Final answer:
The true statement about endotoxins is that they are released when gram-negative bacteria die and their cell walls break down. Endotoxins are part of the outer membrane of gram-negative bacteria, and they consist mainly of lipid A within the lipopolysaccharide complex.
Step-by-step explanation:
Among the options provided regarding endotoxins, the accurate statement is that endotoxins are released when bacteria die and their cell walls break down. Endotoxins are a component of the outer membrane of gram-negative bacteria. Specifically, they are part of the lipopolysaccharide (LPS) complex, with the toxic component being lipid A. When gram-negative bacteria die or divide, they can release endotoxin into the surrounding environment.
The other statements are inaccurate concerning endotoxins. Endotoxins are not proteins, they are lipid components; they are not typical products of gram-positive bacteria; and they do not derive from endospores. Clostridium botulinum, which produces the botulinum toxin, is an example of a bacterium that produces exotoxins, not endotoxins. Exotoxins, unlike endotoxins, are protein molecules secreted by certain bacteria and have very different properties, including being generally more potent and temperature-sensitive.