Ch. 2 Connect Assignment

The student forgot to add the counter stain

A fellow student carries out the Gram stain on a mixed culture containing Gram-negative rods and Gram-positive cocci. On completion he finds purple cocci and clear (no color) rods when viewing the prepared slide with a microscope. From the following, choose the best reason for these results.

bright-field

A/An ________ microscope uses lenses made of glass to focus light onto a specimen.

Pink Gram-positive and pink Gram-negative cells

After performing a Gram stain of a mixed culture of Gram-positive and Gram-negative cells, you realize you forgot to apply the iodine in step 2. What would you expect to see if you observed the slide under the microscope after this omission?

objective lens, real image

An _______ ______ gathers light from a specimen and focuses it to produce a _____ ________.

Lens A: 1.3 mm

Approximate focal lengths for four different objective lens are given below. Choose the lens that would provide the highest magnification: 1.3mm 40mm 4mm 17mm

heat; chemicals

Bacteria and archaea are typically fixed to slides by ________ while eukaryotes with subcellular structure, such as protists, are typically fixed by _________.

eukaryotes and archaeon

Chemical fixation is often used for ________, particularly with the use of electron microscopes, whereas heat fixation is typically used when observing bacteria and _________ with a light microscope, since it is easy and adequate.

fixation, staining

During the _______ process, cells are killed and adhered firmly to the slide so they do not wash off during the _______ process.

confocal

Laser light is used in ____________ microscopy, generating three-dimensional images.

nosepiece

Objective lenses are contained in a ___________ that can be turned to put a particular objective lens in place to be used.

stage

Slides containing specimens are mounted on the _____ of the microscope.

true

T/F Acetone can be used as the decolorizer in the Gram stain procedure.

false

T/F Bacteria and archaea are typically fixed to slides by chemicals.

False

T/F The Gram stain can only be performed on cultures grown in liquid media.

False

T/F The focal length for a low power objective lens would be shorter than that for an oil immersion lens.

cell wall

The Gram stain of a bacterial cell is based on the chemical properties of its ________.

ocular lens, virtual image

The _______ _____ magnifies an image produced by the objective lens to produce a ______ ______

crystal violet, iodine, ethanol, safranin

The proper sequence of reagents in the Gram stain procedure is _________.

iris diaphragm

The___ ________ is a type of shutter found under the stage of many microscopes that can be used to adjust the light intensity on the specimen.

heat, morphology, and chemical

There are two main methods for fixing cells to a slide; heat fixation and chemical fixation. _______ fixation is valuable in that it preserves the overall ___________ of the specimen; however, it also distorts internal structures. ________ fixation preserves the integrity of the cellular substructures as well as the morphology.

slows, greater

When light generated by a lamp in a light microscope passes into a lens, the speed of the light _______ because the glass lens has a _______ refractive index than the air from which the light came.

differential interference contrast

When polarized light is needed for imaging a ____________ microscope is used.

microscopic

When preparing specimens for ______ observation, it is important to preserve the internal and external structures so they resemble living cells as much as possible.

fluorescence microscope

Which of the following microscopes typically uses dyes or antibodies?

gram-stain

Which of the following stains would best determine if a bacterium has a single cell membrane plus a very thick cell wall or if a bacterium has a very thin cell wall in between two cell membranes?

short

a lens with a _____ focal length should have a greater magnification

contrast

ability to be distinguished from the surroundings

dark-field

in _____ _______ microscopy, however, bright images on a darker background are produced because only light that is refracted by the specimen is captured.

epifluorescence

light at specific wavelengths is used to excite dyes in specimens that then emit light at specific wavelengths in ____________ microscopy

oil immersion, high power, low power

order the objective lenses listed from the smallest to largest working distance that results when they are used.

phase contrast

the _____ _____ microscope uses slight differences in refractive indices and an annular condenser to produce sharper images than simple bright fields.

resolution

the ability to distinguish between two separate structures that are very close to one another

magnification

the apparent increase in size of an image

bright-field microscope

the most commonly used type of microscopy is ______ ______ because the specimens produce dark images against brighter backgrounds

scanning electron

what microscope would be the best to use to view cell surface features of a specimen?

transmission electron microscopy

what would be the best technique to prepare and view the internal structures of fungal hyphae?