operate the compound light microscope - studentvip
TRANSCRIPT
TheMicroscope
Operatethecompoundlightmicroscope
MicroscopeTheory
• Magnificationistheenlargementofanimage• Theminimumresolveddistanceistheminimumdistanceatwhichtwoobjectsorimagescanbe
identifiedasdistinctfromeachother• Thesystemoflensesinthecondensercontrolsthefocusofthelightbymovingupanddown• Whentheconeoflightjustfillsthelensoftheobjective,maximumresolvingpowerisobtained• Theamountoflightreachingtheobjectiveiscontrolledbytheirisdiaphragm• Whentheangularapertureofthecondenseririsdiaphragmistoonarrow,thefieldofviewwillbetoo
dark,theresolutionpoor,andthecontrasttoohigh• Thecontrolonthelightsourcecontrolstheintensityofthelight• Theimageseenthroughtheeyepieceisinvertedandmagnified
Applyascaletoyourdrawings• Ascaleisusedsotherepresentationcanberelatedtothesizeofthespecimenratherthana
magnificationasitdistortsthephoto
Estimatethesizeofmicroscopicobjects• Whenthediameterofthefieldofviewofanobjectivelensisknown,theapproximatesizeofanobject
viewedonaslidecanbedeterminedbyestimatingthenumberoftimestheobjectfitsacrossthediameterofthefieldofview
1.CellStructure
Describethestructuresandfunctionsofa(eukaryotic–membrane-bound)animalcellOrganelle FunctionNucleus Directscell’slifeprocesses,containsthechromosomesandDNA
Nuclearmembrane Separatesthenucleusfromthecytoplasm.Controlsthehighly-selectivetwo-wayexchangebetweenthenucleusandcytoplasm(vianuclearpores)
Nucleolus DenseareainthenucleuswhichcontainsgenesthatsynthesiseribosomalRNAwhichiscombinedwithproteins
Cytoplasm(cytosol) Semi-fluidmaterialinwhichtheorganellesarefoundCellmembrane(plasmamembrane)
Regulatesmovementofsubstancesintoandoutofthecell(Alsoreferredtoasphospholipidbilayer)Centre:hydrophobic‘waterhating’Outside:hydrophilic‘waterloving’
ProteinchannelsPassive–allowsmovementacrossagradient,hightolowconc.Active–requiresenergytomoveionsacrossthemembrane
Mitochondria
Cellularrespiration(producesATP–energy)
Roughendoplasmicreticulum
Siteofproteinsynthesisandtransport(representedbydotsonsurfacewhichrepresentribosomes)
Smoothendoplasmicreticulum
Siteoflipidsynthesis,proteinmodificationanddetoxifyingpoisons(inliver)
Golgibody Storage,modificationandpackagingofproteins(carbohydrates,lipids,hormones,channelproteins)Secretoryproteinsremovedbyexocytosis
Lysosome(formedbygolgi)
ContainshydrolyticenzymesforcellulardigestionandcelldefenceBreaksdownbacteriabyendocytosis(engulfing)
Ribosome ProteinsynthesisCytoskeleton Microtubules–formtheshapeofthecell(centrioles,ciliaandflagella)
Intermediatefilaments–givestrengthtocell(actin,myosin)Microfilaments–allowabsorptionofnutrients,max.SA(microvilli)
3.Muscles
Describethethreemainmuscletissuetypes SkeletalMuscle CardiacMuscle SmoothMuscleLocation Attachedtobones Intheheart Inthewallsofholloworgans,
bloodvessels,eyes,glands,skinCellshape Verylong,cylindricalcells Cylindricalcellsthatbranch Spindle-shapedcellsNucleus Multinucleated,peripherally
locatedSingle,centrallylocated Single,centrallylocated
Striations Yes Yes NoControl Voluntary(conscious) Involuntary(unconscious) Involuntary(unconscious)Abilitytocontractspontaneously
No Yes Yes
Function Movesthebody Providesthemajorforceformovingbloodthroughthebloodvessels
Movesfoodthroughoutdigestivetract,emptiestheurinarybladder,regulatesbloodvesseldiameter,changespupilsize,contractsmanyglandducts
Specialfeatures
None Branchingfibres,intercalateddiskscontaininggapjunctionsjoiningcellstoeachother
Gapjunctions
StatetheslidingfilamenttheoryofmusclecontractionandexplaintheroleofcalciuminmusclecontractionStriatedmuscle
• Movementofboneso Flexionandextension
• Containslotsofnervesandbloodvesselso Reservoirforblood
• Slidingfilamenttheoryo Thickfilamentsaremadeofmyosino Thinfilamentsmadeofactino Sarcomere–themuscleunitthatdoes
theworko Whenthemusclesarerelaxedthe
actinisseparatedattheH-zoneandpulledtogetherwhenmuscleistensed
Neuro-muscularjunction
• Sarcoplasmicreticulumisendoplasmicreticulumforskeletalmuscleo Holdsthecalcium(insolution)
• Nervecellsbringthenervestothemuscle• Neurotransmittersreleasemusclereceptorstoopenupandallowpositivechargestorushintothe
muscle(de-polarisation)o De-polarisation–rapidinfluxofpositivecharges
• Ttubulestransmitschargesallthroughmuscletissuewhichcausessarcoplasmicreticulumtoreleasecalciumwhichcausesmusclecontractions
• Musclemolecules:o Myosin–pullsactin
§ Stemcanbendtograbtheactin§ ATPturnsintoADPfirst§ Gamma-phosphateattachestomyosinandpullthe
myosinheadback,whenthegamma-phosphateisreleased,theheadspringsbackintotheshape,pullingtheactinfilaments
o Actin–doublehelixstructure,blackdotsarebindingsiteformyosinhead
o Tropomyosin–stopsmusclesfromcontractingconstantly§ Wrapsaroundactinbindingsitesandobstructsmyosinbinding
o Troponin–switchthatpullsthetropomyosinawayfromthebindingsite
o Calciumions–triggersthetroponinbybindingtoitandcausingittochangeshape§ Calciumcomesfromtheterminalcisternae
inthesarcoplasmicreticulumo ATP–gamma-phosphateaddedontomyosin
§ Gammacomesoffandputsachargeonmyosinwhichdisruptstheinteractionbetweenaminoacidsthuschangingtheshapeoftheprotein
§ Composedof:ribose-sugar,adenine,phosphateswithnegativelychargedphosphatesattached(alpha,beta,gamma)