Why are most Gram-negative bacteria resistant to the actions of penicillin View Available Hint(s) Penicillin is unable to pass through the thick layer of peptidoglycan. Penicillin is unable to pass through the outer membrane of the cell wall. Penicillin is unable to pass through the teichoic acid barrier. Gram-negative bacteria lack a peptidoglycan cell wall. Submit

To understand why most Gram-negative bacteria are resistant to the actions of penicillin, we need to consider the structure of their cell walls. 1. **Cell Wall Structure**: - Gram-negative bacteria have a unique cell wall structure that consists of a thin layer of peptidoglycan surrounded by an outer membrane. - The outer membrane contains lipopolysaccharides and proteins, which serve as a barrier to many substances, including antibiotics like penicillin. 2. **Penicillin Mechanism**: - Penicillin works by inhibiting the synthesis of peptidoglycan, which is crucial for bacterial cell wall integrity. - In Gram-positive bacteria, the thick peptidoglycan layer is directly exposed to penicillin, allowing the antibiotic to effectively disrupt cell wall synthesis. 3. **Resistance in Gram-negative Bacteria**: - In Gram-negative bacteria, the outer membrane acts as a protective barrier that prevents penicillin from reaching the peptidoglycan layer. - Therefore, the correct reason for the resistance of most Gram-negative bacteria to penicillin is that **penicillin is unable to pass through the outer membrane of the cell wall**. Thus, the answer is: **Penicillin is unable to pass through the outer membrane of the cell wall.**