1. Chapter 4: Microscopy and Cell Structure
Resolution
Limits to Resolving Power:
Refractive Index
Aberration: Early lenses were generally not homogenous glass
and had variable refractive index across their surface, leading to
distortion

3. Types of Microscopes Brightfield Phase Contrast
Differential Interference Contrast (DIC or Namarski)
Darkfield
Fluorescence
Con-Focal
Transmission EM
Scanning EM
Atomic Force Microscopy (AFM)
Light
Electron

4. Principal of DIC (Differential Interference Contrast) OR
Phase Contrast microscopy
Highligts:
Edges & Surfaces of objects

5. Fluorescence Microscope Optic Train

6. Microscope Comparison (Lens Trains)

7. TEM vs. SEM TEM SEM can go to very high resolution
see internal structure
can go to very high resolution
--- down to about 5 nm directly (further with image
averaging technique)
--- down to about 0.2 nm (2 angstrom) with electron
crystallography
cannot see surface features separately
see entire thickness of sample
SEM
see surface features only
can do elemental analysis of scattered electrons
lower resolution than TEM (around nm)
sample preparation more difficult (but generally fewer artifacts)

8. Atomic Force Microscopy (AFM)
Advantages:
Range of resolutions
Live specimens
Cost
Disadvantages:
Image quality
Time consuming
ml2e-fig jpg

9. Prokaryotic Cell Structure
Cell Shape
Rod/Bacillus
Bent Rod/ Vibrio
Spirillum (rigid helical shaped cell)
Spirochete (flexible spiral cell, contains a flagellum between
the cytoplamic membrane and outer membrane)
“Multicellular” Prokaryotes
actinobacteria form extensive networks of filaments that are
all cytoplamically contiguous (although there is some
barrier to free movement of material)
filamentous cyanobacteria also form filaments, in some
cases with cellular specialization
Also keep in mind that most bacteria live in communities

10. Cell Division Internal Structures Fission (generally symmetrical)
Budding (distinctly asymmetrical)
Fragmentation
Internal Structures
DNA
Bacterial Chromosome (one DS molecule, haploid)
Plasmids (replicate independently of chromosome)
Transformation
Conjugation
Transduction
Ribosomes (60 S) rRNA & Protein, involved in translation
Linked transcription & translation common in prokaryotes
Gas vesicles
Surrounded by protein sheath, used for buoyancy
Storage particles (Store nutrients and essential elements)
Glycogen/ Starch
Poly-B-hydroxybutryic acid (PHB)
Horizontal
Transfer