Cell anatomy

Anatomy

2. •Cellsarethestructuralunitsofalllivingthings.
Allcellsarisefromexistingcellsbytheprocess
ofcelldivision,inwhichonecelldividesinto
twoidenticalcells.
•TheEnglishscientistRobertHookefirst
observedplantcellswithacrudemicroscopein
thelate1600s.Then,inthe1830stwoGerman
scientists,MatthiasSchleidenandTheodor
Schwann,proposedthatalllivingthingsare
composedofcells.

3. Cell diversity

4. PARTS OF A CELL
Ahumancellhasthreemainparts:
•Theplasmamembrane:theouter
boundaryofthecell.
•Thecytoplasm:theintracellularfluid
packedwithorganelles,smallstructures
thatperformspecificcellfunctions.
•Thenucleus:anorganellethatcontrols
cellularactivities.Thenucleusliesnearthe
cell’scenter.

6. A.THE PLASMA MEMBRANE
•Theplasmamembranedefinestheextent
ofacell,therebyseparatingtwoofthe
body’smajorfluidcompartmentsthe
intracellularfluidwithincellsandthe
extracellularfluid(ECF)outsidecells.The
plasmamembraneenclosescellcontents,
mediatesexchangeswiththeextracellular
environment,andplaysaroleincellular
communication.

8. Structure
TheFluidMosaicModel
•Thefluidmosaicmodelofmembrane
structuredepictstheplasmamembraneas
anexceedinglythin(7–10nm)structure
composedofadoublelayeroflipid
moleculeswithproteinmoleculesdispersed
init.
•Theproteinswhichfloatinthefluidlipid
bilayer,formaconstantlychangingmosaic
pattern.

9. The Glycocalyx
•Plasma membrane contains a carbohydrate
rich area at the cell surface called glycocalyx.
Cell junctions.
•An epithelial cell is shown joined to adjacent
cells by three common types of cell junctions.

10. 1.TightJunctions:Impermeablejunctions
preventmoleculesfrompassingthroughthe
intercellularspace.
2.Desmosomes:Anchoringjunctionsbind
adjacentcellstogetherlikeamolecular
“Velcro”andhelpformaninternaltension
reducingnetworkoffibers.
3.Gapjunctions:Communicatingjunctions
allowionsandsmallmoleculestopassfor
intercellularcommunication

12. B.THE CYTOPLASM
Thecellularmaterialbetweentheplasma
membraneandthenucleus,isthesiteofmost
cellularactivities.Itconsistsofthreeelements:
–Thecytosol
–Organelles
–Inclusions.

13. 1.Thecytosol:itistheviscous,semitransparent
fluidinwhichtheothercytoplasmicelements
aresuspended.
2.Theorganellesarethemetabolicmachinery
ofthecell.Eachtypeoforganellecarriesouta
specificfunctionforthecell.
3.Theinclusionsarechemicalsubstancesthat
mayormaynotbepresent,dependingoncell
type.

14. Mitochondria
•Rodlike, double-
membranestructures;
inner membrane
foldedintoprojections
calledcristae.
•SiteofATPsynthesis;
powerhouseofthecell.

15. Ribosomes
•Dense particles
consistingoftwo
subunits, each
composed of
ribosomalRNAand
protein.Freeor
attachedtorough
endoplasmic
reticulum.
•Thesitesofprotein
synthesis.

16. Rough endoplasmic reticulum
•Membranous system
enclosingacavity,the
cistern,and coiling
throughthecytoplasm.
Externallystuddedwith
ribosomes.
•Sugargroupsareattached
toproteinswithinthe
cisterns.Proteinsare
boundinvesiclesfor
transporttotheGolgi
apparatusandothersites.
•Externalfacesynthesizes
phospholipids.

17. Smooth endoplasmic reticulum
•Membranoussystem
ofsacsandtubules;
freeofribosomes.
•Siteoflipidandsteroid
(cholesterol)
synthesis, lipid
metabolism,anddrug
detoxification.

18. Golgi apparatus
•Astackofflattened
membranes and
associatedvesicles
closetothenucleus.
•Packages,modifies,
and segregates
proteinsforsecretion
fromthecell,inclusion
inlysosomes,and
incorporationintothe
plasmamembrane.

19. Peroxisomes
•Membranoussacsof
catalaseandoxidase
enzymes.
•Theenzymesdetoxify
anumberoftoxic
substances.Themost
importantenzyme,
catalase,breaksdown
hydrogenperoxide.

20. Lysosomes
•Membranous sacs
containing acid
hydrolases.
•Sites of intracellular
digestion.

21. Microtubules
•Cylindricalstructuresmadeoftubulin
proteins.
•Supportthecellandgiveitshape.Involved
inintracellularandcellularmovements.
Formcentriolesandciliaandflagella,if
present.

22. Microfilaments
•Finefilamentscomposedoftheprotein
actin.Involvedinmusclecontractionand
othertypesofintracellularmovement,help
formthecell’scytoskeleton.

23. Intermediate filaments
•Proteinfibers;compositionvaries.The
stablecytoskeletalelements;resist
mechanicalforcesactingonthecell.

24. Centrioles
•Paired cylindrical
bodies,eachcomposed
ofninetripletsof
microtubules.
•Organizeamicrotubule
networkduringmitosis
(celldivision)toform
thespindleandasters.
Formthebasesofcilia
andflagella.

25. Inclusions
•Inclusionsincludesstorednutrientssuch
aslipiddropletsandglycogengranules,
proteincrystals,pigmentgranules.Storage
fornutrients,wastes,andcellproducts.

26. Cellular Extensions
•The major cellular extensions are
1.Cilia
2.Flagellum
3.Microvilli

27. 1.Cilia
•Short cell-surface
projections;eachcilium
composedofninepairs
of microtubules
surroundingacentral
pair.
•Coordinatedmovement
createsaunidirectional
currentthatpropels
substancesacrosscell
surfaces.

28. 2.Flagellum
•Likeacilium,but
longer;onlyexample
inhumansisthe
spermtail.Propelsthe
cell.

29. 3.Microvilli
•Tubularextensionsof
theplasmamembrane;
containabundleof
actin filaments.
Increasesurfacearea
forabsorption.

30. C.NUCLEUS
•Thenucleusisasphericaloroval-shaped
structurethatusuallyisthemostprominent
featureofacell.Surroundedbythenuclear
envelope;containsfluidnucleoplasm,
nucleoli,andchromatin.
•Controlcenterofthecell;responsiblefor
transmittinggeneticinformationand
providingtheinstructionsforprotein
synthesis.

32. Structure of the Nucleus
1.The nuclear envelope
2.Nucleoplasm
3.Chromatin
4.The nucleolus

33. Nuclear Envelope
•Thenuclearenvelopeisadouble-layered
membraneperforatedwithpores,which
controltheflowofmaterialgoinginand
outofthenucleus.
•Theouterlayerisconnectedtothe
endoplasmicreticulum,communicating
withthecytoplasmofthecell.The
exchangeofthelargemolecules(protein
andRNA)betweenthenucleusand
cytoplasmhappenshere.

34. Nucleoplasm
•Ajelly-like(mademostlyofwater)matrix
withinthenucleus
•Alltheothermaterials“float”inside
•Helpsthenucleuskeepitsshapeand
servesasthemedianforthe
transportationofimportantmolecules
withinthenucleus

35. Chromatin
•Chromatinappearsasafine,unevenly
stainednetwork,butspecialtechniques
revealitasasystemofbumpythreads
weavingthroughthenucleoplasm.
–Chromatiniscomposedofapproximately
–30%DNA,ourgeneticmaterial
–60%globularhistoneproteinswhichpackage
andregulatetheDNA
–10%RNAchains,newlyformedorforming

36. Chromosomes
•ChromosomescontainDNAinacondensedform
attachedtoahistoneprotein.
•ChromatiniscomprisedofDNA.Therearetwo
typesbasedonfunction.
–Heterochromatin: highly condensed,
transcriptionallyinactivemostlylocated
adjacenttothenuclearmembrane
–Eurochromatin:delicate,lesscondensed
organizationofchromatin,locatedina
transcribingcell

37. Functions
•Thenucleusisoftencomparedtothe
“commandcenter,”asitcontrolsall
functionsofthecell.
•Itisimportantinregulatingtheactions
ofthecells.
•Itplaysanimportantpartincreating
thecell’sproteins.
•Itisinvolvedinimportantprocesses
dealingwithDNAandothergenetic
molecules.

38. DNA
•DNAordeoxyribonucleicacid,contains
theinformationneededforthecreation
ofproteins(whichincludeenzymesand
hormones)andisstoredinthenucleus,
asalreadysaid,intheformofchromatin
orchromosomes.
•ThenucleusisthesiteofDNA
duplication,whichisneededforcell
division(mitosis)andorganism
reproductionandgrowth.

40. RNA
•RNA are made fromtheDNA template:
1.MessengerRNA(mRNA)directsthesynthesis
ofaprotein.
2.RibosomalRNA(rRNA)joinswithribosomal
proteinstomakeribosomes.
3.TransferRNA(tRNA)bindstoanaminoacid
andholdsitinplaceonaribosomeuntilitis
incorporatedintoaproteinduringtranslation

41. Proteins and Cell Regulation
•Thenucleusoverseescells’functionsand
regulatorymechanismsforkeepingthecell
healthyandalive.
•Thenucleuscontrolsgrowthofthecellthrough
thesynthesisofstructuralproteins,energyand
nutrientmetabolism.
•Thenucleusregulatesthesecretionof
ribosomes,whicharemadeinthenucleolus
andarethesitesofgenetranscription.

42. Molecule Movement
•Passive Transport
•Active Transport
•Endocytosis
(phagocytosis & pinocytosis)
•Exocytosis

43. Passive Transport
•No energy required
•Move due to gradient
–differences in concentration, pressure, charge
•Move to equalize gradient
–High moves toward low

44. Types of Passive Transport
1. Diffusion
2. Osmosis
3. Facilitated diffusion

45. Diffusion
•Molecules move to equalize concentration

46. Osmosis
•Special form of diffusion
•Fluid flows from lower solute concentration
•Often involves movement of water
–Into cell
–Out of cell

47. Solution Differences
•Solvent + solute = solution
•Hypotonic
–Solutes in cell more than outside
–Outside solvent will flow into cell
•Isotonic
–Solutes equal inside & out of cell
•Hypertonic
–Solutes greater outside cell
–Fluid will flow out of cell

49. Facilitated Diffusion
•Differentially permeable membrane
•Channels (are specific) help molecule or
ions enter or leave the cell
•Channels usually are transport proteins
(aquaporinsfacilitate the movement of
water)
•No energy is used

50. Process of Facilitated Transport
•Protein binds with molecule
•Shape of protein changes
•Molecule moves across membrane

51. Active Transport
•Molecular movement
•Requires energy (against gradient)
•Example is sodium-potassium pump

52. Endocytosis
•Movement of large material
–Particles
–Organisms
–Large molecules
•Movement is into cells
•Types of endocytosis
–bulk-phase (nonspecific)
–receptor-mediated (specific)

53. Process of Endocytosis
•Plasma membrane surrounds material
•Edges of membrane meet
•Membranes fuse to form vesicle

54. Forms of Endocytosis
•Phagocytosis –cell eating
•Pinocytosis –cell drinking

55. Exocytosis
•Reverse of endocytosis
•Cell discharges
material
•Vesicle moves to cell
surface
•Membrane of vesicle
fuses
•Materials expelled

56. Thank You