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Chapter 4Chapter 4

The Cell: The Cell:

The Fundamental Unit of LifeThe Fundamental Unit of Life

Lecture 3: OrganellesLecture 3: Organelles

•• We previously talked about the cell membraneWe previously talked about the cell membrane

•• The The cytoplasmcytoplasm is everything inside the is everything inside the

membrane, except the nucleusmembrane, except the nucleus

•• Includes…Includes…

•• CytosolCytosol = liquid portion= liquid portion

•• Organelles (NOTE ERROR IN STUDY GUIDE)Organelles (NOTE ERROR IN STUDY GUIDE)

Cell MakeupCell Makeup

•• 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 Glucose is 101088 times smallertimes smaller than a bacteriumthan a bacterium

•• Reactants needed for metabolism are present in Reactants needed for metabolism are present in

lowlow concentrationsconcentrations

•• Low concentration means reactants don’t collide Low concentration means reactants don’t collide

oftenoften

(Don’t draw this(Don’t draw this

in your study guide)in your study guide)

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?

(Draw this one(Draw this one

in your study guide)in your study guide)

Cell SizeCell Size

Cell Size

Rel

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e Rat

e of

Rea

ctio

n

•• 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

•• Improve cell efficiencyImprove cell efficiency

Cell SizeCell Size

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•• 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 Still, being small has some advantagesadvantages

•• 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

•• 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

•• Often categorized by presence/absence of Often categorized by presence/absence of

membrane(s)membrane(s)

OrganellesOrganelles

•• NonNon--membranousmembranous

•• CytoskeletonCytoskeleton

•• Cellular extensionsCellular extensions

•• MicrovilliMicrovilli

•• CiliaCilia

•• FlagellaFlagella

•• RibosomesRibosomes

•• MembranousMembranous

•• MitochondriaMitochondria

•• Endoplasmic Endoplasmic

reticulumreticulum

•• Golgi Golgi aparatusaparatus

•• LysosomesLysosomes

•• PeroxisomesPeroxisomes

•• NucleusNucleus

•• We will consider the organelles’ contribution to We will consider the organelles’ contribution to

the production and management of proteinthe production and management of protein

OrganellesOrganelles

•• NonNon--membranousmembranous

•• CytoskeletonCytoskeleton

•• Cellular extensionsCellular extensions

•• MicrovilliMicrovilli

•• CiliaCilia

•• FlagellaFlagella

•• RibosomesRibosomes

•• MembranousMembranous

•• MitochondriaMitochondria

•• Endoplasmic Endoplasmic reticulumreticulum

•• Golgi Golgi aparatusaparatus

•• LysosomesLysosomes

•• PeroxisomesPeroxisomes

•• NucleusNucleus

•• 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)(2 units)

•• Polypeptide chain constructed using information Polypeptide chain constructed using information

provided by provided by mRNAmRNA

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 proteinFinal destination of protein

•• Bound for export, membrane, or membraneBound for export, membrane, or membrane--

bound organelle = mRNA/ribosome complex bound organelle = mRNA/ribosome complex

associates with associates with endoplasmic reticulumendoplasmic reticulum

mRNAmRNA

•• 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

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•• Proteins enter Proteins enter rERrER

through porethrough pore

•• Portion of Portion of rERrER pinches pinches

off to encapsulate off to encapsulate

protein in a transport protein in a transport

vesiclevesicle

Rough Endoplasmic ReticulumRough Endoplasmic Reticulum

•• Some vesicles stay in cytoplasmSome vesicles stay in cytoplasm

•• Others migrate to the Golgi apparatusOthers migrate to the Golgi apparatus

Rough Endoplasmic ReticulumRough Endoplasmic Reticulum

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

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. 2. Cell membrane componentsCell membrane components

•• Example: Example: glycoproteinsglycoproteins

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…

3. 3. LysosomesLysosomes

•• CytosolicallyCytosolically--active vesiclesactive vesicles

Golgi ApparatusGolgi Apparatus

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•• 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

•• Originate in Originate in rERrER

•• Involved in lipid catabolism, modificationInvolved in lipid catabolism, modification

•• Produce oxidative enzymes, hydrogen peroxideProduce oxidative enzymes, hydrogen peroxide

•• Detoxifies substances in kidney by means of Detoxifies substances in kidney by means of

peroxidationperoxidation

PeroxisomesPeroxisomes

•• Site of ATP synthesis Site of ATP synthesis –– “powerhouse of cell”“powerhouse of cell”

•• Features:Features:

•• Double membrane (inner and outer)Double membrane (inner and outer)

•• Carry own DNA, make some of their own Carry own DNA, make some of their own

proteinprotein

•• 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

•• Examples: muscle cells, spermExamples: muscle cells, sperm

MitochondriaMitochondria

•• Internal protein network of cellsInternal protein network of cells

•• Stabilize cell’s 3Stabilize cell’s 3--dimensional shapedimensional shape

•• Guide vesiclesGuide vesicles

CytoskeletonCytoskeleton

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•• 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. Cilia, flagella4. Cilia, flagella

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

MicrofilamentsMicrofilaments

•• Made of Made of actinactin subunitssubunits

•• Associated with cell movement, changes in cell Associated with cell movement, changes in cell

shapeshape

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Comparison of Comparison of CytoskeletalCytoskeletal ProteinsProteins Thick FilamentsThick Filaments

•• ~15nm diameter~15nm diameter

•• Microfilaments = 3Microfilaments = 3--6nm in diameter6nm in diameter

•• Example: myosin in muscleExample: myosin in muscle

•• Interacts with Interacts with actinactin for movementfor movement

Cellular ExtensionsCellular Extensions

•• CiliaCilia

•• WhipWhip--likelike

•• Move substances in one direction across Move substances in one direction across

stationary cellsstationary cells

•• Example: Example: tracheatrachea

Cellular ExtensionsCellular Extensions

•• FlagellaFlagella

•• Substantially longer than ciliaSubstantially longer than cilia

•• Only example in human body: Only example in human body: spermsperm

Cellular ExtensionsCellular Extensions

•• MicrovilliMicrovilli

•• Very small, highly numerousVery small, highly numerous

•• Increase absorptive surface areaIncrease absorptive surface area

•• Example: Example: small intestinesmall intestine

NucleusNucleus

•• Genetic libraryGenetic library

•• Contains all instructions needed to build cell’s Contains all instructions needed to build cell’s

proteinsproteins

•• Dictates types, amounts of proteins to be madeDictates types, amounts of proteins to be made

•• Responds to extracellular signalsResponds to extracellular signals