholesterol controls fluidity based on temperatureCholesterol controls fluidity based on temperature A mosaic of proteins is embedded and dispersed in A mosaic of proteins is embedded and dispersed in
the lipid bilayerthe lipid bilayer Integral proteins – inserted into the membraneIntegral proteins – inserted into the membrane Peripheral proteins – not embedded, attached to Peripheral proteins – not embedded, attached to
membrane surfacemembrane surface
Eukaryotes: FunctionEukaryotes: Function Movement of substances across the cell Movement of substances across the cell
membranemembrane Bulk FlowBulk Flow DiffusionDiffusion OsmosisOsmosis Facilitated DiffusionFacilitated Diffusion Active TransportActive Transport Vesicle Mediated TransportVesicle Mediated Transport Cell-Cell JunctionCell-Cell Junction
Eukaryotes: FunctionEukaryotes: Function
Bulk Flow Bulk Flow molecules move all together in the same molecules move all together in the same
direction due to force from hydrostatic direction due to force from hydrostatic pressurepressure
Diffusion (no energy)Diffusion (no energy) The movement of molecules from high The movement of molecules from high
concentration to low concentration with no concentration to low concentration with no energy requirement (small molecules only)energy requirement (small molecules only)
Eukaryotes: FunctionEukaryotes: Function
Osmosis (no energy)Osmosis (no energy) Special case of diffusion: movement of water Special case of diffusion: movement of water
across the membrane from high water across the membrane from high water potential to low water potentialpotential to low water potential
Facilitated Diffusion (no energy)Facilitated Diffusion (no energy) Polar molecules cannot get through by Polar molecules cannot get through by
diffusion, so cells use integral membrane diffusion, so cells use integral membrane proteins to transport them in/outproteins to transport them in/out
Transport proteins are highly selectiveTransport proteins are highly selective Uniport, symport, and antiport proteinsUniport, symport, and antiport proteins
Eukaryotes: FunctionEukaryotes: Function
Active Transport (energy)Active Transport (energy) When a substance is moved across the When a substance is moved across the
membrane membrane against it’s concentration against it’s concentration gradientgradient
Requires energy and membrane proteinsRequires energy and membrane proteins
Eukaryotes: FunctionEukaryotes: Function
Vesicle-Mediated TransportVesicle-Mediated Transport Vesicles/vacuoles can fuse with the cell Vesicles/vacuoles can fuse with the cell
membranemembrane Exocytosis: expulsion of contents outside Exocytosis: expulsion of contents outside
the cellthe cell Endocytosis: bringing in outside moleculesEndocytosis: bringing in outside molecules
Phagocytosis (cell eating)Phagocytosis (cell eating) Pinocytosis (cell drinking)Pinocytosis (cell drinking) Receptor-mediated endocytosisReceptor-mediated endocytosis
Eukaryotes: FunctionEukaryotes: Function
Cell-Cell JunctionCell-Cell Junction Cells organized into tissues must Cells organized into tissues must
communicate with each othercommunicate with each other Chemical signals (exocytosis from one, Chemical signals (exocytosis from one,
endocytosis into the next)endocytosis into the next) Other junctionsOther junctions
DesmosomeDesmosome Tight junctionTight junction Gap junctionGap junction plasmodesmaplasmodesma