Chapter 3

Question 1

Steps for Gram Staining

Answer 1

1) A heat fixed smear is covered with a basic purple dye (crystal violet). Know as the primary stain.
2) After a short time, the purple dye is washed off and the smear is covered with iodine, a mordant. When iodine is washed off, all bacteria appear dark violet or purple.
3) Next, the slide is washed with alcohol. This is a decolorizing agent, which removes the purple from the cells of some species, but not from all.
4)The alcohol is rinsed off, and the slide is then stained with safranin, a basic red dye. The smear is then washed again, blotted dry, and looked at under a microscope.

Question 2

What is a mordant in the staining process?

Answer 2

They are used to make the mircoorganisms stain more intensely

Question 3

Why are mordants important?

Question 4

What are the steps to making a smear?

Answer 4

1) Label your slide. …
2) Pick a well-isolated colony.
3) Prick it with your sterile needle, or slightly scoop the edge of the colony with your sterile loop.
4) Place your needle/loop in the center of the drop and with a spiraling circular motion spread the bacteria on the slide.
5) Set the slide aside to air dry.

Question 5

why is the sample fixed on the microscope slide?

Answer 5

to prevent decay and preserve the cells

Question 6

Simple stains are used to improve contrast in what type of microscope?

Answer 6

Compound Light microscopy

Question 7

What type of microscope has the highest magnification and greatest resolution?

Answer 7

Electron microscopy

Question 8

how to calculate total magnification of a microscope

Answer 8

Objective Power x Ocular Power = Total Magnification

Question 9

Which step in gram staining differentiates between Gram positive and Gram negative cells?

Answer 9

step 3 when it’s decolorizing

Question 10

resolution

Answer 10

ability of the microscope to distinguish two points

Question 11

Why is Gram staining useful?

Answer 11

checks for bacteria at the site of a suspected infection