unit 2: cells

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


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?


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


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


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


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


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


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


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


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


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)


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


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


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


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

unit 2: cells

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