Chapter 3 Flashcards
Microorganisms are measured in
micrometers and nanometers
a simple microscope has how many lenses
one
light microscopy
any kind of microscope that uses visible light to observe specimens
types of light microscopy
compound light microscopy, dark field microscopy, phrase contrast microscopy, differential interference contrast microscopy, fluorescence microscopy, confocal microscopy
in a compound microscope the image from the objective lens is magnified again by the
ocular lens
total magnification =
objective lens x ocular lens
10x
low power
40x
high power
100x
oil immersion
resolution (resolving power)
is the ability of the lenses to distinguish two points that are specified distance apart
a microscope with a resolving power of 0.4nm can distinguish between two points at least
0.4nm apart
shorter wavelengths of light provide
greater resolution
refractive index
is a measure of the light bending ability of a medium
once specimen is stained, specimen and medium have different
refractive indexes
increase in magnification and clear image is obtained through
small objective lenses
immersion oil has the same refractive index as
glass
immersion oil is used to keep
light from refracting
in brightfield illumination dark objects are visible against a
bright background
brightfield illumination light is reflected off the specimen
does not enter the objective lens
dark field microscopy light objects are visible against
dark background
dark field microscopy a ________ disk is placed in condenser
opaque
dark field microscopy only light reflected off the specimen enters
objective lens
dark field microscopy is used to look at
live specimen
in dark field microscopy does not need to be
stained
dark field microscopy is also used to look at
specimen not visible in normal microbes
phase contrast microscopy allows examination of
living organisms and internal cell structures
phase contrast microscopy, stain or no stain?
do not need to stain
phase contrast microscopy operation
brings together two sets of light rays, direct rays, and diffracted rays to form an image
differential interference contrast has _____ resolution than phase contrast
better
differential interference contrast microscopy operation
uses two light beams and prisms to split light beams, giving more contrast and color to the specimen
Fluorescence microscopy uses what light
UV light
Fluorescence microscopy operation
fluorescent substances absorb UV light and emit longer wavelength (visible) light
Fluorescence microscopy specimen appear _______ against a dark background
luminous
Fluorescence microscopy is used as a
diagnostic technique
Fluorescence microscopy cells may be stained with fluorescent dyes if they do not naturally
fluoresce
Confocal microscopy is used to make
3D images
Confocal microscopy uses what light to excite a single plane of a specimen
short wavelength (blue)
two photon microscopy can track the
activity of cells
two photon microscopy uses what dye
fluorchrome
two photon microscopy operation
two photons of long wavelength (red) light are used to excite the dyes
super resolution light microscopy uses two
laser beams
the two laser beams in super resolution light microscopy are used to
one beam stimulates fluorescent molecules to glow
second beam cancels out all fluorescence except for that in one nm
super resolution light microscopy can use different dyes for different molecules meaning
this type of viewing can allow for a single molecule to be tracked
scanning acoustic microscopy (SAM) us used to look at cells that are
attached to a surface
scanning acoustic microscopy used
sound waves
electron microscopy uses _______ instead of light
electrons
2 types of electron microscopy
scanning and transmission
electron microscopy the shorter the wavelength of electrons gives the
greater the resolution
electron microscopy can look at
viruses
transmission electron microscopy operation
a beam of electrons passes through ultra thin sections of a specimen then through an electromagnetic lens, then focuses on a projector lens
transmission electron microscopy stains
heavy metal salts
transmission electron microscopy specimens are placed on
copper mesh grid
transmission electron microscopy disadvantages
- only very thin section of specimen can be studied
- no 3D
- specimens have to be fixed, dehydrated, and viewed under a high vacuum to prevent electron scattering
prep of a specimen may cause shrinkage and distortion this is known as
artifacts
scanning electron microscopy (SEM) operation
an electron gun produces a beam of electrons that scan the surface of the entire specimen
scanning electron microscopy can produce what type of image
3D
2 types of scanned probe microscopes
scanning tunneling microscope and atomic force microscope
scanning tunneling microscope uses a
Tungsten probe to scan a specimen and reveal details of its surface
scanning tunneling microscope is used to see
DNA
scanning tunneling microscope does not require any
prep
atomic force microscopy operation
uses a metal and diamond probe placed onto specimen movements are recorded
atomic force microscope produces what image
3D
atomic force microscope is used to see what
biological substances and micro logical processes
atomic force microscope does not require
prep
