Lecture 4 Flashcards
What are the two types of microscopes?
Light microscope - compound light
Electron microscope - transmission/ scanning/ electron microscope and scanning tunneling microscopy
What are the characteristics of light microscopes?
Uses two lenses: objective lens (10x - 100x) and ocular lens (in eye piece 10x)
Uses light to see specimens
What is resolution?
The ability to distinguish detail and structure (2 points at a certain distance apart)
Light must pass in between two points to be seen clearly therefore wavelength must be short (shorter wavelength = better resolution)
What are electron microscopes?
Use beams of electrons instead of light
Electrons travel in smaller wavelengths
Able to magnify 500,000x
Can see inside cell structures and viruses
What are the resolution differences between light and electron microscope?
Human eye - 0.10mm
Compound microscope - 0.20 um
Electron microscope - 0.20 nm (better resolution)
What are the characteristics of a transmission electron microscope?
Used to see internal cell structures
Cannot penetrate thick cell therefore must be cut first - thin sectioning and stained
Uranium stain to increase contrast
What are the characteristics of scanning electron microscopes?
Only view surface of object
Must be coated with thin film of heavy metal
15x - 100,000x
What are the characteristics of scanning tunneling microscopy?
Most powerful
Visualize atoms
Use thin metal probe to scan and reveal surface irregularities, bumps, depressions
What is a chromophore?
Stained microorganisms
What are the 2 ways to use stains?
Positive stain - Outer surface of bacteria carry a negative charge and will attract positive stain
Negative stain - negatively charged bacteria will repel negative stain and be colourless while the background will be coloured
What are the 2 staining techniques?
Simple stain - no specific stain. A single colored basic dye is used to see negative charged bacteria
Differential stain - used to see two different types of bacteria (gram stain/ acid fast stain)
Differential stain: Gram stain vs acid fast stain
To see if bacteria is gram positive or gram negative
Red stain will bind to acid fast waxy cell wall bacteria
Counter stain methylene blue will leave tissue and non acid fast bacteria blue
Special stains: capsule stain vs. Endospore stain vs. Flagella stain
Capsule - shows thick polysaccharide layer outside bacteria. Capsules means increased ability to cause disease. Negative stain to see background and positive stain to see cell while capsules does not take up colour
So see if spore is awake (pink) or asleep (green).
