1. AEROBIC RESPIRATION
Amongotherbiomolecules,glucose hadbeenthe startingmaterial formetabolicprocessesthat
generate the energythatcellsuse iscalledCellularrespirationorAerobicrespiration.A processthat
extractsenergyfromfoodinthe presence of oxygen-obligateaerobes.The energythatisextractedis
usedto synthesizeATP-use tosupplyenergydirectlytocellstodrive chemical reactions.The glucose
that we consume inplantscan be convertedthroughmetabolicpathwaysinthe presence of oxygeninto
carbon dioxide,water,andenergy. The electronexchangesthatoccurthroughoutthese metabolic
pathwaysutilizedthe electroncarrierNAD+anditsotherformNADH. Thisisa dinucleotidewithabase
of Nicotinamide thatcanexisteitherasNAD+ witha positive charge nitrogenatom,orif reduceditcan
be NADH.This transferisfacilitatedbyanenzyme calledDehydrogenasethathelps catalyze the
breakdownof glucose.
Glycolysishappensinthe cytoplasmof the cell.Thisprocessbywhichglucose issplitintotwopieces is
calledpyruvate.ThisfirstpathwayisAnaerobic,meaningitdoesnotrequire oxygen.The firstfive-step
comprise the preparatoryphase,inwhichone molecule of glucose producestwomoleculesof GADP,
thiswill costtwoATP. Thenthe lastfive stepsmake upthe payoff phase,inwhicheachmolecule of
GADP will be converted intopyruvateproducingtwoATP,foratotal of four meaningthe netenergy
productionfromone molecule of glucose istwoATP.
The citric Acid Cycle isthe process thatoccurs in the cell of mitochondria,whichare eukaryoticcell
organelles.Mitochondriawere once separateorganismsbecause of the respiratoryabilitiesthey
possessed. Itbeginswiththe pyruvate moleculethatwasgeneratedinthe cytoplasmduringglycolysis,
whichwill nowenterthe mitochondrial matrix tofindCoenzyme A.Inthe presence of NAD+pyruvate
will undergo:Decarboxylation,OxidationbyNAD+,andattachmenttoCoenzyme A.generatingAcetyl
CoA that will thenenterCitricAcidCycle alsoknownasthe Krebscycle or TricarboxylicCycle whichhas
eight-steps.
2. Oxidative Phosphorylationgeneratesthe mostATP.Thispathwayutilizes anelectrontransportchain
that happensinthe innermembrane of the mitochondrion.ReferredtoasProteinComplexesI-IV.One
compoundinthe electrontransportchainthat isnot proteinandthat's Ubiquinone (asmall
hydrophobicmolecule thatismobile withinthe membrane alsoknownasCoenzyme Q)
A proteincomplex componentthat synthesizes ATPiscalled ATPsynthase,because the proton
concentrationbecomesgreaterinthe intermembrane, andthe protonwill move withthe gradientto re-
enterthe mitochondrial matrix andthe onlyroute available isthroughATPsynthase thisprocessis
calledchemiosmosis (Proton-motiveforce).Protonsspinthe rotorwhichallowsthe knobto catalyze
ATP synthase withthe NADHandFADH2 that are generatedfromsinglemoleculesof glucose,we can
get26 or 28 ATP.So thisis the pathwaythatgeneratesthe majorityof cellularenergy.
Electron Transport Chainis the laststepin aerobicrespiration.Inthisphase, large amountsof ATP
moleculesare producedbytransferringthe electronsfromNADHandFADH.A single molecule of
glucose createsa total of 34 ATPmolecules
Fermentationisa metabolicprocessthatinvolvesthe utilizationof enzymestocause chemical changes
inorganic substrates.Itisdefinedasthe processof extractingenergyfromcarbohydratesinthe absence
of oxygen.Because anaerobicrespirationandfermentationdonotinclude anytype of respiration,they
do notnecessitate the usage of oxygen. BecauseglycolysisrequiresnooxygenandproducestwoATP
moleculesperglucosemolecule,itisalwaysthe firststep.
3. Lactic Acid Fermentationisa metabolicprocessbywhichglucose orother six-carbonsugars(also,
disaccharidesof six-carbonsugars,e.g.sucrose orlactose) are convertedintocellularenergyandthe
metabolite lactate,whichis the lacticacidinsolution.
Alcohol FermentationA biological process thatconvertssugarssuchas glucose,fructose,andsucrose
intocellularenergy,producingethanolandcarbondioxide asby-products.
4. TRANSPORT MECHANISM
Cell transportreferstothe movementof substancesacrossthe cell membrane.Probably
the most importantfeature of acell'sphospholipid membranesisthattheyare selectivelypermeable.A
membrane thatisselectivelypermeable,orsemipermeable,hascontrol overwhatmoleculesorionscan
enteror leave the cell. The movementof asubstance acrossthe cell membrane isknownascell
transport.The substance can move eitherinorout of the cells.Sometimesthe solutionmovesthrough
the phospholipidbilayerorelse,itssubstance iscombinedwithproteintopassthroughthe cell
membrane. Thisfeature allowsacell tocontrol the transport of materials,asdictatedbythe cell's
function.The permeabilityof amembrane isdependentonthe organizationandcharacteristicsof the
membrane lipidsandproteins.
Passive transport isa type of membrane transportinwhichchemicalsare movedacross cell membranes
withoutthe need forenergy.Passive transportusesthe secondlaw of thermodynamicstodrive the
movementof substancesacrosscell membranesratherthancellularenergy,asactive transportdoes.
No energyisneededbecause the substances are movingfromanarea where theyhave ahigher
concentrationtoan area where theyhave alowerconcentration.
Simple diffusionoccurswhena particle movesfromahigherto a lowerconcentrationwithoutany
assistance.The concentrationgradient'sdirectional movementispassive.The moleculesonbothsides
of the cell membrane reachanequilibriumwhere nonetmovementof moleculesisdetectedafterthe
moleculesare uniformlydispersed.
Facilitateddiffusionisthe transferof substancesacrossa biological membraneviaaconcentration
gradientanda carrier molecule isknownasfacilitateddiffusion.Large ionsandpolarmoleculesare
dissolvedinwaterandmovedacrossthe cell membrane inaspecificandpassive mannerduringassisted
diffusion. -The transportreliesonmolecularbindingbetweenthe cargoandthe membrane-embedded
channel or carrierprotein.The rate of facilitateddiffusionissaturable concerningthe concentration
difference betweenthe twophases;unlike freediffusionwhichislinearinthe concentrationdifference.
Next,active transporthappensthroughvesicle movement.It’seitherEndocytosisatExocytosis.
Endocytosisbringsitemsintothe cell while Exocytosispushesthemoutof the cell.Endocytosisand
exocytosisare the bulk transportmechanismsusedineukaryotes.Asthese transportprocessesrequire
energy,theyare knownasactive transportprocesses.
EndocytosisProcessby whichcellsingestexternal fluid,macromolecules, orotherlarge particles.
Endocytosisbringsitemsintothe cell.
Phagocytosis- “Phago” meansto eat.Thisis usedbyWhite BloodCellslike macrophagesand
neutrophilswhichpatrol the bodylookingforDebris, Bacteria,anddeadcellstoeat.Thisiswhere large
particlesorwhole cellsare ingested.
Pinocytosis- isa processby whichthe cell takesinthe fluidsalongwithdissolvedsmall molecules.
“Pino”means“to drink”.
ExocytosisProcessby whicha substance isreleasedfromacell througha vesicle thattransportsittothe
cell surface andfuseswiththe cell membrane.Exocytosispushessubstancesoutof the cells.
5. Osmosisis a passage of watermoleculesthroughaselectivelypermeable membrane.The nettransfer
of watermoleculesfromasolutionwithahighwaterpotential toa regionwithalow waterpotential
across a partiallypermeable barrier.Waterwillbe drawninbya cell witha lowernegative water
potential,althoughthisisdependentonotherparameterssuchas solute potential andpressure
potential.the isotonicsolution,hypotonicsolution,andhypertonicsolutionare the three varietiesof
Osmosissolutions.
The 3 Varieties ofosmosis
Isotonic watermoleculesstill travelbetweenthe solutionsinanisotonicsolution,butthe ratesare the
same in bothdirections,ensuringthatwatermovementisbalancedbothinside andoutside the cell.
Hypotonic solutioniswhenthe concentrationof solute outsidethe cell islowerthanthe concentration
inside the cell.Watergoes enterthe cell downthe concentrationgradientinhypotonicsolutions.The
cell mayswell asa resultof this.Animal cells,forexample,couldexplodeinthisfluidsince theylack a
cell wall.
Hypertonic If the solute concentrationishigherthanthe concentrationinside the cell.Thewaterwill
migrate outof the cell ina hypertonicsolution,causingittoshrink.
6. ENZYMES
A substance thatacts as a catalystin livingorganisms,regulatingthe rate at whichchemical
reactionsproceedwithoutitselfbeingalteredinthe process. The majority of enzymesare proteinswith
catalyticcapabilitiescrucial to performingdifferentprocesses.Metabolicprocessesandother chemical
reactionsinthe cell are carried outby a set of enzymesthatare necessarytosustainlife.Enzymescan
be definedasbiologicalpolymersthatcatalyze biochemical reactions.Foundinall tissuesandfluidsof
the body.The macromolecularcomponentsof all enzymesconsistof protein,exceptinthe classof RNA
catalystscalledribozymes.The wordribozyme isderivedfromthe ribonucleicacidenzyme.
How Do EnzymesWork?
The “lock and key”model wasfirstproposedin1894. Inthismodel,anenzyme’sactive site isa
specificshape,andonlythe substrate willfitintoit,like alockandkey.Thismodel hasnow been
updatedandis calledthe induced-fitmodel.Inthismodel,the active site changesshape asitinteracts
withthe substrate.Once the substrate isfullylockedinandinthe exactposition,the catalysiscanbegin.
CLASSES OF ENZYME
The enzyme Oxidoreductase catalyzesthe oxidationreactionwherethe electronstendtotravel
fromone form of a molecule tothe other. Anenzyme thatcatalyzesthe transferof electronsfromone
module.Commonlycalleddehydrogenases. These catalyzeoxidationandreductionreactions,e.g.
pyruvate dehydrogenase, catalyzingthe oxidation of pyruvate toacetyl coenzyme.
The Transferases enzymeshelpinthe transportationof the functional groupamongacceptors
and donormolecules. These catalyze transferringof the chemical groupfromone toanothercompound.
An example isatransaminase,whichtransfersanaminogroupfromone molecule toanother.Helpin
the transportationof the functional groupamongacceptorsand donormolecules.
Hydrolasesare hydrolyticenzymes,whichcatalyze the hydrolysisreactionbyaddingwaterto
cleave the bondandhydrolyze it. Theycatalyze the hydrolysisof abond.For example,the enzyme
pepsinhydrolyzespeptidebondsinproteins.
Lyase addswater,carbon dioxide,orammoniaacrossdouble bondsor eliminatesthese to
create double bonds. These catalyze the breakageof bondswithoutcatalysis.
Isomerase enzymescatalyze the structural shiftspresentinamolecule,thuscausing achange
inthe shape of the molecule. Theycatalyze the formationof anisomerof a compound.
The Ligases enzymesare knowntocharge the catalysisof a ligationprocess. Ligasescatalyzethe
associationof twomolecules.Forexample,DNA ligasecatalyzesthe joiningof twofragmentsof DNA by
forminga phosphodiesterbond.
