Please select characteristics exhibited by endotoxins, but not exhibited by exotoxins.
Check All That Apply
a. composed of lipopolysaccharide
b. require very small doses to cause toxic effects
c. released only by gram-negative bacteria
d. heat-stable
e. have very specific targets
f. fever-inducing
Please select the body sites that remain free of normal microbiota.
Check All That Apply
a. large intestine
b. kidneys
c. brain
d. uterus
e. vagina
f. bones
The Correct Answer and Explanation is :
Characteristics of Endotoxins (but not Exotoxins):
- a. composed of lipopolysaccharide: Endotoxins are composed of lipopolysaccharides (LPS), which are a major component of the outer membrane of Gram-negative bacteria. Exotoxins, on the other hand, are proteins secreted by both Gram-positive and Gram-negative bacteria.
- c. released only by gram-negative bacteria: Endotoxins are only found in the cell walls of Gram-negative bacteria, as they are a component of the outer membrane. Exotoxins can be produced by both Gram-positive and Gram-negative bacteria.
- d. heat-stable: Endotoxins are typically heat-stable, meaning they can withstand high temperatures without losing their toxic properties. Exotoxins, however, are often heat-labile and can be inactivated by heat.
- f. fever-inducing: Endotoxins are known to trigger fever (pyrogenic response) when they enter the body. This occurs due to the stimulation of the immune system and the release of cytokines. Exotoxins generally do not induce fever.
Body Sites That Remain Free of Normal Microbiota:
- b. kidneys: The kidneys are typically sterile and free from normal microbiota. Microbial presence in the kidneys is often associated with infections.
- c. brain: The brain, along with the central nervous system, is normally free of microbiota. The blood-brain barrier helps to protect the brain from microbial colonization.
- d. uterus: The uterus is generally considered sterile during pregnancy, but it can be colonized with microbes during childbirth or infections.
- f. bones: Bones, like the brain and kidneys, are typically sterile and do not contain normal microbiota. Bone infections (osteomyelitis) are often due to external bacterial introductions.
Explanations:
Endotoxins, which are part of the outer membrane of Gram-negative bacteria, differ significantly from exotoxins, which are proteins secreted by bacteria. The heat-stability of endotoxins and their ability to induce fever are important characteristics that help in distinguishing them from exotoxins, which tend to be protein-based and may cause more specific effects, such as targeting specific cells or tissues.
Regarding normal microbiota, the kidneys, brain, and bones are sites that remain free from typical microbial populations under normal, healthy conditions. These organs have defenses in place (such as the blood-brain barrier or sterile environments) that prevent the colonization of bacteria or other microorganisms. Conversely, organs like the large intestine, vagina, and uterus (in certain conditions) may host various microbes.