Lab Midterm (labs 1-7) Flashcards
Define transmission electron microscopy (TEM)
Electrons pass through the cell, so you can see detailed images of its inside
Define scanning electron microscopy (SEM)
Electrons bounce off the cell, so you can capture detailed images of its surface
Define ocular lens
Binocular lenses to which you place your eyes for viewing the specimen. These lenses have a set magnification of 10x
Define objective lenses
Three or four lenses mounted on a turret that provide the major magnification power of the microscope. These lenses are rotated into place immediately above the specimen. Typical magnification powers usually include 4x, 10x, 40x, and 100x. In concert with the ocular lenses, these objective lenses yield total magnification powers of 40x, 100x, 400x, and 1000x
Define revolving turret
A mechanism allowing movement of the different objectives into place above the specimen
Define stage
Flat plate on which the specimen is placed. Light passes from the condenser through a hole in the plate and then through the specimen on a microscope slide.
Define slide clamp
Holds the glass slide with the specimen in the correct place for observation, allowing the entire slide to be moved by the slide manipulator
Define slide manipulator
Through the use of a system of gears, the manipulator moves the slide clamp holding the slide. This allows for smooth movement of the slide, allowing precise location of different parts of the slide
Define condenser
A series of lenses that focuses light traveling from the light source on the specimen. Depending on the type of microscope, condensers can provide multiple settings. Settings often seen include bright field (used most often), dark field (providing excellent illumination of the edges), phase contrast (enhancing poorly contrasting objects), and many other options
Define iris diaphragm
Allows for the reduction of or expansion of the amount of light passing from the condenser to the specimen
Define coarse focus adjuster
Allows for focusing the image on lower power objective lenses (4x or 10x lenses). Often used to quickly scan specimens and focus in on interesting items on the slide
Define fine focus adjuster
Allows for focusing the image on higher power objective lenses (40x or 100x lenses). Since the working distance of these higher power lenses is relatively small, the fine focus is the only focus that should be used with these; use of coarse focus on the higher power lenses could lead to lens damage
Define rheostat
Power control that increases or decreases the voltage applied to the light source, increasing or decreasing the brightness. Generally ranging from 0 to 10. Properly stored microscopes should always have their rheostats adjusted to 0 to minimize possible bulb filament breakage if the power is switched on with too high an initial voltage.
Define power switch
Controls the application of electrical power to the rheostat.
Define light source
Generally a tungsten filament bulb
Define magnification
The relative enlargement of the image. Total magnifications are calculated by multiplying the magnification of each lens the light passes through after passing through the specimen. For the microscopes in this lab total magnification is calculated by multiplying the power of the objective and ocular lenses
Define resolution
The ability of a microscope to enable visualization of two closely spaced points on a specimen. In practice, known as the resolving power of a microscope, the lower the resolving power the better the resolution
Define resolving power
Defined as the smallest distance between two points where those two points are clearly visible. Mathematically related as follows: RP = wavelength / (NAobj. + NAcond.), where NA is the numerical aperture of either the objective or condenser lens systems. Numerical aperture = n (Sin0), where n is the lens refractive index and 0 is the angle from the center of the beam of light as it passe through the specimen to the outer edge of the objective lens.
Define refraction
The bending of light
Define refractive index
Different substances that will transmit light have different refractive indices. Air has a refractive index of 1.0, glass is about 1.5, and immersion oil is very close to 1.5
Define immersion oil
A highly purified oil used to fill the space between the specimen and the objective and condenser lenses. Usually, for the sake of keeping the microscope clean, the oil is not added to the bottom of the slide. When added the oil displaces the air, reducing refraction of light passing through the specimen. This decreases the resolving power of the lens system, increasing the microscope’s resolution. We only use this on 1000x
Define focal length
The specific working distance of the lens system when the specimen is in focus to the observer
Define parfocal
A geometric property of a lens system and microscope allowing for nearly focused images when switching from a focused lower objective magnification to a higher power lens (which should be in focus with minimal movement of the fine focus).
Define working distance
The space between a focused objective lens and the surface of the slide. For lenses on typical microbiology laboratory microscopes the working distances are as follows: 4x, about 2cm; 10x, about .5cm; 40x, about .4mm; and 100x, about .1mm
All culture media must provide what components?
1) Major elemetns (C, H, O, N, P, S)
2) Minor elements (Fe, Ca, K, Mg, etc)
3) Trace needs (e.g., vitamins)
4) An energy source
5) Buffering capacity
6) Special needs (e.g. unique terminal electron acceptors or donors, unique temperatures or other physical parameters)
What are the two types of bacterial media?
Complex or defined
Define broth
A liquid based medium provided in either tube or flask. Broth tubes are filled after thorough mixing. These broth tubes must be sterilized to ensure having sterile media for your cultures
Define agar
An extract of seaweed that can be used to make a solid, gel-like product after heat sterilization. The spaces within the agar matrix will be filled with whatever aqueous phase was mixed with the agar initially. Thus, beef-based, soy-based, and any number of aqueous additions can be made.
Define petri dish
A shallow dish with a loose fitting lid designed to hold a relatively small volume of molten agar, which then solidifies, giving a sold flat surface to grow cultures. They can be made out of glass or plastic; most are plastic and come pre-sterilized
Define agar slant
Agar-based media poured into a test tube prior to heat sterilization; upon removal from the autoclave, these tubes are placed on a slant and allowed to cool where they solidify, leaving a solid slanted surface in the tube. Media produced in slants is much less susceptible to drying than in agar petri dishes.
Define complex medium
The major constituents of this medium are provided by extracting components of plants or animals; the most common being soybean or beef based, because they provide a complex mixture of carbohydrates, proteins, lipids, nucleic acids, and other elements not easily defined. In general complex media are used to grow the largest number of different types of bacteria.
What were the two types of media used in lab 2?
Tryptic soy broth (TSB) and tryptic soy agar (TSA)
Define an autoclave
A device used to sterilize equipment/ supplies by subjecting them to high pressure saturated steam at 121C for 15-20 minutes
What do you use with a magnetic stirrer?
A hot plate
Describe what was done with the TSB media in lab 2
1) Measured out 9 grams of TSB powder and combined with water in a flask to produce 300ml of media
2) Transferred 10ml of the media to each of the 30 tubes
3) Capped the tubes, and removed one tube and labelled it as “nonsterile”
4) Tubes were then put in the autoclave
Describe what was done with the TSA in lab 2
1) Measured out 9 grams of TSB powder and mixed with 4.5 grams of agar as well as water to make 300ml of molten agar; a hot plate and magnetic stirrer were used to ensure it was mixed well.
2) Transferred 12ml of the solution into 25 tubes
3) Capped the tubes and labelled them as TSA slants
4) Autoclave
Describe how autoclaves work
They work because moist heat kills due to:
1) Increased motion of molecules
2) Cleavage of H bonds in/between proteins
3) Water molecules in steam become more energized
4) More penetration (into liquids/ surfaces)
Describe what was learned in lab 2 overall
The preparation of bacterial culture-based media
What are the 3 main reasons aseptic technique is important?
1) Safety: When working with cultures to minimize potential contamination of you and your neighbor
2) Sterility: When working with sterile substances to avoid contamination
3) Purity: When working with pure cultures
How do you aseptically pour tryptic soy agar (TSA) plates?
1) Flask closed; open and pass over the flame
2) Pour into petri dish
3) Recap petri dish and pass the flask over the flame again
4) Recap the flask
* All of this must be done within ~1.5 feet of a flame
How do you aseptically transfer a bacterial pure culture?
1) Sterilize the loop with a flame
2) Pass the lid of the culture’s tube over the flame
3) Open tube, put loop in the tube and collect bacteria
4) Close bacteria tube
5) Open the sterilized petri dish or tube and deposit bacteria with the loop
6) Re-sterilize loop
* All must be done within ~1.5 feet of a flame
When working with ‘dry’ bacteria (i.e. in a petri dish of agar), why is it important to slowly put the loop into the flame slowly when re-sterilizing?
So you don’t accidently allow the bacteria to go airborne
Define colonial morphology
The outwardly visible structure, color, and odor of colonies of a pure culture of bacteria, used to characterize that culture
