Question

what is a main difference between endotoxins and exotoxins?
endotoxins are lipopolysaccharides and thus structurally integral to the bacterium, whereas exotoxins are proteins that are secreted by living bacteria.
exotoxins are released only when the bacteria die and their cell walls break down.
endotoxins are proteins, and exotoxins are lipopolysaccharides.
exotoxins are made of rna, and endotoxins are made of dna.

Explanation:

To determine the main difference between endotoxins and exotoxins, we analyze each option:

• Option 1: Endotoxins are lipopolysaccharides (LPS) that are part of the bacterial cell wall (structurally integral), and exotoxins are protein toxins secreted by living bacteria. This matches the correct biological understanding.
• Option 2: Endotoxins (not exotoxins) are released when bacteria die and cell walls break down. So this is incorrect.
• Option 3: The chemical nature is reversed; endotoxins are LPS, exotoxins are proteins. Incorrect.
• Option 4: Both are not made of nucleic acids (RNA/DNA); exotoxins are proteins, endotoxins are LPS. Incorrect.

Answer:

A. Endotoxins are lipopolysaccharides and thus structurally integral to the bacterium, whereas exotoxins are proteins that are secreted by living bacteria.