Lecture 3 Flashcards
(46 cards)
All of the following are examples of light microscopy EXCEPT ______.
A) Electron
B) Fluorescent
C) Dark-field
D) Phase-contrast
Electron
Electron microscopy uses beams of electrons instead of rays of light. Electron microscopy can achieve far better resolution than light microscopy can.
All of the following are examples of differential stains EXCEPT______.
A) Spore stain
B) Gram stain
C) Acid-fast stain
D) Metheylene blue
Methylene blue
In microscopy, the ability to distinguish two objects separated by a small distance is _________.
Resolution
In microscopy, ______ is the smallest distance by which two objects can be separated and still be distinguished.
Resolution
The main reason we stain organisms while viewing them is ?
To increase contrast of organisms from the surrounding medium.
To increase resolution, all factors must be considered EXCEPT ______.
A) a detector (lens) with sufficient resolution for the given wavelength
B) the wavelength should be smaller than the object
C) the contrast between the object and its surroundings
D) the type of bacteria
the type of bacteria
To increase resolution, several factors are considered:
wavelength, light and contrast, and lens quality
What is the wavelength of visible light?
400–750 nm
When bacterial samples are made to adhere to the slide, this process is called ______.
fixation
Cells may be fixed with _____ or by _____ treatment.
methanol; heat
_____ is the bending of light as it enters a substance that slows its speed.
Refraction
While performing a gram stain on a mixed culture, your cell phone rings and you accidentally leave the decolorizing solution on too long. What color would you predict your gram-positive cells to be upon completion of the procedure?
A) Blue
B) Colorless
C) Pink
D) Purple
Pink
The decolorizing step is the most critical step while performing a gram stain. Leaving the decolorizing solution on too long will result in the over-decolorizing of the gram-positive cells, causing them to lose their purple stain. Upon the addition of the safranin stain, all cells will stain pink.
Gram positives have more ____ in their outer layer than negatives.
Peptidoglycan
5 examples of differential stains:
- Gram
- Acid-fast
- Endospore
- Flagella
- Capsule
Steps in gram staining:
- Add methanol/heat to fix cells to slide
- Add crystal violet
- Add iodine, which binds stain to cells
- Wash with ethanol to decolorize (dehydrates cell)
- Crystal violet stain is removed from gram negatives
- Add safranin counter stain
- Safranin stains gram negatives
Carbohydrates are made up of what elements in what ratio?
C:H:O in a 1:2:1 ratio
The simplest carbohydrates are called ?
Monosaccharides
Two bonded monosaccharides are called ?
Disaccharides
The reaction to bond two monosaccharides is called ?
Dehydration
The reaction break apart a disaccharide is called ?
Hydrolysis
Lipids are usually polar or non-polar?
Non-polar
What type of bond between two amino acids?
Peptide bond
What happens when a protein loses it’s shape due to temperature, pH, or salt?
Denaturation
Name the nitrogenous bases in DNA.
Adenine, Thymine, Guanine, & Cytosine
