Preparation and Staining of Specimens

Question 1

1. Why is staining used in specimen preparation?

a) To reduce the visibility of the specimen
b) To enhance the visibility and morphological features of the specimen
c) To destroy the specimen for future use
d) To protect the specimen from external damage

Answer 1

b) To enhance the visibility and morphological features of the specimen

Question 2

2. What is the main purpose of fixation in specimen preparation?

a) To preserve internal and external structures of cells by inactivating enzymes
b) To dry the specimen completely
c) To destroy the specimen’s morphology
d) To color the specimen for better contrast

Answer 2

a) To preserve internal and external structures of cells by inactivating enzymes

Question 3

4. Which type of fixation preserves fine cellular substructures?

a) Heat fixation
b) Chemical fixation
c) Mechanical fixation
d) None of the above

Answer 3

b) Chemical fixation

Question 4

3. Which of the following is TRUE about heat fixation?

a) It preserves both overall and subcellular morphology
b) It only preserves subcellular structures
c) It preserves overall morphology but destroys subcellular structures
d) It increases the size of the specimen

Answer 4

c) It preserves overall morphology but destroys subcellular structures

Question 5

What is the primary role of dyes in specimen staining?

a) To make the background more visible
b) To destroy the specimen’s structure
c) To reduce the contrast between the specimen and the background
d) To increase the visibility of the cell’s internal and external structures by enhancing contrast

Answer 5

d) To increase the visibility of the cell’s internal and external structures by enhancing contrast

Question 6

Which of the following is a basic dye?

a) Eosin
b) Acid fuchsin
c) Methylene blue
d) Rose bengal

Answer 6

c) Methylene blue

Question 7

What is the charge of a basic dye’s chromophore?

a) Positive
b) Negative
c) Neutral
d) It has no charge

Answer 7

a) Positive

Question 8

Which of the following is an acidic dye?

a) Crystal violet
b) Safranin
c) Acid fuchsin
d) Malachite green

Answer 8

c) Acid fuchsin

Question 9

Simple staining is primarily used to:

a) Visualize specific cell organelles
b) Determine the size, shape, and arrangement of bacteria
c) Identify cell wall components
d) Detect capsules or flagella

Answer 9

b) Determine the size, shape, and arrangement of bacteria

Question 10

What distinguishes differential staining from simple staining?

a) Differential staining divides organisms based on staining properties
b) Differential staining uses only one dye
c) Differential staining destroys the cell wall structure
d) Differential staining is only used for Gram-negative bacteria

Answer 10

a) Differential staining divides organisms based on staining properties

Question 11

Which of the following is NOT a type of differential staining?

a) Gram staining
b) Acid-fast staining
c) Negative staining
d) Flagella staining

Answer 11

c) Negative staining

Question 12

What structural difference is identified by Gram staining?

a) The thickness of the cell membrane
b) Differences in cell wall structure between Gram-positive and Gram-negative bacteria
c) The presence of lipids in the cell wall
d) The arrangement of bacterial flagella

Answer 12

b) Differences in cell wall structure between Gram-positive and Gram-negative bacteria

Question 13

What type of staining is particularly useful for members of the genus Mycobacterium?

a) Gram staining
b) Acid-fast staining
c) Capsule staining
d) Flagella staining

Answer 13

b) Acid-fast staining

Question 14

Which staining method uses phenol and carbol fuchsin?

a) Gram staining
b) Acid-fast staining
c) Simple staining
d) Capsule staining

Answer 14

b) Acid-fast staining

Question 15

What type of staining is used to visualize bacterial capsules?

a) Gram staining
b) Acid-fast staining
c) Negative staining
d) Flagella staining

Answer 15

c) Negative staining

Question 16

Flagella staining uses a mordant to:

a) Change the color of the flagella
b) Increase the visibility of the flagella by thickening them
c) Destroy the bacterial cell wall
d) Decrease the thickness of flagella

Answer 16

b) Increase the visibility of the flagella by thickening them

Question 17

What is the purpose of chemical fixation in specimen preparation?

a) To preserve overall morphology but destroy fine structures
b) To protect fine cellular substructures and preserve cell morphology
c) To dehydrate the specimen
d) To simplify the staining process

Answer 17

b) To protect fine cellular substructures and preserve cell morphology

Question 18

What characteristic is shared by basic dyes?

a) They have negatively charged groups
b) They bind to positively charged molecules
c) They bind to negatively charged molecules like nucleic acids and proteins
d) They are only used for eukaryotic cells
Answer: c) They bind to negatively charged molecules like nucleic acids and proteins

Answer 18

c) They bind to negatively charged molecules like nucleic acids and proteins

Question 19

Which component is typically bound by acidic dyes in cells?

a) Positively charged structures
b) Negatively charged proteins
c) Neutral lipids
d) Subcellular organelles

Answer 19

a) Positively charged structures

Question 20

Which of the following is TRUE regarding ionizable dyes?

a) Basic dyes are negatively charged
b) Acidic dyes have positively charged groups
c) Basic dyes bind to positively charged proteins
d) Acidic dyes bind to positively charged cell structures

Answer 20

d) Acidic dyes bind to positively charged cell structures

Question 21

What is the key feature of simple staining?

a) It divides bacteria into Gram-positive and Gram-negative groups
b) It uses multiple stains to differentiate structures
c) It uses a single stain to enhance contrast and reveal bacterial shape
d) It requires no dyes at all

Answer 21

c) It uses a single stain to enhance contrast and reveal bacterial shape

Question 22

Which of the following is a characteristic of Gram-negative bacteria?

a) They retain the crystal violet stain during Gram staining
b) They appear purple after staining
c) They have a thinner peptidoglycan layer in the cell wall
d) They lack an outer membrane

Answer 22

c) They have a thinner peptidoglycan layer in the cell wall

Question 23

The primary stain used in Gram staining is:

a) Methylene blue
b) Crystal violet
c) Safranin
d) Carbol fuchsin

Answer 23

b) Crystal violet

Question 24

What is the function of the mordant in Gram staining?

a) To color Gram-negative cells
b) To decolorize the cells
c) To wash off excess dye
d) To increase the binding of the primary stain to the bacterial cell wall

Answer 24

d) To increase the binding of the primary stain to the bacterial cell wall

Question 25

Which of the following describes the Ziehl-Neelsen method used in acid-fast staining?

a) It uses crystal violet as the primary stain
b) It uses phenol and carbol fuchsin to stain mycobacteria
c) It distinguishes between Gram-positive and Gram-negative bacteria
d) It is ineffective on bacteria with lipid-rich cell walls

Answer 25

b) It uses phenol and carbol fuchsin to stain mycobacteria

Question 26

What is visualized using capsule staining?

a) The arrangement of bacterial chromosomes
b) The size and shape of bacterial flagella
c) The polysaccharide capsules surrounding bacteria
d) The thickness of bacterial cell walls

Answer 26

c) The polysaccharide capsules surrounding bacteria

Question 27

How are capsules typically visualized in a negative stain?

a) The capsules appear stained while the background remains colorless
b) Both the background and the capsules are stained the same color
c) The capsules remain colorless while the background is stained
d) Only the cell wall is stained, leaving the capsule invisible

Answer 27

c) The capsules remain colorless while the background is stained

Question 28

What information does flagella staining provide?

a) The number and arrangement of bacterial flagella
b) The structure of bacterial chromosomes
c) The shape and size of bacterial capsules
d) The metabolic activity of bacteria

Answer 28

a) The number and arrangement of bacterial flagella

Question 29

Why is a mordant applied during flagella staining?

a) To change the color of the flagella
b) To increase the thickness of the flagella for better visibility
c) To break down the cell wall of the bacteria
d) To separate bacterial flagella from the cell

Answer 29

b) To increase the thickness of the flagella for better visibility

Question 30

Which dye is commonly used in acid-fast staining?

a) Methylene blue
b) Crystal violet
c) Carbol fuchsin
d) Safranin

Answer 30

c) Carbol fuchsin

Question 31

What is the result of decolorizing in Gram staining for Gram-negative bacteria?

a) They retain the crystal violet stain and appear purple
b) They resist decolorization and remain purple
c) They appear blue under the microscope
d) They lose the crystal violet stain and appear colorless until counterstained

Answer 31

d) They lose the crystal violet stain and appear colorless until counterstained

Question 32

In differential staining, what structures can be detected in addition to cell walls?

a) Nuclei and cytoplasm
b) Capsules and flagella
c) Ribosomes and mitochondria
d) Plasmids and chromosomes

Answer 32

b) Capsules and flagella

Question 33

Why is acid-fast staining necessary for mycobacteria?

a) Their lipid-rich cell wall prevents the binding of many standard dyes
b) They do not have cell walls, making standard staining ineffective
c) They lack peptidoglycan, requiring specialized staining
d) They are resistant to basic and acidic dyes

Answer 33

a) Their lipid-rich cell wall prevents the binding of many standard dyes

Question 34

What are three key benefits of staining specimens?

Answer 34

Increases visibility of the specimen.
Accentuates specific morphological features.
Preserves the specimen for future research.