Peptidoglycan is a complex polymer that forms a key structural component of bacterial cell walls. It is made up of sugar molecules (glycan) and peptides (short chains of amino acids). The sugar component consists of alternating units of **N-acetylglucosamine (NAG)** and **N-acetylmuramic acid (NAM)**, while the peptide chains cross-link these sugar units, providing strength and rigidity to the cell wall.

Peptidoglycan is crucial for maintaining the shape of the bacterial cell, protecting it from osmotic pressure, and preventing lysis (bursting). It's also a target for many antibiotics, like penicillin, which disrupts peptidoglycan synthesis, weakening the bacterial cell wall and leading to cell death.