honors biology microscopes

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Honors Biology Microscopes. Important tool for all biologists. Honors Bio: Microscopes. Use light or electrons to magnify Enable us to see the shape and structure of very small objects Cells and cell parts Tissues Molecules (only with electron microscopes) - PowerPoint PPT Presentation



Honors BiologyMicroscopesImportant tool for all biologistsHonors Bio: MicroscopesUse light or electrons to magnify Enable us to see the shape and structure of very small objects Cells and cell partsTissuesMolecules (only with electron microscopes)Small and microscopic organismsValue of Magnification

Real size Magnified 400 X

Elodea canadensisPond weed cytoplasmcentral vacuole Cell wallschloroplasts

MagnificationMagnification = object size ~ image size

Euglena, a one-celled organism 1000Xchloroplastsflagellumfood vacuolenucleus Total magnification = ocular lens X objective lensResolution or Resolving PowerAbility to show two close points as separate Depends on shape and perfection of lensesHuman eye can see objects as small as 0.2 mmA light microscope can resolve objects as small as 0.2 m

high resolution lens lower resolution lens Resolution = sharpness, clarity of focused imageComparing ResolutionsOptical InstrumentResolving PowerRP in Angstroms

Human eye0.2 millimeters (mm) 2,000,000 ALight microscope0.20 micrometers (m)2000 AScanning electron microscope (SEM)5-10 nanometers (nm)50-100 A(TEM) Transmission electron microscope0.5 nanometers (nm)5 ADepth of FieldThickness or layer in focus

Higher magnification thinner layer

Light Microscopes Send LIGHT through a thin specimen

binocular light microscope8an early microscope

Light Microscopes (LM)Light waves pass through a thin specimenLenses bend light to magnify imageSimple microscope one lensCompound microscope two lensesMagnifies image twice

Leeuwenhoeks MicroscopeAnton von Leeuwenhoek, 1600sFirst powerful scope with high resolutionSingle lensMagnify ~ 300 XLeeuwenhoeks microscope

LE 4-1aEyepieceOcularlensObjective lensSpecimenCondenserlensLightsourceBINOCULAR MICROSCOPE has ocular lens for each eyeHow two lenses magnifies

Leaf cross-section (LM)Epithelial cell

Photosynthetic cells

Chloroplast (dots inside cell)

Stoma (leaf opening)Advantages of light microscopesCan magnify up to 2000 timesShows shape and structure of cells and tiny organismsSpecimens can be aliveSpecimens must be thin enough for light to pass throughImage appears inverted and backwardsOften need stain to see imageDisadvantagesCheek cells with stain

Common stains: methylene blue, Lugols iodine

Vital stains - stain without killing cells Light microscope LM dark fieldPhase-Contrast MicroscopeDifferential Interference Microscope

Increases contrast between tissue densities dont need stain; good for living organisms17Cheek cells without stain

Compound Microscope cheek cells stained nucleuscytoplasmcell membrane Phase-Contrast Microscope cheek cells unstained nucleuscytoplasmcell membrane18

Amoeba, one-celled organism preserved, stained alive, movingCompound scope Phase-Contrast scopeCell cycle, under phase contrast


Phase-contrast micrograph of a roundworm 630X

Has ocular lens and objective lens for each eye Stereoscopic vision, 3-DImage NOT invertedMagnifies 10-50X22StereomicroscopeDissecting microscopeAdvantages of stereoscopesImage NOT inverted or backwardsMakes manipulation easySpecimens can be solid, living

Disadvantage: magnifies up to ~50 X

Stereomicroscope whole specimens chick embryo soil worm

24Fluorescent MicroscopyUses lasers on thin slices; confocal scopeFluorescent dyes show different molecules

Cancer cells tagged with 3 fluorescent dyes shows cell microtubules (blue), microfilaments (yellow), DNA (green)Fluorescent shows different cell parts as different colorsDetails in a single layer

Fruit fly embryo developmental layersGreen microtubules in cytoplasm Red -DNAhttp://www.microscopyu.com/tutorials/java/virtual/confocal/index.html

Confocal Microscopy E. Coli bacteria

Specialized Cells in the Ear Electron Microscope

Uses electrons instead of lightMagnets focus the beamImage shows on monitorMagnify up to 1 million timesShow cell details, interior- ultrastructureInvented 1930sNobel for Ruska 198628Electron MicroscopeHow does it work?Specimen is coated with a metal filmElectron beam hits metal, ejects electrons from metal atomsThese electrons make the image

Advantages of electron microscopyElectron are much smaller than the wavelength of light show things that light cannot showVery high magnification up to 1,000,000X Very high resolution - up to 1 nanometer

DISADVANTAGE specimen must be dead, dried, coated, in vacuum chamber

Scanning Electron MicroscopeSEMElectron beam skims across specimen surfaceShows tiny surface structures in great detailMagnifies up to 50,000 times

DISADVANTAGE: shows surface, but not interiorCompare LM and SEM

Blood cells (LM) Blood cells (SEM)SEM micrographs

Euglena (protist) SEM

Ant head, SEM

Scanning Electron Microscope (SEM) shows surface detailsElectrons scan across surface of specimen 34


35Image made with special scanning tunneling microscope Transmission Electron Microscope (TEM) shows inside cells

Electrons pass through thin specimenShows great detail of internal structureMagnifies up to 1,000,000 times!!Rough ERNucleusMitochondriaTransmission Electron Microscope

37Phage virusBacterium dividingMuscle fibersCilia and basal bodiesLiver cellsChloroplast

Comparing microscopes

Euglena LMEuglena SEMEuglena TEMWhich type of microscope produced these micrographs?

Amoeba, preserved and stainedVacuole inside a cell39

Amoeba, alive and unstainedWhich type of microscope made these micrographs?

Female and male fruit fly Closterium -Unicellular green alga40Name the microscope

Leaf cross-section 400X chloroplast 5,000 XName the microscope

Eye of a houseflyIridescent beetle

42Which microscope?