What is the bacterial cell wall composed of in layers?

The bacterial cell wall is primarily composed of layers of peptidoglycan, also known as murein, which is a unique structural polymer found exclusively in bacteria. Peptidoglycan consists of long chains of sugars (called glycan) cross-linked together by short chains of amino acids (called peptides), forming a strong mesh-like network around the bacterial cell. Every student must remember that this peptidoglycan layer gives bacteria their characteristic shape and provides essential mechanical strength to protect the cell from bursting due to osmotic pressure.

• Structure: Made up of alternating sugar units — N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) — linked by peptide chains
• Gram-Positive Bacteria: Possess a thick peptidoglycan layer, which is why they retain the violet stain during Gram staining
• Gram-Negative Bacteria: Have a much thinner peptidoglycan layer along with an additional outer membrane
• Other Options: Chitin is found in fungal cell walls and insect exoskeletons, while cellulose makes up plant cell walls — neither is present in bacteria
• Antibiotic Target: Many antibiotics like penicillin specifically destroy peptidoglycan synthesis, killing bacteria without harming human cells