Final answer:
Endotoxins are composed of lipopolysaccharide, require small doses to cause toxic effects, and are heat-stable.
Step-by-step explanation:
Endotoxins have several characteristic traits that differentiate them from exotoxins. Firstly, endotoxins are composed of lipopolysaccharide (LPS), while exotoxins are protein molecules. Secondly, a very small dose of endotoxins is required to cause toxic effects, whereas exotoxins can be lethal even in small concentrations. Lastly, endotoxins are heat-stable, whereas exotoxins are heat-labile and can be denatured at high temperatures.