biol_220_demonstration_quiz_20240316210343

Question 1

What can differential staining help determine?

Answer 1

Cell shape, arrangement, size, and identification

Question 2

What is the most common way to differentiate two groups of bacteria?

Answer 2

Gram staining is a common way to differentiate between two groups of bacteria is through their cell wall components. It is a 2-part procedure where you prepare and take a specimen and proceed with the staining process.

Question 3

What are the differences in staining and bacterial cell walls in gram-positive and gram-negative?

Answer 3

Gram-positive: Purple or Violet, Large amounts of Peptidoglycan in cell wall layer
Gram-negative: Red or Pink, little amounts of Peptidoglycan in cell wall layer

Question 4

What is the function of Iodine?

Answer 4

Iodine acts as a mordant, which helps the dye stick to the smear.

Question 5

Which dye does iodine act as a mordant to?

Answer 5

Crystal Violet

Question 6

How does alcohol aid in the staining process?

Answer 6

Alcohol acts as a decolorizer and washes off the dye from gram-negative bacteria. Alcohol also dissolves the lipids found in the outer cell membrane of gram-negative bacteria to allow safranin to adhere to the bacteria.

Question 7

Colorless bacterial cell wall is ______ charged.

Answer 7

Negatively

Question 8

What allows dyes to bind to cell walls?

Answer 8

Dyes have chromophores that are positively charged. Opposite charges are attracted to one another which allows the dyes to bind to the cell wall (peptidoglycan layer).

Question 9

What happens if you run the alcohol for too long?

Answer 9

If you run the alcohol for more than 20 seconds, you will get false gram-negative results when it should be gram-positive.

Question 10

What happens if you run the alcohol for too little?

Answer 10

If you run the alcohol for less than 20 seconds, you will get false gram-positive results when it should be gram-negative.