Homework Questions: Exam One
List three elements of an effective hand washing technique or procedure
- Use soap - Wash for 20 to 40 seconds - Scrubbing
Resolving power
The ability to distinguish between two particles
Joesph Lister
promoted the idea of sterile surgery
List in order of largest to smallest of organisms: bacteria, yeast, mold, and protozoa
mold (largest), yeast, protozoa, bacteria, virus (smallest)
What are the two morphological forms of fungi
mold and yeast
simple stain
used to determine cell shape, size, and arrangement (contrast which enables better visualization of cell and cell parts)
gram stain
used to differentiate two large groups of bacteria based on their different cell walls
95% ethanol (gram stain reagent)
(3) decolorizing and destroys lipids of the membrane
safranin (gram stain reagent)
(4) stain pink cells that have already been decolorized
What is the purpose of fixing a slide?
Done by heat to kill the cell so the bacteria don't wash off the slide during the staining process (attachment to slide)
Entamoeba Histolytica: Endospore
Dormant Resistent
Most viruses are too small to be observed using a compound light microscope. Indicate the type of microscope that could be used to view viruses.
Electron microscope
What is meant by the limit of resolution? What is the maximum resolving power of the compound light microscope?
Means that it is restricted by wavelength of visible light. A compound light microscope can have a max of 200x
At what point in history did the medical profession adopt practices consistent with Dr. Semmelweis' practice?
Mid to late 1800s
Entamoeba Histolytica: Trophozote
Moves Cats Reproduces
What is meant by the term parfocal? What is the advantage of the parfocal lens?
Things stay in focus when magnification is changed, this works as an advantage when changing between lower to higher lenses or vice versa.
What do we call the handwashing techniques used by Dr. Semmelweis?
Antiseptic techniques
What is the function of the iris diaphragm?
Controls the amount of light reaching the slide Compares to the cornea in the eye
Why are unstained bacteria more difficult to observe than stained bacteria?
The stained bacteria would be more contrasted than the unstained bacteria
crystal violent (gram stain reagent)
(1) stains the cell
iodine (gram stain reagent)
(2) binds to crystal violet and makes it less soluble
Magnifying power
enlarges the image
What is childbed fever?
A bacterial infection of the female reproductive tract following childbirth or miscarriage
What is the total magnification achieved with the compound light microscope used in lab if one is using the 10x objective lens to view a specimen?
A normal lens is 10x magnification, but 10x low power lens (10x10=100) you have 100x magnification
What did Dr. Ignaz Semmelweis (1818-1865) propose as an effective means of preventing childbed fever?
He had his students wash their hands and this reduced the number of cases signifigantly
What evidence did Dr. Ignaz Semmelweis have as apart of his hypothesis?
He said that the med students carried "cadaver particles" from their autopsy to the delivery rooms and that these particles resulted in puerperal fever
Given the potential difficulty in observing an unstained microbe why would someone bother to view a microbe using a wet mount (where the organism is not stained)
If you wanted to view a live organism you wouldn't stain it; the stain kills the cell
What is the function of the substage condenser?
It focuses light onto a small area
wet mount
allows you to view living organisms (intact structures) and study their movement and behevior
Why is hand washing important?
it is the single most effective measure to prevent the spread of virulent or antibiotic resistant bacteria in hospitals