Page 1 of 109
,Page 2 of 109
BIOD171 (Latest ) Microbiology
Lab 1-9 Exams Portage Learning, 100 %
Guaranteed Pass ||Complete A+ Guide
1. Which objective lens requires oil immersion?
A) 4x
B) 10x
C) 40x
D) 100x
Answer: D) 100x
Rationale: The 100x objective has a very short working
distance; oil prevents light refraction, improving resolution.
2. What is the total magnification when using a 10x ocular
and a 40x objective?
,Page 3 of 109
A) 40x
B) 100x
C) 400x
D) 4000x
Answer: C) 400x
Rationale: Total magnification = ocular × objective = 10 ×
40 = 400x.
3. Which stain is used in the Gram stain to counterstain Gram-
negative bacteria?
A) Crystal violet
B) Iodine
C) Safranin
D) Methylene blue
Answer: C) Safranin
Rationale: Safranin stains Gram-negative cells pink after
alcohol decolorization.
, Page 4 of 109
4. The purpose of heat-fixing a smear is to:
k k k k k k k
A) Stain the bacteria
k k
B) Kill bacteria and adhere them to the slide
k k k k k k k
C) Enhance motility k
D) Decolorize the cells k k
Answer:B)KillbacteriaandadherethemtotheslideRationale:
k k k k k k k k k k
Heat fixation kills cells and fixes them to the slide withoutdistorting
k k k k k k k k k k k k
morphology.
k
5. Which of the following is a simple stain?
k k k k k k k
A) Gram stain k
B) Acid-fast stain k
C) Methylene blue k
D) Endospore stain k
,Page 2 of 109
BIOD171 (Latest ) Microbiology
Lab 1-9 Exams Portage Learning, 100 %
Guaranteed Pass ||Complete A+ Guide
1. Which objective lens requires oil immersion?
A) 4x
B) 10x
C) 40x
D) 100x
Answer: D) 100x
Rationale: The 100x objective has a very short working
distance; oil prevents light refraction, improving resolution.
2. What is the total magnification when using a 10x ocular
and a 40x objective?
,Page 3 of 109
A) 40x
B) 100x
C) 400x
D) 4000x
Answer: C) 400x
Rationale: Total magnification = ocular × objective = 10 ×
40 = 400x.
3. Which stain is used in the Gram stain to counterstain Gram-
negative bacteria?
A) Crystal violet
B) Iodine
C) Safranin
D) Methylene blue
Answer: C) Safranin
Rationale: Safranin stains Gram-negative cells pink after
alcohol decolorization.
, Page 4 of 109
4. The purpose of heat-fixing a smear is to:
k k k k k k k
A) Stain the bacteria
k k
B) Kill bacteria and adhere them to the slide
k k k k k k k
C) Enhance motility k
D) Decolorize the cells k k
Answer:B)KillbacteriaandadherethemtotheslideRationale:
k k k k k k k k k k
Heat fixation kills cells and fixes them to the slide withoutdistorting
k k k k k k k k k k k k
morphology.
k
5. Which of the following is a simple stain?
k k k k k k k
A) Gram stain k
B) Acid-fast stain k
C) Methylene blue k
D) Endospore stain k
