This document discusses the key concepts of life and living processes. It defines the cell as the basic unit of life and describes the main differences between prokaryotic and eukaryotic cells. The main components of cells are then outlined, including the cell membrane, cytoplasm, organelles like the nucleus, mitochondria, chloroplasts, and lysosomes. The seven main life processes that characterize living things are identified as movement, respiration, sensitivity, growth, excretion, reproduction, and nutrition.

1. Primeasia University
Department of Public Health Nutrition
AssignmentTopics:
Topics:ConceptofLifeAndLivingProcess
Prepared by _Md.ZiaUddin
ID NO: 131-485-034
Submitted to_
Farzana sultanaBari
SeniorLecturer
DepartmentOfPublicHealthNutrition

2. #Z477
Conceptof Life
A cell isthe smallestunitof life thatcanreplicate independently, andcellsare oftencalledthe "building
blocksof life"The cell (fromLatincella,meaning"small room") isthe basicstructural,functional,and
biological unitof all known livingorganisms
Cells:
All livingthingsare made uptocellswhichare unicellularormulticellularorboth
Cellsconsistof cytoplasmenclosedwithinamembrane,whichcontainsmany biomolecules such
as proteins andnucleicacids.Organismscanbe classifiedasunicellular(consistingof asingle cell;
includingbacteria) ormulticellular(includingplantsandanimals).While the numberof cellsinplants
and animals variesfromspeciestospecies,humanscontainmore than10 trillion(1012) cells.Mostplant
and animal cellsare visibleonlyunderamicroscope,withdimensionsbetween1and 100 micrometres,
The cell was discoveredby RobertHooke in1665
Cellsare of two types,eukaryotic,whichcontainanucleus,andprokaryotic,whichdonot.Prokaryotes
are single-celledorganisms,while eukaryotescanbe eithersingle-celledormulticellular.

3. Prokaryotic cells
Prokaryoticcellswere the firstformof life onEarth,characterisedbyhavingvital biological
processes includingcell signalingandbeingself-sustaining.Theyare simplerandsmallerthaneukaryotic
cells,andlackmembrane-boundorganellessuchasthe nucleus.Prokaryotesinclude twoof the domains
of life,bacteriaandarchaea.The DNA of a prokaryoticcell consistsof asingle chromosome thatisin
directcontact withthe cytoplasm.The nuclearregioninthe cytoplasmiscalledthe nucleoid.
Eukaryotic cells
Plants,animals,fungi,slimemoulds,protozoa,andalgae are all eukaryotic.These cellsare aboutfifteen
timeswiderthana typical prokaryote andcan be as much as a thousandtimesgreaterinvolume.The
maindistinguishingfeature of eukaryotesas comparedtoprokaryotesis compartmentalization: the
presence of membrane-boundorganelles (compartments) inwhichspecificmetabolicactivitiestake
place.
Subcellularcomponents
All cells,whetherprokaryoticoreukaryotic,have amembrane thatenvelopsthe cell,regulateswhat
movesinand out(selectivelypermeable),andmaintainsthe electricpotential of the cell.Insidethe
membrane,the cytoplasmtakesup mostof the cell'svolume.There are alsootherkinds
of biomolecules incells.Thisarticle liststheseprimarycomponentsof the cell,thenbrieflydescribes
theirfunction.
Membrane
The cell membrane,orplasmamembrane,isabiological membrane thatsurroundsthe cytoplasmof a
cell.Inanimals,the plasmamembrane isthe outerboundaryof the cell,while inplantsandprokaryotes
it isusuallycoveredbya cell wall.Thismembrane servesto separate andprotecta cell fromits
surroundingenvironmentandismade mostlyfroma double layerof phospholipids,which
are amphiphilic(partly hydrophobicandpartly hydrophilic).Hence,the layeriscalledaphospholipid
bilayer.The membrane issaidtobe 'semi-permeable',inthatitcan eitherletasubstance
(moleculeorion) passthroughfreely,passthroughtoa limitedextentornotpassthroughat all.
Cytoskeleton
The cytoskeletonactstoorganize andmaintainthe cell'sshape;anchorsorganellesinplace;helps
duringendocytosis,the uptake of externalmaterialsbyacell,and cytokinesis,the separationof
daughtercellsaftercell division;andmovespartsof the cell inprocessesof growthand mobility.The
eukaryoticcytoskeletoniscomposedof microfilaments,intermediate filaments andmicrotubules.
Organelles
Organellesare partsof the cell whichare adaptedand/orspecializedforcarryingoutone or more vital
functions,analogoustothe organsof the human body(suchas the heart,lung,and kidney,witheach
organ performingadifferentfunction).Botheukaryoticandprokaryoticcellshave organelles,but
prokaryoticorganellesare generallysimplerandare not membrane-bound.
There are several typesof organellesinacell.Some (suchas the nucleus andgolgi apparatus) are
typicallysolitary,while others(suchas mitochondria,chloroplasts,peroxisomesandlysosomes) canbe
numerous(hundredstothousands).The cytosol isthe gelatinousfluidthatfillsthe cell andsurrounds
the organelles.

4. Eukaryotic
Human cancer cellswithnuclei (specificallythe DNA) stainedblue.The central andrightmostcell are
ininterphase,sothe entire nucleiare labeled.The cell onthe leftisgoingthrough mitosisanditsDNA
has condensed.
Cell nucleus:A cell'sinformationcenter,the cell nucleus isthe mostconspicuousorganelle foundin
a eukaryoticcell.Ithousesthe cell's chromosomes,andisthe place where almostall DNA replication
and RNA synthesis(transcription) occur.The nucleusisspherical andseparatedfromthe cytoplasmbya
double membrane calledthe nuclearenvelope.The nuclearenvelope isolatesandprotectsacell'sDNA
fromvariousmoleculesthatcouldaccidentallydamage itsstructure orinterferewithitsprocessing.
Duringprocessing, DNA istranscribed,orcopiedintoaspecial RNA,calledmessengerRNA (mRNA).This
mRNA isthentransportedoutof the nucleus,where itistranslatedintoaspecificprotein molecule.
The nucleolus isaspecializedregionwithinthe nucleuswhereribosomesubunitsare assembled.In
prokaryotes,DNA processingtakesplace inthe cytoplasm.
Mitochondriaand Chloroplasts:generate energyforthe cell. Mitochondriaare self-replicating
organellesthatoccurin variousnumbers,shapes,andsizesinthe cytoplasmof all eukaryotic
cells.[3] Respiration occursinthe cell mitochondria,whichgenerate the cell'senergyby oxidative
phosphorylation,usingoxygentorelease energystoredincellularnutrients(typicallypertaining
to glucose) togenerate ATP.Mitochondriamultiplyby binaryfission,like prokaryotes.Chloroplastscan
onlybe foundinplantsand algae,andtheycapture the sun'senergytomake carbohydrates
throughphotosynthesis.
Endoplasmicreticulum:The endoplasmicreticulum (ER) isatransportnetworkformoleculestargeted
for certainmodificationsandspecificdestinations,ascomparedtomoleculesthatfloatfreelyinthe
cytoplasm.The ER has twoforms:the roughER, whichhas ribosomesonitssurface thatsecrete proteins
intothe ER, and the smoothER, whichlacks ribosomes. The smoothERplaysa role incalcium
sequestrationandrelease.
Golgi apparatus: The primaryfunctionof the Golgi apparatusis to processandpackage
the macromolecules suchas proteins andlipidsthatare synthesizedbythe cell.
Lysosomesand Peroxisomes:Lysosomes containdigestive enzymes (acidhydrolases).Theydigest
excessorworn-outorganelles,foodparticles,andengulfed virusesorbacteria.Peroxisomes have
enzymesthatridthe cell of toxicperoxides.The cell couldnothouse these destructiveenzymesif they
were notcontainedina membrane-boundsystem.
Centrosome:the cytoskeletonorganiser:The centrosome producesthe microtubules of acell – a key
componentof the cytoskeleton.Itdirectsthe transportthroughthe ER and the Golgi apparatus.
Centrosomesare composedof two centrioles,whichseparate during celldivision andhelpinthe
formationof the mitoticspindle.A single centrosome ispresentinthe animal cells.Theyare alsofound
insome fungi andalgae cells.
Vacuoles:Vacuoles sequesterwaste productsandinplantcellsstore water.Theyare oftendescribedas
liquidfilledspace andare surroundedbya membrane.Some cells,mostnotably Amoeba,have
contractile vacuoles,whichcanpumpwaterout of the cell if there istoomuch water.The vacuolesof
plantcellsandfungal cellsare usuallylargerthanthose of animal cells.

5. Eukaryoticand prokaryotic
Ribosomes:The ribosome isa large complex of RNA andprotein molecules. Theyeachconsistof two
subunits,andact as an assemblyline where RNA fromthe nucleusisusedtosynthesiseproteinsfrom
aminoacids.Ribosomescanbe foundeitherfloatingfreelyorboundtoa membrane (the rough
endoplasmaticreticulumineukaryotes,orthe cell membrane inprokaryotes).
Cellularprocesses
Cell growth and Metabolism:
Betweensuccessive cell divisions,cellsgrow throughthe functioningof cellular metabolism.Cell
metabolismisthe processbywhichindividual cellsprocessnutrientmolecules.Metabolismhastwo
distinctdivisions: catabolism,inwhichthe cell breaksdowncomplexmoleculestoproduce energy
and reducingpower,andanabolism,inwhichthe cell usesenergyand reducingpowertoconstruct
complex moleculesandperformotherbiological functions.Complex sugarsconsumedbythe organism
can be brokendownintosimplersugarmoleculescalled monosaccharides suchasglucose.Once inside
the cell,glucose isbrokendowntomake adenosine triphosphate (ATP),amoleculethatpossesses
readilyavailable energy,throughtwodifferentpathway.
Living Process
In science,the broadestgroupingsare livingandnon-living.Alllivingthingsshare life processessuchas
growthand reproduction.Mostscientistsuse sevenlife processesorcharacteristicstodetermine
whethersomethingislivingornon-living.
All livingthingsare calledorganisms,bothplantsandanimalsare livingorganisms.Buthow we decide
whethersomethingisliving ornon-livingdependson 7 life processes.
1. Movement
Both animalsandplantshave the abilitytomove.Plantsare rootedandmove slowlyastheygrow.Their
roots move downintothe soil andtheirstemsmove uptowardsthe light.Animalsonthe other hand
move quicklyandcan move theirentire bodies.Theycanmove insearchof food,shelterorto avoid
danger.
2. Respiration
Respirationisthe processof extractingenergyoutof the foodwe eat.All livingthingsrespirebecause
theyneedenergyto grow,to replace wornoutparts and to move.Respirationtakesplace inthe
mitochondriaof the cell.There are twotypesof respiration,withandwithoutoxygen.Aerobic
respirationusesoxygenandreleasesalarge amountof energy.Anaerobicrespiration doesnotrequire
oxygenandreleasesasmalleramountof oxygen.
3. Sensitivity
All livingorganismsare sensitive,thismeansthattheyhave anawarenessof changesintheir
environment.Animalsrespondquicklytostimuli suchasheat,light,sound,touch andchemicalswhich
have taste and smell.Onthe otherhandplantsgenerallyappearlesssensitive andtheirresponse is
slower.Plantsrespondtolightbymovingtheirleavestowardsit,the flowersof some plantsopeninthe
morningandclose at nightwhenitis dark.Some plants,however,dorespondquicklysuchasthe Venus
flytrapresponse totouch.
4. Growth

6. All livingorganismsgrow.Plantscontinuegrowingthroughouttheirlives.Animalsstopgrowingonce
theyreach adulthood.Evenwhengrowthstops,materialswithinananimal’sbodyare still being
replacedfromitsfood.
5. Excretion
All livingthingsmake waste productsthesecanbe uselessorharmful toitand therefore needtobe got
rid of.Excretionisthe processof gettingridof metabolic waste.Plantsstore waste substancesintheir
leaves,the waste isremovedwhentheirleavesfall off.Animalsbreathe outwaste carbondioxide,other
waste substancesleave the bodyinurine andsweat.Note:Gettingridof faecesorundigestedfoodis
not excretionbutejection.
6. Reproduction
All livingthingsmustproduce offspringlike themselvesinorderfortheirspeciestosurvive.Thisisthe
processknownas reproduction.Plantsproduceseedsthatgive rise tonew plantsof the same species.
Animalslayeggsorhave babies.Reproductioncanbe of twotypes,Sexual whichinvolvestwoparents
and the unionof two gametesandAsexual where one parentcanreproduce itself.
7. Nutrition
Nutritionisneededforenergyandgrowth,bothplantsandanimalsneedfood.Plantsare able tomake
theirownfoodby photosynthesis.Theyuse sunlighttoturnsimple moleculeslikecarbondioxide and
waterintomore complex carbohydrate molecules.Animalsare unable tomake theirownfoodsorely
on otherplantsand other animalsfortheirnutrition.Animalstake incomplex substancesandbreak
themdownintosmall,simple,soluble moleculeswhichcanbe usedforenergyandgrowth.
References:
http://www.srmuniv.ac.in/sites/default/files/downloads/Introduction_To_Biochemistry.pdf
https://www.sciencelearn.org.nz/resources/14-characteristics-of-living-things
http://www.passmyexams.co.uk/GCSE/biology/life-processes.html
http://www.fsg.rnu.tn/imgsite/cours/Life%20processes%20(R%C3%A9par%C3%A9).pdf
https://en.wikipedia.org/wiki/Cell_(biology)