The Prokaryotic Cell
|The typical bacterial cell wall consists of peptidoglycan polymers, polypeptide chains cross-linked with short peptides. The cell wall prevents swelling due to the osmotic imbalance of the bacteria being hypertonic to the surrounding fluid.|
It is important for the MCAT to know that differences in the peptidoglycan cell wall are the basis for the differences in bacteria observed in Gram staining. Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan while Gram-negative bacteria have a thinner cell wall as well as a lipopolysaccharide outer membrane. A bacterium might additionally possess a thick outer capsule or have pili present.