Post on 23-Apr-2018
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Biology 102Biology 102
Lecture 5: CellsLecture 5: Cells
•• Fundamental unit of lifeFundamental unit of life
•• Smallest unit that displays all the basic Smallest unit that displays all the basic elements of lifeelements of life
The CellThe Cell
1.1. All living things are made of one or more cellsAll living things are made of one or more cells
Cell TheoryCell Theory
2. The simplest organisms are made of only one 2. The simplest organisms are made of only one cell; the cell is the functional unit of cell; the cell is the functional unit of
multicellularmulticellular organismsorganisms
Cell TheoryCell Theory
3.3. Each new cell arises from the division of Each new cell arises from the division of another, preanother, pre--existing cellexisting cell
Cell TheoryCell Theory
3. Each new cell arises from the division of 3. Each new cell arises from the division of another, preanother, pre--existing cellexisting cell
BacteriaBacteria
DrosophilaDrosophila
Cell TheoryCell Theory
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•• Two broad categoriesTwo broad categories
•• ProkaryotesProkaryotes
•• EukaryotesEukaryotes
Cell TypesCell Types
•• UnicellularUnicellular
•• All cells identical All cells identical –– no specialized functionno specialized function
•• Lack nucleus, other membraneLack nucleus, other membrane--bound organellesbound organelles
•• Example: bacteriaExample: bacteria
ProkaryotesProkaryotes
•• May be unicellularMay be unicellular
•• Examples: yeast, amoebasExamples: yeast, amoebas
EukaryotesEukaryotes
•• May be May be multicellularmulticellular
•• Examples: plants, animalsExamples: plants, animals
EukaryotesEukaryotes
•• Differ greatly in appearance and functionDiffer greatly in appearance and function
•• 4 basic components in common4 basic components in common
1.1. Plasma membranePlasma membrane
•• IsolationIsolation
•• ProtectionProtection
•• SensitivitySensitivity
•• SupportSupport
•• GatekeeperGatekeeper
Eukaryotic CellsEukaryotic Cells
•• Differ greatly in appearance and functionDiffer greatly in appearance and function
•• 4 basic components in common4 basic components in common
2. Cytoplasm2. Cytoplasm
•• Material inside theMaterial inside the
cell but outside thecell but outside the
nucleusnucleus
•• Contains the Contains the cytosolcytosol
and organellesand organelles
Eukaryotic CellsEukaryotic Cells
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•• Differ greatly in appearance and functionDiffer greatly in appearance and function
•• 4 basic components in common4 basic components in common
3. The nucleus3. The nucleus
•• Control center Control center –– thethe
“brain of the cell”“brain of the cell”
•• Contains the DNAContains the DNA
Eukaryotic CellsEukaryotic Cells
•• Differ greatly in appearance and functionDiffer greatly in appearance and function
•• 4 basic components in common4 basic components in common
4. Organelles4. Organelles
•• “Organs” of the cell“Organs” of the cell
•• Perform specificPerform specific
functionsfunctions
•• Some bound bySome bound by
membranesmembranes
Eukaryotic CellsEukaryotic Cells
•• Everything inside the membrane, except the Everything inside the membrane, except the nucleusnucleus
•• A LOT more on the membrane laterA LOT more on the membrane later
•• Includes…Includes…
•• CytosolCytosol = liquid portion= liquid portion
•• OrganellesOrganelles
CytoplasmCytoplasm
•• Cells are small, but molecules for their chemical Cells are small, but molecules for their chemical reactions are much smallerreactions are much smaller
Utah GeneticsUtah Genetics
Cell SizeCell Size
•• Glucose is 10Glucose is 1088 times smaller than a bacteriumtimes smaller than a bacterium
•• Reactants needed for metabolism are present in Reactants needed for metabolism are present in low concentrationslow concentrations
•• Low concentration means reactants don’t collide Low concentration means reactants don’t collide oftenoften
•• This makes chemical reactions slowThis makes chemical reactions slow
Cell SizeCell Size
•• Concentration gets lower as cells get biggerConcentration gets lower as cells get bigger
•• What happens to chemical reaction rate in cells What happens to chemical reaction rate in cells as cells get bigger?as cells get bigger?
Cell SizeCell Size
Cell Size
Relative Rate of Reaction
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•• Why prokaryotic cells stay smallWhy prokaryotic cells stay small
•• Eukaryotic cells have found a way around this: Eukaryotic cells have found a way around this: membranemembrane--bound organellesbound organelles
•• Serve to concentrate reactants in appropriate Serve to concentrate reactants in appropriate compartmentscompartments
•• Improves cell efficiencyImproves cell efficiency
Cell SizeCell Size
•• This means eukaryotic cells can be larger than This means eukaryotic cells can be larger than prokaryotic cellsprokaryotic cells
Cell SizeCell Size
•• Still, being small has some advantagesStill, being small has some advantages
•• Solutes taken into cells through membraneSolutes taken into cells through membrane
•• Consider 2 cubes (even though most cells are Consider 2 cubes (even though most cells are
spherical)…spherical)…
Cell SizeCell Size
2 µµµµm1 µµµµm
•• Complete the following calculations:Complete the following calculations:
Cell SizeCell Size
2 µµµµm1 µµµµm
Cell 1 Cell 2
Surface Area: length x width x 6
Volume: length x width x height
Surface Area/Volume
•• Which cell has the greater surface area?Which cell has the greater surface area?
•• Which cell has the greater volume?Which cell has the greater volume?
•• Which cell has the greater ratio of surface area Which cell has the greater ratio of surface area
to volume?to volume?
Cell SizeCell Size
•• Volume increases faster than surface area Volume increases faster than surface area
•• (x(x33 vsvs xx22))
•• So as cells get bigger, the proportion of surface So as cells get bigger, the proportion of surface
area decreasesarea decreases
•• Keeps cells smallKeeps cells small
•• Cells need surface area to absorb solutesCells need surface area to absorb solutes
•• Less surface area = fewer reactionsLess surface area = fewer reactions
Cell SizeCell Size
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OrganellesOrganelles
NonNon--membranousmembranous
•• Cell wallCell wall
•• CytoskeletonCytoskeleton
•• Cellular extensionsCellular extensions
•• MicrovilliMicrovilli
•• CiliaCilia
•• FlagellaFlagella
•• RibosomesRibosomes
MembranousMembranous
•• EndomembraneEndomembrane systemsystem
•• VacuolesVacuoles
Double MembraneDouble Membrane
•• NucleusNucleus
•• MitochondriaMitochondria
•• PlastidsPlastids
•• ChloroplastsChloroplasts
•• All cells are surrounded by a cell membraneAll cells are surrounded by a cell membrane
•• Also called a plasma membraneAlso called a plasma membrane
•• Consists of a Consists of a bilayerbilayer made of mostly made of mostly
phospholipidsphospholipids
•• Critical to cell functionCritical to cell function
•• Discussed in great detail laterDiscussed in great detail later
Cell MembraneCell Membrane
•• Plants, fungi, and bacteria are also have cell wallsPlants, fungi, and bacteria are also have cell walls
•• Animal cells do notAnimal cells do not
•• All have a cell membraneAll have a cell membrane
Cell WallCell Wall
Cell Cell
MembraneMembrane
•• Made of polysaccharides secreted through Made of polysaccharides secreted through plasma membraneplasma membrane
•• NonNon--livingliving
•• Exterior to cellExterior to cell
•• Cell walls of adjacent plant cells stuck together Cell walls of adjacent plant cells stuck together
with pectinwith pectin
Cell WallCell Wall
•• PorousPorous
•• Oxygen, carbon dioxide, water carrying small Oxygen, carbon dioxide, water carrying small molecules flow through freelymolecules flow through freely
Cell WallCell Wall
•• Adds strength and integrity to cellsAdds strength and integrity to cells
•• Plants, fungi don’t have bonesPlants, fungi don’t have bones
•• Allows them to withstand Allows them to withstand
gravity and wind and grow uprightgravity and wind and grow upright
Cell WallCell Wall
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•• Internal protein network of cellsInternal protein network of cells
•• Stabilize cell’s 3Stabilize cell’s 3--dimensional shapedimensional shape
•• Guide vesiclesGuide vesicles
CytoskeletonCytoskeleton
•• Formed from Formed from tubulintubulin subunitssubunits
1. Component of cytoskeleton 1. Component of cytoskeleton –– cell shape, cell shape, anchor organellesanchor organelles
MicrotubulesMicrotubules
2. Intracellular transport with motor proteins2. Intracellular transport with motor proteins
MicrotubulesMicrotubules
3. Move chromosomes during cell division3. Move chromosomes during cell division
MicrotubulesMicrotubules
4. Basis of cellular extensions4. Basis of cellular extensions
MicrotubulesMicrotubules Intermediate FilamentsIntermediate Filaments
•• >60 different kinds>60 different kinds
•• Resist stretchingResist stretching
•• Functions:Functions:
1. Strength1. Strength
2. Stabilize 2. Stabilize
organelle organelle
positionposition
3. Transport3. Transport
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MicrofilamentsMicrofilaments
•• Made of Made of actinactin subunitssubunits
•• Associated with cell movement, changes in cell Associated with cell movement, changes in cell shapeshape
Comparison of Comparison of CytoskeletalCytoskeletal ProteinsProteins
Cellular ExtensionsCellular Extensions
•• CiliaCilia
•• WhipWhip--likelike
•• Move substances in one direction across Move substances in one direction across
stationary cellsstationary cells
•• Example: tracheaExample: trachea
Cellular ExtensionsCellular Extensions
•• FlagellaFlagella
•• Substantially longer than ciliaSubstantially longer than cilia
•• Only example in human body: spermOnly example in human body: sperm
Cellular ExtensionsCellular Extensions
•• MicrovilliMicrovilli
•• Very small, highly numerousVery small, highly numerous
•• Increase absorptive surface areaIncrease absorptive surface area
•• Example: small intestineExample: small intestine
•• Site of protein synthesisSite of protein synthesis
•• Abundant in cells that produce a lot of proteinAbundant in cells that produce a lot of protein
•• Example: human liver cells have on average Example: human liver cells have on average
13 million 13 million ribosomesribosomes in each cell!in each cell!
RibosomesRibosomes
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•• Made from Made from rRNArRNA (2 units) and proteins(2 units) and proteins
•• Polypeptide chain constructed using information Polypeptide chain constructed using information provided by mRNAprovided by mRNA
RibosomesRibosomes
•• Many Many ribosomesribosomes can read the same strand of can read the same strand of mRNA at oncemRNA at once
RibosomesRibosomes
•• Contains information for…Contains information for…
•• Amino acid sequenceAmino acid sequence
•• Final destination of proteinFinal destination of protein
mRNAmRNA
•• Final destination of proteinFinal destination of protein
•• Bound for Bound for cytosolcytosol, = binds to free ribosome, = binds to free ribosome
mRNAmRNA
•• Final destination of protein somewhere else = Final destination of protein somewhere else = mRNA/ribosome complex associates with mRNA/ribosome complex associates with
endomembraneendomembrane systemsystem
mRNAmRNA
•• Elaborate system of membranes used to make Elaborate system of membranes used to make and move proteins in a celland move proteins in a cell
EndomembraneEndomembrane SystemSystem
OraganellesOraganelles UsedUsed
•• Rough ERRough ER
•• VesiclesVesicles
•• Golgi apparatusGolgi apparatus
•• Cell membraneCell membrane
•• LysosomeLysosome
Final Destination of ProteinFinal Destination of Protein
•• Outside cellOutside cell
•• Within cell membraneWithin cell membrane
•• LysosomeLysosome
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•• Collection of membranous tubes and envelopesCollection of membranous tubes and envelopes
•• 2 forms2 forms
•• Smooth endoplasmic reticulum (Smooth endoplasmic reticulum (sERsER))
•• Site of lipid synthesis, detoxificationSite of lipid synthesis, detoxification
•• Abundant in liver, kidney, endocrine glandsAbundant in liver, kidney, endocrine glands
Endoplasmic ReticulumEndoplasmic Reticulum
•• Rough endoplasmic reticulumRough endoplasmic reticulum
((rERrER) )
•• Gateway to Gateway to endomembraneendomembrane
systemsystem
•• Studded with ribosomesStudded with ribosomes
•• Proteins made by ribosomesProteins made by ribosomes
enter enter rERrER through porethrough pore
•• Portion of Portion of rERrER pinches off pinches off
to encapsulate protein in a to encapsulate protein in a
transport vesicletransport vesicle
Endoplasmic ReticulumEndoplasmic Reticulum
•• Some vesicles stay in cytoplasmSome vesicles stay in cytoplasm
•• Others migrate to the Golgi apparatusOthers migrate to the Golgi apparatus
EndomembraneEndomembrane SystemSystem Golgi ApparatusGolgi Apparatus
Transport vesicle
Vesicles bound for elsewhere
Cis face = Receiving face
Trans face = Shipping face
•• Proteins are modified and/or combined in the Proteins are modified and/or combined in the Golgi, encapsulated and transported to…Golgi, encapsulated and transported to…
1.1. Secretory vesiclesSecretory vesicles
•• Proteins for discharge from cellProteins for discharge from cell
•• Examples: insulin, antibodiesExamples: insulin, antibodies
Golgi ApparatusGolgi Apparatus
•• Proteins are modified and/or combined in the Proteins are modified and/or combined in the Golgi, encapsulated and transported to…Golgi, encapsulated and transported to…
2. Cell membrane components2. Cell membrane components
•• Example: Example: glycoproteinsglycoproteins
Golgi ApparatusGolgi Apparatus
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•• Proteins are modified and/or combined in the Proteins are modified and/or combined in the Golgi, encapsulated and transported to…Golgi, encapsulated and transported to…
3. 3. LysosomesLysosomes
•• CytosolicallyCytosolically--active vesiclesactive vesicles
Golgi ApparatusGolgi Apparatus
•• Contain more than 50 enzymesContain more than 50 enzymes
•• pH of ~4.5pH of ~4.5
•• Break down almost any Break down almost any biomoleculebiomolecule
•• Cell’s “garbage disposal”Cell’s “garbage disposal”
•• Can fuse with other membraneCan fuse with other membrane--defined defined structures and release contentsstructures and release contents
•• LysosomeLysosome storage diseases (>30)storage diseases (>30)
•• Example: Example: TayTay--Sachs diseaseSachs disease
LysosomesLysosomes
Rough
EndomembraneEndomembrane SystemSystem
•• Membranous, fluidMembranous, fluid--filled sacksfilled sacks
•• Most cells contain one or moreMost cells contain one or more
•• Animal cells have small onesAnimal cells have small ones
•• Plant cells typically have one large, central one Plant cells typically have one large, central one (may have other, small ones as well)(may have other, small ones as well)
VacuolesVacuoles
Animal Cell Plant Cell
•• Play a role in maintaining cell integrityPlay a role in maintaining cell integrity
•• Regulate cell’s water contentRegulate cell’s water content
•• Example: Paramecia have Example: Paramecia have contractile vacuoles contractile vacuoles
that expel water that leaks in through cell that expel water that leaks in through cell membranemembrane
VacuolesVacuoles
•• Example: Plant’s Example: Plant’s
central vacuole fills central vacuole fills
with water to with water to
generate generate
turgorturgor pressurepressure
VacuolesVacuoles
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•• Storage site in plantsStorage site in plants
•• Waste that can’t be excretedWaste that can’t be excreted
•• Poisonous compoundsPoisonous compounds
•• Makes some plants poisonous, taste badMakes some plants poisonous, taste bad
•• Amino acids, sugarsAmino acids, sugars
•• Pigment (flowers)Pigment (flowers)
VacuolesVacuoles NucleusNucleus
•• Control center of cellControl center of cell
•• Surrounded by nuclear envelopeSurrounded by nuclear envelope
•• Double membraneDouble membrane
•• Covered with poresCovered with pores
•• Water, ions pass Water, ions pass
through freelythrough freely
•• Ribosomes stud outerRibosomes stud outer
membranemembrane
•• Continuous withContinuous with
endomembraneendomembrane systemsystem
NucleusNucleus
•• Contains chromatinContains chromatin
•• DNA and associatedDNA and associated
proteinsproteins
•• Contains allContains all
instructions forinstructions for
building cell’s proteinsbuilding cell’s proteins
•• Dictates types, Dictates types,
amounts of proteins amounts of proteins
to be madeto be made
NucleusNucleus
•• mRNA made in nucleusmRNA made in nucleus
•• Exits through nuclearExits through nuclear
porespores
•• Finds ribosomesFinds ribosomes
•• Translated into proteinTranslated into protein
in the cytoplasmin the cytoplasm
NucleusNucleus
•• Contains nucleolusContains nucleolus
•• Site of ribosome Site of ribosome
synthesissynthesis
•• Site of ATP synthesis Site of ATP synthesis –– “powerhouse of cell”“powerhouse of cell”
•• Double membrane (inner and outer)Double membrane (inner and outer)
•• Outer membrane is smoothOuter membrane is smooth
•• Inner membrane has deep folds called Inner membrane has deep folds called cristaecristae
MitochondriaMitochondria
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•• Carry own DNACarry own DNA
•• Make some of their own protein (contain Make some of their own protein (contain ribosomes)ribosomes)
•• Only cellular site to use molecular oxygenOnly cellular site to use molecular oxygen
MitochondriaMitochondria
•• Provide energy = most abundant in cells that Provide energy = most abundant in cells that need a lot of energyneed a lot of energy
•• Compare: sperm Compare: sperm vsvs cartilagecartilage
MitochondriaMitochondria
•• Contained ONLY photosynthetic organismsContained ONLY photosynthetic organisms
•• Primarily used for storagePrimarily used for storage
•• Pigments (fruit)Pigments (fruit)
•• StarchStarch
PlastidsPlastids
•• Highly specialized plastidHighly specialized plastid
•• Site of photosynthesisSite of photosynthesis
•• ContainsContains
•• StromaStroma (fluid)(fluid)
•• ThylakoidsThylakoids (membranous sacks)(membranous sacks)
ChloroplastsChloroplasts
•• ThylakoidsThylakoids contain a pigment called contain a pigment called chlorophyllchlorophyll
•• Gives plants green colorGives plants green color
•• Captures energy from sunlightCaptures energy from sunlight
•• Transfers energy to other moleculesTransfers energy to other molecules
•• Energy used to drive photosynthesisEnergy used to drive photosynthesis
•• Sugar is made from COSugar is made from CO22 and Hand H22OO
ChloroplastsChloroplasts