BIOL164BIOL164

HumanBiologyHumanBiologyChCh3Cell3Cell

CellTheorystatesCellTheorystates

1.Livingorganismsarecomposedofoneormorecells.

2.Cellsarisefromthedivisionofpre‐exis:ngcells.

3.Cellsarethesmallestunitsoflife(thatperformallvitalphysiologicalfunc:ons).

There are over 200types of cells in thebody, each with aspecific structureand function(s)!

Whyarecellssosmall?Whyarecellssosmall?

• Needlargesurfacearea(supply)tovolume(demand)ra:o

Plasmamembrane(cellmembrane)Plasmamembrane(cellmembrane)

• =aphospholipidbilayerwithproteins,otherlipidsandcarbohydrates

• “Fluidmosaic”

PlasmamembranestructurePlasmamembranestructure

• Abouta50:50mixtureoflipidsandproteins

• Lipids:

• Phospholipids

• Cholesterol

• Proteins

MembraneProteinsMembraneProteins

• Anchoringproteins(CAMs=celladhesionmolecules)

• Recogni:onproteins(e.g.selfvs.foreignornon‐self)

• Enzymes

• Receptorproteins

• Carrierproteins

• Channelproteins

MembraneFuncFonsMembraneFuncFons

• Maintainsstructuralintegrityofcell

• Regulatesmovementofsubstancesinto/outofcell

• i.e.themembraneisselec.velypermeable

• Allowsrecogni:on

• ofselfvs.foreignornon‐self

• Allowscommunica:onbetweencells

• receptors

• Bindscellstogether

• CAMs

TransportTransport• Permeabilityreferstotheeasewith

whichsubstancescancrosstheplasma

(cell)membrane

• Nothingpassesthroughanimpermeable

membrane

• Anythingcanpassthroughafreelypermeable

membrane

• Ourplasma(cell)membranesare

selec%velypermeable(some:mescalled“semipermeable”)

• Permeabilityisaffectedbythe:

• Par:clesolubilityinlipid

• Par:clesizevs.proteinchannel(pore)size

• Par:cleelectricchargevs.localmembranechargeand/orchannelcharge

• Presenceofspecificproteincarriers(transporters)forthepar:cle

• Temperature

MembranetransportprocessesMembranetransportprocesses• Passiveprocesses:donotuseATPenergy

• Energyfortransportprovidedbyconstantrandommolecularmo:on(duetoheatenergypresent)

• Par:clesmovefromhighertolowerconcentra:on(i.e.downtheirconcentra.ongradient)un:lequilibrium(nonetmovementofpar:cles)isreached

• [high]→[low];“downhill”

• Examples:

• Simplediffusion

• Facilitateddiffusion

• Osmosis

• Ac%veprocesses:ATPenergyrequired

• Substancecanbemovedinoroutofcellregardlessofconcentra:ongradient

• Examples:

• AcFvetransport

• Endocytosis

• Exocytosis

SimplediffusionSimplediffusion

• Concentra:ondifference

• Small,lipid‐solublemolecules

• Passdirectlythroughmembrane

• O2,CO2,fa\yacids,steroids,

alcohol,lipid‐solublevitamins

(A,D,E,K)

FacilitateddiffusionFacilitateddiffusion

• Passthroughprotein

channels

• pores–(notshown)

• polarmolecules

• e.g.H20

• Chargedpar:cles

• ions,e.g.Na+,

Cl‐,etc.

• Largerpolarmoleculescan

passthroughprotein

carriers

• e.g.glucose,amino

acids

OsmosisOsmosis• Thediffusionofwater

• Throughasemi‐permeable

membrane

• Forlowtohighsolute

concentra:on

• Solu:ontypes

• hypertonic,

• isotonic,

• hypotonic

• refertothesolu:onthata

cellisin

• Cellswillbehavedifferentlyin

solu:onsofvarioustonici:es

AcFvetransportAcFvetransport

• moleculesare“pumped”againsttheirconcentra:ongradient

• [low]→ [high]

• Carrierproteinandenergy(ATP)required

• e.g.theNa+/K+exchangepump(notshownhere)

largermoleculesandvolumesofmateriallargermoleculesandvolumesofmaterial

• Material(e.g.bacteria,proteins,etc.)movesintooroutofcells

• inmembranousvesicles(sacs)

• ATPneededtomanipulateandmovevesiclesandcellmembrane

• Types(seenext3slidesforfigures):

• Endocytosis

• Phagocytosis(“cellea:ng”)

• Pinocytosis(“celldrinking”)

• Exocytosis

PhagocytosisPhagocytosis

PinocytosisPinocytosis

ExocytosisExocytosis

MovementofMovementofsubstancessubstancesacrosstheacrosstheplasmaplasma

membranemembrane

OrganellesOrganelles

• =intracellular“li\leorgans”thatcarryoutspecificvitalcelltasks

NucleusNucleus• Controlcenter(“brain”)ofcell

• Contains:

• Nucleolus:darkerregionthathelpsmakeribosomes

• DNAanditsassociatedproteinsintheformofchromaFn(chromosomeswhenchroma:niscondensed)

• 23pairsofchromosomesinhumans

RibosomesRibosomes

(a ribosome up close)

• Eachoneconsistsof2subunits

• MadeupofribosomalRNA(rRNA)+protein

• Func:on:sitesofproteinsynthesis

• Types:

• Freeribosomes:sca\eredthroughoutcytoplasm

• Makeproteinsforusewithincytoplasm

• Fixed(bound)ribosomes:a\achedtoendoplasmicre:culum

• Makeproteinsforexportorinclusionwithinmembranes

EndoplasmicreFculum(ER)EndoplasmicreFculum(ER)

• roughER

• ribosomesa\ached

• proteinsynthesis

or

• smoothER

• noribosomesa\ached

• Lipidsynthesis

• Detoxifica:onofalcohol,drugs

GolgicomplexGolgicomplex

• Sorts,modifies,packages,and

deliversproteinsinvesicles

• Formsnewplasma

membranecomponents

• Formslysosomes

GolgicomplexinacFonGolgicomplexinacFon