Final answer:
Exotoxins are heat-labile proteins mainly produced by gram-positive bacteria, causing specific cellular damage, whereas endotoxins are heat-stable lipopolysaccharides found in gram-negative bacteria, responsible for general inflammatory responses.
Step-by-step explanation:
Correctly matching the structure to the toxin, we find that exotoxins are protein molecules produced predominantly by gram-positive bacteria and some gram-negative pathogens. These proteins have a high specificity for the cells they target, utilizing unique molecular mechanisms to cause damage to those cells. Exotoxins are also heat labile and are typically denatured at temperatures above 41 °C (106 °F).
On the other hand, endotoxins are lipopolysaccharides (LPS), specifically the lipid A component found in the outer membrane of gram-negative bacteria. Endotoxins stimulate a general systemic inflammatory response and are relatively stable to heat, requiring temperatures of 121 °C (250 °F) for at least 45 minutes to be inactivated. The lethality of endotoxins is significantly less than that of exotoxins, with higher required concentrations to cause lethal effects.