Which of the following functional groups is commonly used in the Gram staining technique in microbiology?

• A. $\text{Hydroxyl group}\left(O^H\right)$
• B. $\text{Amino group}\left(N^H\right)$
• C. $\text{Iodine complex with crystal violet}(I_2+\text{crystal violet})$
• D. $\text{Carboxyl group}(C^{O}OH)$

Answer: (C)

Verified step by step guidance

1. Understand the context of the Gram staining technique: Gram staining is a method used to differentiate bacterial species into two groups based on the physical and chemical properties of their cell walls.
2. Identify the role of functional groups in Gram staining: The technique involves the use of crystal violet dye, iodine, and a decolorizing agent. The iodine forms a complex with crystal violet, which is crucial for the staining process.
3. Recognize the functional groups listed: Hydroxyl group (-OH), Amino group (-NH2), and Carboxyl group (-COOH) are common functional groups in organic chemistry, but they are not directly involved in the Gram staining process.
4. Focus on the iodine complex: The iodine complex with crystal violet is the key component in Gram staining, as it helps to fix the dye within the bacterial cell wall, allowing differentiation between Gram-positive and Gram-negative bacteria.
5. Conclude that the iodine complex with crystal violet is the correct answer, as it is the functional group involved in the Gram staining technique, rather than the hydroxyl, amino, or carboxyl groups.