This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Endotoxin from gram negative organism is: 
Select and explain. 
A. Polysaccharide, B. Glycoprotein, C. Lipoprotein, D. Lipopolysaccharide
D: Lipopolysaccharide
Answer: D: Lipopolysaccharide 
Explanation: Ans. (d) Lipopolysaccharide Ref. Alum ilianarayan o/c, p 78, 'able (9.1), 9/e, p 75 Distinguishing features of exotoxins and endotoxins Proteins Heat labile Actively secreted by cells; diffuse into surrounding medium Readily separable from cultures by physical means such as filtration Action usually enzymic Specific pharmacological effects for each exotoxin Specific tissue affinities Active in very minute doses Highly antigenic Action specifically neutralized by antibody Can be toxoided Generally formed by gram positive including some gram negative shigella, vibrio cholera, ETEC, V. parahemolyticus, Aeromonas Y. enterocolitica, P. aeroginosa