Cellsarethebasicunitsoflife.Everylivingthingismadeofcells.Humanshavemanycells.Plantshavecellstoo.Cellsareverysmall.Wecannotseethemwithoureyesalone.Weneedamicroscopetoseethem.Microscopesmakesmallthingslookbig.

Acellhasdifferentparts.Eachparthasajob.Theouterpartisthecellmembrane.Itislikeaskin.Itholdsthecelltogether.Itletsgoodthingsin.Itkeepsbadthingsout.Insidethecellthereisajelly-likesubstance.Itiscalledcytoplasm.Manyimportantthingsfloatinthecytoplasm.

Thenucleusisaveryimportantpart.Itislikethebrainofthecell.Itcontrolswhatthecelldoes.ThenucleusholdsDNA.DNAislikeasetofinstructions.Ittellsthecellhowtogrow.Ittellsthecellhowtowork.Ittellsthecellhowtomakenewcells.

Mitochondriaareanotherpart.Theyarelikepowerplants.Theytakeinfoodandmakeenergy.Thecellneedsenergytodoallitsjobs.Ribosomesaretinyparts.Theymakeproteins.Proteinsarethebuildingblocksforthebody.Theyhelpthecellrepairitself.Theyhelpthebodygrow.

Cellsinplantshaveextraparts.Theyhaveacellwall.Itisoutsidethemembrane.Itisstiffandstrong.Itgivestheplantcellitsshape.Ithelpsplantsstanduptall.Plantcellsalsohavechloroplasts.Thesepartsaregreen.Theycontainchlorophyll.Chlorophyllhelpsplantsusesunlight.Theyusesunlighttomakefood.Thisprocessiscalledphotosynthesis.

Cellscomefromothercells.Thisisakeyideainbiology.Acellgrows.ItmakesacopyofitsDNA.Itdividesintotwocells.Thisiscalledcelldivision.Thetwonewcellsarejustliketheparentcell.Thisishowlivingthingsgrow.Thisishowbodiesrepaircutsandbrokenbones.

Notallcellsarethesame.Thehumanbodyhasmanycelltypes.Musclecellsarelongandcancontract.Theyhelpusmove.Nervecellsarelikelongwires.Theycarrysignalsinthebody.Theyhelpusthinkandfeel.Bloodcellsareround.Redbloodcellscarryoxygen.Whitebloodcellsfightgerms.Skincellsareflatandlayered.Theyprotectourbodyfromtheoutsideworld.

Cellsworktogether.Cellsofthesametypeformatissue.Muscletissueismadeofmusclecells.Nervetissueismadeofnervecells.Differenttissuesworktogethertoformanorgan.Theheartisanorgan.Ithasmuscletissue.Ithasnervetissue.Ithasbloodtissue.Organsworktogetherinsystems.Theheartandbloodvesselsformthecirculatorysystem.Allsystemsworktogethertomakealivingorganism.

Sometimesthingsgowrongincells.DNAinstructionscangetdamaged.Thiscanhappenbychance.Itcanhappenbecauseofharmfulthingslikesomechemicalsorradiation.AcellwithdamagedDNAmaystarttodividewithoutcontrol.Itcanmakemanybadcells.Thiscanformalumpcalledatumor.Thisishowcancerbegins.Scientistsstudycellstounderstandcancer.Theylookforwaystofixdamagedcells.Theylookforwaystostopbadcellsfromgrowing.

Wecanlearnalotfromcells.Scientistsgrowcellsinlabs.Theyusespecialdishesandwarmrooms.Theygivecellsfoodandnutrients.Studyingcellsinlabsiscalledcellculture.Ithelpsustestnewmedicines.Ithelpsusunderstanddiseases.Itisaveryimportanttoolforbiologyandmedicine.

Cellsareamazing.Theyaretinyfactories.Theyarebuildingblocks.Theyarethestartofeveryplantandanimal.Lifedependsontheworkofcells.Everybreathyoutakeusesmusclecells.Everythoughtyouhaveusesnervecells.Thefoodyoueatisbrokendownbyyourbody'scells.Theenergyyouuseismadeinyourcells.

Thestudyofcellsiscellbiology.Itisamajorpartofscience.Scientistskeeplearningnewthingsaboutcells.Theyusebettermicroscopesnow.Theycanseethetinypartsinsidecellsveryclearly.Theycanevenstudysinglemoleculesinsideacell.Thisknowledgehelpsdoctors.Ithelpsfarmersgrowbettercrops.Ithelpsusunderstandlifeitself.

Cellsareallaroundus.Theyareintheair.Theyareinthesoil.Theyareinthewater.Bacteriaaresinglecells.Theycanbehelpful.Somebacteriainourstomachhelpusdigestfood.Theycanbeharmful.Somebacteriamakeussick.Yeastisasinglecell.Peopleuseyeasttomakebreadandbeer.

Ourworlddependsonthehealthofcells.Whenplantcellsarehealthy,cropsgrowwell.Whenanimalcellsarehealthy,animalsarestrong.Whenourhumancellsarehealthy,wefeelgood.Wecankeepourcellshealthy.Weneedtoeatgoodfood.Goodfoodgivescellstherightmaterials.Weneedtodrinkwater.Waterhelpscellsdotheirwork.Weneedtorest.Cellsrepairthemselveswhenwesleep.

Thestoryofcellsisthestoryoflife.Fromonecell,awholepersoncangrow.Thatfirstcellhasalltheinstructionsneeded.Itdividesagainandagain.Cellschangeintodifferenttypes.Theyformtissuesandorgans.Inninemonths,asinglecellbecomesababywithtrillionsofcells.Thisprocessiswonderful.Itshowsthegreatpowerhiddeninsideatinycell.