Chapter 15 (part 2)

Which of the following correctly describes exotoxins?

• They are released only when Gram-negative bacteria die and their cell walls break apart.

• They are produced by both Gram-positive and Gram-negative bacteria and secreted from live cells during normal growth and metabolism.

• They are found only in the outer membrane of Gram-negative bacteria.

• They are part of the bacterial cell wall and not secreted into the environment.

Which of the following best describes the potency and behavior of exotoxins?

• They are weak toxins that require large doses to cause harm and remain localized at the infection site.

• They are extremely toxic in very small amounts and, because they are soluble, can easily spread throughout the body.

• They are only harmful when bacteria die and release them.

• They are non-toxic and primarily serve as bacterial nutrients.

What is true about the effects of exotoxins on the body?

• Exotoxins have general, nonspecific effects on all body tissues.

• Each exotoxin targets specific types of body cells, causing particular symptoms based on which cells are affected.

• Exotoxins only affect cells of the immune system.

• Exotoxins cause symptoms that are the same for all bacterial infections.

How are the genes for many exotoxins typically carried and transferred between bacteria?

• They are located only on the bacterial chromosome and cannot be transferred.

• They are encoded on plasmids or bacteriophages, allowing them to be transferred between bacteria.

• They are inherited only through bacterial spores.

• They are found in the bacterial cell wall and spread by contact.

Which of the following diseases is caused by exotoxins?

• Botulism and staphylococcal food poisoning

• Salmonellosis and typhoid fever

• Tuberculosis and leprosy

• Lyme disease and syphilis

What are antitoxins?

• Enzymes that help bacteria produce more exotoxins

• Antibiotics that destroy bacterial toxins directly

• Antibodies produced by the body that neutralize exotoxins

• Chemicals added to vaccines to increase their strength

What are toxoids and how are they used?

• Active toxins used to increase immunity through infection

• Inactivated toxins used in vaccines, such as the DTaP vaccine for diphtheria, tetanus, and pertussis

• Antibiotics that destroy bacterial toxins before they spread

• Toxins that have become more potent after exposure to heat or chemicals

Which of the following correctly describes A-B toxins?

• They contain two parts: the B subunit binds to the host cell, and the A subunit enters the cell and interferes with normal functions such as protein synthesis.

• They consist of a single subunit that disrupts the plasma membrane of host cells.

• They are toxins that directly destroy DNA in the nucleus.

• They cause damage only when the bacteria die and release endotoxins.

Which of the following is an example of an A-B toxin?

• Diphtheria toxin

• Botulinum neurotoxin

• Tetanospasmin

• Vibrio cholerae enterotoxin

• All of the above

What is the main action of membrane-disrupting toxins?

• They inhibit protein synthesis by interfering with ribosomes.

• They kill host cells by damaging or lysing the plasma membrane.

• They overactivate the immune system and cause cytokine storms.

• They block neurotransmitter release at synapses.