Micro mod 2

Cards (71)

  • Microorganisms are too small to be seen with the unaided eye and must be observed with a microscope
  • The word microscope comes from the Latin word "micro" (small) and the Greek word "skopos" (to look at)
  • Modern microbiologists use microscopes that produce magnifications ranging from ten to thousands of times greater than van Leeuwenhoek's single lens microscope
  • Helicobacter pylori is a spiral-shaped bacterium first seen in cadaver stomachs in 1886
  • Some microbes are more readily visible than others due to their size or observable features
  • Microorganisms must undergo staining procedures before their cell walls, capsules, and other structures lose their colorless natural state
  • Microorganisms and their components are measured in micrometers and nanometers
  • A micrometer (μm) is equal to 0.000001 m (10^-6 m) and a nanometer (nm) is equal to 0.000000001 m (10^-9 m)
  • Light microscopy uses visible light to observe specimens
  • A compound light microscope has a series of lenses and uses visible light for illumination
  • Total magnification of a specimen is calculated by multiplying the objective lens magnification by the ocular lens magnification
  • Resolution in microscopy refers to the ability of lenses to distinguish fine detail and structures
  • The resolving power of a microscope is influenced by the wavelength of light used
  • To achieve high magnification with good resolution, immersion oil is used with the objective lens
  • Darkfield microscopy is used to examine live microorganisms that are invisible in ordinary light microscopes or cannot be stained
  • Phase-contrast microscopy allows detailed examination of internal structures in living microorganisms without the need for fixing or staining
  • Differential interference contrast (DIC) microscopy uses differences in refractive indexes and two beams of light to produce brightly colored, nearly three-dimensional images
  • Fluorescence microscopy takes advantage of substances that absorb short wavelengths of light and emit light at longer wavelengths
  • Confocal microscopy is used to reconstruct three-dimensional images by illuminating one plane of a specimen at a time
  • Two-photon microscopy (TPM) uses long-wavelength light and requires two photons to excite the fluorochrome to emit light
  • Scanning acoustic microscopy (SAM) interprets the action of a sound wave sent through a specimen to study living cells attached to surfaces
  • Electron microscopy is used to examine objects smaller than about 0.2 μm, such as viruses or internal cell structures
  • In electron microscopy, a beam of electr
  • Electron microscopy is used to examine objects smaller than about 0.2 μm, such as viruses or the internal structures of cells
  • In electron microscopy, a beam of electrons is used instead of light
  • The resolving power of the electron microscope is far greater than that of other microscopes due to the shorter wavelengths of electrons
  • Electron microscopes are used to examine structures too small to be resolved with light microscopes
  • Images produced by electron microscopes are always black and white, but they may be colored artificially to accentuate certain details
  • Electron microscopes use electromagnetic lenses to focus a beam of electrons onto a specimen
  • There are two types of electron microscopes: transmission electron microscope (TEM) and scanning electron microscope (SEM)
  • Transmission Electron Microscopy (TEM)
  • In TEM, a beam of electrons passes through a specially prepared, ultrathin section of the specimen
  • The beam is focused on a small area of the specimen by an electromagnetic condenser lens
  • Scanning Electron Microscopy (SEM)
  • SEM provides three-dimensional views of specimens
  • In SEM, an electron gun produces a finely focused beam of electrons called the primary electron beam
  • The primary electron beam knocks electrons out of the surface of the specimen, and the secondary electrons produced are used to produce an image called a scanning electron micrograph
  • Scanned-Probe Microscopy
  • Scanned-probe microscopes use probes to examine the surface of a specimen using electric current
  • Scanned-probe microscopes can be used to map atomic and molecular shapes, characterize magnetic and chemical properties, and determine temperature variations inside cells