In the presence of penicillin, a bacterial cell dies because:

• A. penicillin disrupts the function of ribosomes, preventing protein synthesis
• B. penicillin blocks the electron transport chain in the plasma membrane
• C. penicillin interferes with DNA replication by binding to DNA polymerase
• D. penicillin inhibits the synthesis of peptidoglycan in the cell wall

Answer: (D)

Verified step by step guidance

1. Understand the role of penicillin: Penicillin is an antibiotic that targets bacterial cell wall synthesis, specifically the peptidoglycan layer.
2. Recall the structure and function of peptidoglycan: Peptidoglycan provides mechanical strength to the bacterial cell wall, preventing osmotic lysis.
3. Recognize that penicillin inhibits enzymes called transpeptidases (also known as penicillin-binding proteins) which are responsible for cross-linking peptidoglycan strands.
4. Understand that without proper cross-linking, the cell wall becomes weak and unable to maintain cell integrity, leading to cell lysis and death.
5. Note that penicillin does not affect ribosomes, electron transport chain, or DNA polymerase, so the other options are incorrect.