LESSON 5 ELECTRON MICROSCOPY TYPES OF MICROSCOPY Light

LESSON 5 ELECTRON MICROSCOPY

TYPES OF MICROSCOPY � Light Microscopy � � � � Bright-field microscopy Phase Contrast microscopy Differential Interference Contrast (or Nomarski) Dark-field microscopy Fluorescence microscopy Confocal Scanning microscopy Electron Microscopy � � Transmission electron microscope (TEM) Scanning electron microscope (SEM)

Learning Resources 1. Junqueira’s Basic Histology ; pp 7 & 9 2. Looking at the Structure of Cells in the Microscope http: //www. ncbi. nlm. nih. gov/books/NBK 26880/#A 1749 ▪ The Electron Microscope Resolves the Fine Structure of the Cell. ▪ Images of Surfaces Can Be Obtained by Scanning Electron Microscopy ▪ Metal Shadowing Allows Surface Features to Be Examined at High Resolution by Transmission Electron Microscopy ▪ Freeze-Fracture and Freeze-Etch Electron Microscopy Provide Views of Surfaces Inside the Cell

Resolution, resolution!!!

Electron Microscopy Why electron beams? R = 0. 61λ/ N. A. The wavelength, much shorter than of light Types Transmission electron microscope (TEM) Scanning electron microscope (SEM) - surface contours TEM SEM

Electromagnetic lenses • a coil of wire through which current flows • magnetic field in the center. • electrons traveling in their path down the central hole.

TEM

Contrast in TEM Dark (Electron dense) (Electron transparent) Bright (Electron lucent)

• Bright (Electron lucent) - electrons readily passed • Dark (Electron dense) - electrons absorbed

Transmission electron microscope (TEM)

SEM DIC TEM

SEM

Scanning electron microscope (SEM)

Metal Shadowing • high resolution three-dimensional replica of the specimen • heavy metal shadowing of bacteria to demonstrate flagella

Freezing Techniques • Freeze-Fracture • Freeze-Etch

TEM Section and Freeze Fracture