Transcript Microscopes - Northern Highlands Regional HS / Overview
CP BIO: Microscopes
Use light or electrons to magnify Enable us to see the shape and structure of very small objects
Magnification
Total magnification = ocular lens X objective lens
Real size Magnified 400 X
Elodea canadensis Cell walls cytoplasm
Pond weed
chloroplasts central vacuole
How two lenses magnifies
Resolution or Resolving Power
Resolution
= sharpness, clarity of focused image • “Ability to show two close points as separate” • Depends on shape and perfection of lenses • A light microscope can show objects as small as 1 m high resolution lens lower resolution lens
Depth of Field • Thickness of layer in focus • Higher magnification
thinner
layer
Light Microscopes (LM) • Light passes through a thin specimen • Use lenses to focus light – Simple microscope – one lens – Compound microscope – two lenses • Magnifies image
twice
Leeuwenhoek’s Microscope • Anton von Leeuwenhoek, 1600s • First powerful scope with high resolution – Single lens – Magnify ~ 300 X
Leeuwenhoek’s microscope
Advantages of light microscopes Can magnify up to 2000 times Shows shape and structure of cells and tiny organisms Specimens can be alive Disadvantages Specimens must be thin enough for light to pass through Image appears inverted and backwards Often need stain to see better (stain kills cells)
Cheek cells with stain Common stains: methylene blue, Lugol’s iodine “Vital stains” - stain without killing cells
Phase-Contrast Microscope Increases contrast without staining good for living organisms Cheek cells without stain 11
Compound Microscope
cheek cells – stained
Phase-Contrast
cheek cells –unstained
nucleus cytoplasm cell membrane nucleus cytoplasm cell membrane
Amoeba, one-celled organism preserved, stained alive, moving
Compound scope Phase-Contrast scope
Cell cycle, under phase contrast 14
Stereomicroscopy “Dissecting microscope” Has ocular lens and objective lens for each eye stereoscopic vision, 3-D Image NOT inverted Magnifies 10-50X 15
Advantages of stereoscopes • Image NOT inverted or backwards • Makes manipulation easy • Specimens can be solid, living • Disadvantage: magnifies up to ~50 X
Stereomicroscope – whole specimens chick embryo soil worm 17
Electron Microscope Uses electrons instead of light Magnets focus the electron beam Image on monitor 18
Electron Microscope • Invented 1930s • Very high magnification and resolution • Show cell details – internal anatomy, “ultrastructure”
Advantages of electron microscopy • Electron are much smaller than the wavelength of light – show things that light cannot show • Very high magnification – up to 500,000X • Very high resolution - up to 1 nanometer • DISADVANTAGE – specimen must be dead, dried, coated, in vacuum chamber
Scanning Electron Microscope SEM • Electron beam skims across specimen surface • Shows tiny surface details • Magnifies up to 50,000 times • DISADVANTAGE: shows surface, but not interior
Compare LM and SEM Blood cells (LM) Blood cells (SEM)
SEM micrographs
Euglena (protist) SEM Ant head, SEM
Scanning Electron Microscope (SEM) shows surface details Electrons
scan
across surface of specimen 24
SEM of DNA Image made with special scanning “tunneling” microscope 25
Transmission Electron Microscope (TEM) shows
inside
cells • Electrons pass
through
thin specimen • Shows great detail of internal structure • Magnifies up to 500,000 times!!
Rough ER Mitochondria Nucleus
Comparing microscopes
Euglena
LM
Euglena
SEM
Euglena
TEM
Transmission Electron Microscope
Bacterium dividing Muscle fibers Phage virus Cilia and basal bodies Liver cells Chloroplast
28
Comparing microscopes
Euglena, LM Euglena, SEM Euglena, TEM
29
Which type of microscope produced these micrographs?
Amoeba
, preserved and stained
Amoeba
, alive and unstained Vacuole inside a cell 30
Which type of microscope made these micrographs?
Female and male fruit fly
Closterium -
Unicellular green alga 31
Name the microscope Leaf cross-section 400X chloroplast 5,000 X
Name the microscope Eye of a housefly Iridescent beetle 33
Which microscope?
34
Fluorescent Microscopy • Uses lasers on thin slices;
confocal
scope • Fluorescent dyes show different molecules
Cancer cells tagged with 3 fluorescent dyes shows cell microtubules (blue), microfilaments (yellow), DNA (green)
Confocal Microscopy
Specialized Cells in the Ear
E. Coli
bacteria