MICROBIOLOGY GCU LAB FINAL
REVIEW STUDY GUIDE 2026
COMPLETE QUESTIONS WITH
CORRECT DETAILED ANSWERS || 100%
GUARANTEED PASS <RECENT
VERSION>**
Microbiology Lab Final Review: 100 Q&A
Section 1: Laboratory Safety and Aseptic Technique
1. What is the primary purpose of aseptic technique in microbiology?
A) To make experiments more complicated
B) To prevent contamination of cultures and the environment
C) To ensure bacteria grow faster
D) To sterilize all equipment visually
2. What is the minimum recommended time for sterilizing inoculating
loops and needles in an incinerator?
A) 2 seconds
B) 5-10 seconds
C) 30 seconds
D) 1 minute
3. After flaming the loop, how long should you wait before picking up a
sample?
A) Don't wait, do it immediately
B) 5-10 seconds to allow it to cool
C) 30 seconds
D) 1 minute
, 4. What should you always wear in the microbiology lab?
A) Sandals and shorts
B) Safety goggles and closed-toe shoes
C) Contact lenses instead of glasses
D) Your favorite sweater
5. What is the correct first step if you spill a live bacterial culture on the
bench?
A) Run and tell the instructor immediately
B) Hide it and pretend it didn't happen
C) Cover the spill with paper towels and saturate with disinfectant, then
notify the instructor
D) Wipe it up with a dry paper towel
Section 2: Microscopy and Staining
6. What is the total magnification when using the oil immersion objective
lens (100X)?
A) 100X
B) 400X
C) 1000X
D) 2000X
7. Why is immersion oil used with the 100X objective?
A) To clean the lens
B) To prevent the lens from scratching the slide
C) To reduce light refraction and increase resolution
D) To slow down the growth of bacteria
8. The primary purpose of heat fixation during a simple stain is to:
A) Melt the cell wall
B) Kill the bacteria and adhere them to the slide
C) Make the cells more visible without stain
D) Sterilize the slide
9. A Gram stain is an example of what type of staining procedure?
A) Simple stain
, B) Negative stain
C) Differential stain
D) Flagellar stain
10.What is the correct order of reagents in the Gram stain?
A) Safranin, Iodine, Crystal Violet, Alcohol
B) Crystal Violet, Iodine, Alcohol, Safranin
C) Iodine, Crystal Violet, Safranin, Alcohol
D) Crystal Violet, Alcohol, Iodine, Safranin
11.Gram-positive bacteria stain what color?
A) Pink/Red
B) Purple/Violet
C) Green
D) Colorless
12.Gram-negative bacteria stain what color?
A) Pink/Red
B) Purple/Violet
C) Green
D) Blue
13.The critical step that differentiates Gram-positive from Gram-negative
cells is the:
A) Crystal Violet application
B) Iodine mordant application
C) Alcohol decolorization
D) Safranin counterstain application
14.If you under-decolorize a Gram stain, what is the likely result?
A) All cells will appear pink
B) All cells will appear purple
C) Gram-positive cells will appear pink
D) No cells will be visible
15.If you over-decolorize a Gram stain, what is the likely result?
A) All cells will appear pink
REVIEW STUDY GUIDE 2026
COMPLETE QUESTIONS WITH
CORRECT DETAILED ANSWERS || 100%
GUARANTEED PASS <RECENT
VERSION>**
Microbiology Lab Final Review: 100 Q&A
Section 1: Laboratory Safety and Aseptic Technique
1. What is the primary purpose of aseptic technique in microbiology?
A) To make experiments more complicated
B) To prevent contamination of cultures and the environment
C) To ensure bacteria grow faster
D) To sterilize all equipment visually
2. What is the minimum recommended time for sterilizing inoculating
loops and needles in an incinerator?
A) 2 seconds
B) 5-10 seconds
C) 30 seconds
D) 1 minute
3. After flaming the loop, how long should you wait before picking up a
sample?
A) Don't wait, do it immediately
B) 5-10 seconds to allow it to cool
C) 30 seconds
D) 1 minute
, 4. What should you always wear in the microbiology lab?
A) Sandals and shorts
B) Safety goggles and closed-toe shoes
C) Contact lenses instead of glasses
D) Your favorite sweater
5. What is the correct first step if you spill a live bacterial culture on the
bench?
A) Run and tell the instructor immediately
B) Hide it and pretend it didn't happen
C) Cover the spill with paper towels and saturate with disinfectant, then
notify the instructor
D) Wipe it up with a dry paper towel
Section 2: Microscopy and Staining
6. What is the total magnification when using the oil immersion objective
lens (100X)?
A) 100X
B) 400X
C) 1000X
D) 2000X
7. Why is immersion oil used with the 100X objective?
A) To clean the lens
B) To prevent the lens from scratching the slide
C) To reduce light refraction and increase resolution
D) To slow down the growth of bacteria
8. The primary purpose of heat fixation during a simple stain is to:
A) Melt the cell wall
B) Kill the bacteria and adhere them to the slide
C) Make the cells more visible without stain
D) Sterilize the slide
9. A Gram stain is an example of what type of staining procedure?
A) Simple stain
, B) Negative stain
C) Differential stain
D) Flagellar stain
10.What is the correct order of reagents in the Gram stain?
A) Safranin, Iodine, Crystal Violet, Alcohol
B) Crystal Violet, Iodine, Alcohol, Safranin
C) Iodine, Crystal Violet, Safranin, Alcohol
D) Crystal Violet, Alcohol, Iodine, Safranin
11.Gram-positive bacteria stain what color?
A) Pink/Red
B) Purple/Violet
C) Green
D) Colorless
12.Gram-negative bacteria stain what color?
A) Pink/Red
B) Purple/Violet
C) Green
D) Blue
13.The critical step that differentiates Gram-positive from Gram-negative
cells is the:
A) Crystal Violet application
B) Iodine mordant application
C) Alcohol decolorization
D) Safranin counterstain application
14.If you under-decolorize a Gram stain, what is the likely result?
A) All cells will appear pink
B) All cells will appear purple
C) Gram-positive cells will appear pink
D) No cells will be visible
15.If you over-decolorize a Gram stain, what is the likely result?
A) All cells will appear pink
