Site MapHelpFeedbackA-B Exotoxins (Diphtheria Exotoxin)
A-B Exotoxins (Diphtheria Exotoxin)

Why do bacteria produce toxins? Bacteria that cause illness are termed pathogenic. Pathogenic bacteria cause most of their negative effects through the production of toxins. Endotoxins are components of the cellular membranes of some bacteria. Exotoxins are chemical produced by bacteria that are released into their environment. Bacterial toxins have a wide range of effects on their hosts. The function of toxins, in other words, the benefit the bacteria get from the toxins, is often unclear. In some cases toxins damage the host’s immune system allowing bacterial populations in the body to grow. However many toxins have effects that have no obvious benefit to the bacteria. In fact, some my hinder bacterial growth by killing the host very quickly.

View the animation below, then complete the quiz to test your knowledge of the concept.

1In A-B toxins
A)A is the toxic part
B)B is the toxic part
C)both A and B are toxic
D)neither A or B are toxic
E)B is toxic only after A has allowed it to enter the cell

2How does the toxin enter the cell?
A)after B binds to host cell receptors, A enters the host cell alone by endocytosis
B)after B binds to host cell receptors, both A and B enter the host cell by endocytosis
C)after A binds to host cell receptors, A enters the host cell by endocytosis
D)after both A and B bind to host cell receptors, both A and B enter by endocytosis

3After the A-B toxin enters the cell
A)an alkaline pH causes A and B to separate
B)A is removed by exocytosis
C)B is removed by exocytosis
D)B causes toxicity
E)both A and B prevent protein synthesis

4In Corynebacterium diphtheriae, the A toxin produced carries out the transfer of ADP-ribose to elongation factor 2, inhibiting protein synthesis.

5All A toxins work the same way.

Animation Quiz SiteOnline Learning Center

Home > Biology 1 > Chapter 27 > A-B Exotoxins (Diphtheria Exotoxin)