Lecture 5-7 Microscopy Flashcards
Number of nanometers in a micrometer
1000
Average size of bacteria
1-2 micrometers (1000-2000 nanometers)
Unit of size for viruses
nanometers
Number of micrometers in a milimeter
1000
Number of lenses a simple microscope has
1
What a light microscope uses to observe things
light
Number of lenses a compound microscope uses
2
Type of light microscope most commonly used in labs
brightfield microscopy
Purpose of ocular lens
the eyepiece; remagnifies image (10x, 20x)
Purpose of objective lens
primary lens that magnifies the specimen (1x - 100x)
Purpose of the stage
holds microscope slide in position
Purpose of condesner
focuses light through specimen
Purpose of diaphragm
controls the amount of light entering condenser
Purpose of illuminator
the light source
Total magnification =
objective lens x ocular lens
Resolution
ability to distinguish between two adjacent objects; very very important
Resolution of compound light microscope
0.2 micrometers
Shorter wavelengths of light =
greater resolution
Refraction
bending of light through different substances
Need immersion oil when
using a magnification above 100x
Purpose of immersion oild
helps capture beam of light and prevents it from bending off
Bright field microscopy is best for
fixed, stained specimens
Dark field microscopy is best for
unstained, live specimens
Phase contrast is best for
unstained, live, and moving specimens
Fluorescence Microscopy
using UV light to visualize locations and patterns, specimen is dead
Confocal Microscopy
using multiple images all put together, gives 3D image
Purpose of contrast
provides a better final image through staining
Dyes
organic compounds that bind to specific cellular materials; usually basic/cationic to bind with negatively charged cell components
3 types of stains
simple, differential, special
Simple stain
use of a single basic dye; used to visualize cell structure and arrangement
Differential stain
separates bacteria into groups
2 types of differential stains
gram and acid fast stains
Purpose of a gram stain
classify bacteria as either Gram-positive or Gram-negative
Bacteria easily killed by antibiotics
Gram-positive
Bacteria more resistant to antibiotics
Gram-negative
Bacteria that appear blue/purple after gram stain
Gram-positive
Bacteria that appear red/pink after gram stain
Gram-negative
Downside of gram staining
kills bacteria cells
Purpose of acid-fast stain
identifies bacteria that have a waxy cell wall (ex. Mycobacteria & Nocardia)
Mycolic acid
waxy lipid material that makes up waxy cell walls
Color of acid-fast stains
red
Purpose of special stains
to stain special structures
Stain for flagella
carbol fuschin
Stain for capsules
colloids
Stain for endospores
malachite green
What electron microscopes use
electron beams
Resolution of an electron microscope (TEM)
0.2 nanometers
2 types of electron microscopes
transmission electron microscope, scanning electron microscopy
Purpose of TEM
images internal structures of cell, need thin slices of the specimen
Purpose of SEM
provides 3D image-surface of cell
Negative staining
stain used in electron microscopy to reveal the texture of the outside of cells, viruses, and isolate sub cellular organelles
Resolution of electron microscope (SEM)
20 nm