Which component is found in the external covering of Gram-positive cells, but not in Gram-negative cells?

• A. Periplasmic space
• B. Teichoic acids
• C. Lipopolysaccharide
• D. Outer membrane

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the structural differences between Gram-positive and Gram-negative bacterial cell walls. Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane.
2. Step 2: Identify the components unique to Gram-positive bacteria. Teichoic acids are polymers found embedded in the thick peptidoglycan layer of Gram-positive bacteria and contribute to cell wall maintenance and ion regulation.
3. Step 3: Recognize that Gram-negative bacteria have an outer membrane containing lipopolysaccharides (LPS), which are absent in Gram-positive bacteria.
4. Step 4: Note that the periplasmic space is present in Gram-negative bacteria between the outer membrane and the plasma membrane, but it is either absent or very minimal in Gram-positive bacteria.
5. Step 5: Conclude that teichoic acids are found in the external covering of Gram-positive cells but not in Gram-negative cells, distinguishing them from components like lipopolysaccharide and the outer membrane.