What could have been the most precisely resolved object seen under a Leeuwenhoek microscope?
a red blood cell
Why do most microbes have poor contrast?
they are colorless
Oil immersion lenses help microscopists increase
magnification and resolution
For a light microscope, the limit of resolution is determined by
the wavelength of visible light
Living microbes can best be viewed using which type of microscopy?
The resolving limit of the best light microscope under the best of contidtions is __________, whereas that of a scanning electron microscope is ______________.
200 nm, 10nm
What is the major difference between SEM and TEM?
SEM produces a 3D image
If you were performing a Gram stain on a bacterial sample and forgot the step that uses ethanol and acetone, what color would the cells be at the end of the Gram staining procedure?
The most appropriate stain to use to indentify a bacterial species that produces thick, waxy cell walls is the
In staining, the purpose of a mordant is to
bind dyes to make them less soluble
The major difference between the stains used in electron microscopy and those used in light microscopy is that stains for the electron microscope are
heavy metals and electron dense
The goal of modern classification schemes has shifted from a simple desire to catalog organisms to a desire to
understand phylogenetic relationships
determine common acestors
determine evolutionary relationships
In the domain system of nomenclature, differences between organisms are based on
Why are viruses NOT included among the three domains or five kingdoms of modern taxonomy?
a.they are acellular
b.too small to be readily studied
c. they were not included in older taxonomic systems so should not be included in new systems
d. none of the above apply to viruses
d. none of the above apply to viruses
Empty magnification produces images that are faint and blurry because the image lacks sufficient_________ and ______.
Fluorescent microscopes have __________ (better/worse) resolution than standard bright-field microscopes because UV light has a __________ (longer/shorter) wavelength than visible light.
The two types of microscopy that produce direct 3D images for viewing are _________ and __________.
differential interference, scanning electron
Electron microscopy is most useful for viewing a cell's ________________, those parts of the cell that can't be seen any other way.
Staining is useful because it increases ____________ between structures or a specimen and its background; this, in turn, allows for better ____________.
Anionic chromophores are called _________ dyes and bind to ___________ (acidic/basic) structures, whereas cationic chromophores are called __________ dyes and bind to (acidic/basic) structures
Acidic, basic, basic, acidic
In order for cells exposed to a negative stain to be stained themselves, a ___________ must be added, otherwise the cells remain colorless.
Taxonomy consists of three parameter: ___________, __________, and _________.
Classification, nomenclature, identification
In _________ tests, antiserum is mixed with patient samples. Antiserum contains __________ that recognize microbial __________.
agglutination, antibodies, antigens
Refers to the use of light or electrons to magnify objects
distance between two corresponding parts of a wave
apparent increase in size of an object and is indicated by a number followed by an "x"
the ability to distinguish objects that are close together; also called resolving power
lenses ability to gather light
used to fill the space between the specimen and a lens to reduce light refraction and thus increase the numerical aperture and resolution
most common type of microscope; prevents light from directly entering the objective lense
two types of bright-field microscopes
simple microscope - single lens; similar to a magnifying glass
compound microscope - uses a series of lenses
parts of a compound microscope
revolving nosepiece - where objective lenses are mounted
ocular lenses - lenses closes to the eyes
condenser lenses - lie beneath the stage of the microscope and direct light through the slide
photograph of a microscopic image
microscope that utilizes a dark field stop in the condenser that prevents light from directly entering the objective lens; pale objects are best observed with this microscope
uses fluorescent dyes in conjunction with UV lasers to illuminate the fluorescent chemicals in only a single plane of a specimen at at time
generates a beam of electrons that passes through a thinly sliced, dehydrated specimen, through magnetic fields that changes the electrons energy into visible light
TEM (transmission electron microscope)
thing film of organisms on a slide
passing a slide through a flame
applying a chemical to a slide
colored portion of a dye
composed of a single basic dye such as crystal violet and involve no more than soaking the smear in the dye and rinsing
use more than one dye so that different cells, chemical,s or structures can be distinguished