LPS, or lipopolysaccharide, is a large molecule found in the outer membrane of Gram-negative bacteria. It consists of a lipid portion, known as lipid A, and a polysaccharide component. LPS plays a crucial role in the structural integrity of the bacterial cell wall and can trigger strong immune responses in humans and animals. When LPS enters the body, it can activate the immune system, leading to inflammation. While this response is essential for fighting infections, excessive LPS can cause severe reactions, such as sepsis. Understanding LPS is important for developing treatments for bacterial infections and managing immune responses.