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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