Chapter Exam

Chapter 3: Stains and Staining Methods — Online MCQ Test

Q: Which of the following is an example of a basic dye used in microbiology?

Answer: A. Methylene blue — Methylene blue is a basic dye which binds to negatively charged cellular components like nucleic acids.

Q: In Gram staining, what is the role of Iodine?

Answer: B. Mordant — Iodine acts as a mordant by forming a crystal violet-iodine complex that is trapped inside the thick peptidoglycan of Gram-positive cells.

Q: If you forget the decolorization step in a Gram stain, what would be the appearance of both Gram-positive and Gram-negative organisms?

Answer: A. Both purple — Without decolorization, the primary stain (crystal violet) remains in all cells, masking the effect of the counterstain.

MICROBIOLOGY · CLASS 11th · Tamil Nadu State Board

Practice Chapter 3: Stains and Staining Methods with a free chapter-wise online MCQ test for Tamil Nadu State Board CLASS 11th MICROBIOLOGY. This chapter covers: This chapter details dye chemistry fixatives and staining techniques used in microbiology. Students examine simple differential Gram staining acid-fast staining structural capsule.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 3: Stains and Staining Methods — Important Questions & Answers (FAQ)

Frequently asked questions from Tamil Nadu State Board CLASS 11th MICROBIOLOGY — Chapter 3: Stains and Staining Methods, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following is an example of a basic dye used in microbiology?

A. Methylene blue ✓
B. Eosin
C. Nigrosin
D. India ink

Answer: A. Methylene blue
Methylene blue is a basic dye which binds to negatively charged cellular components like nucleic acids.

What is the primary function of a fixative in staining procedures?

A. To kill the bacteria and attach them to the slide ✓
B. To provide color to the cell wall
C. To increase the magnification
D. To act as a decolorizer

Answer: A. To kill the bacteria and attach them to the slide
Fixation kills the microorganisms, preserves their structures, and ensures they adhere firmly to the microscope slide.

In Gram staining, what is the role of Iodine?

A. Primary stain
B. Mordant ✓
C. Decolorizer
D. Counterstain

Answer: B. Mordant
Iodine acts as a mordant by forming a crystal violet-iodine complex that is trapped inside the thick peptidoglycan of Gram-positive cells.

If you forget the decolorization step in a Gram stain, what would be the appearance of both Gram-positive and Gram-negative organisms?

A. Both purple ✓
B. Both pink
C. Gram-positive pink, Gram-negative purple
D. Both colorless

Answer: A. Both purple
Without decolorization, the primary stain (crystal violet) remains in all cells, masking the effect of the counterstain.

Which of the following statements about Gram staining is correct regarding the cell wall composition?

A. Gram-positive walls have higher lipid content than Gram-negative walls
B. Gram-negative walls have a thinner peptidoglycan layer and an outer membrane ✓
C. Gram-positive walls possess an outer membrane rich in LPS
D. Gram-negative walls are impermeable to alcohol

Answer: B. Gram-negative walls have a thinner peptidoglycan layer and an outer membrane
Gram-negative cell walls contain a thin peptidoglycan layer that allows the crystal violet-iodine complex to be easily washed out during decolorization.

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