Whereas the Cholera Toxin ADP-Ribosylates the α Subunit of Stimulatory

question 16

Multiple Choice

Whereas the cholera toxin ADP-ribosylates the α subunit of stimulatory G protein (Gs) , thereby blocking GTP hydrolysis, pertussis toxin ADP-ribosylates the α subunit of inhibitory G protein (Gᵢ) and prevents interaction with the receptor. What is the effect of these toxins on the concentration of intracellular cAMP?

• A) Cholera toxin tends to increase cAMP concentration, whereas pertussis toxin tends to decrease cAMP concentration.
• B) Cholera toxin tends to decrease cAMP concentration, whereas pertussis toxin tends to increase cAMP concentration.
• C) They both tend to increase cAMP concentration.
• D) They both tend to decrease cAMP concentration.

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Definitions:

Apical Meristem

An area of dividing tissue, located at the tip of a shoot or root, that gives rise to primary tissues; apical meristems cause an increase in the length of the plant body. Compare with lateral meristems.

Lateral Meristem

A type of meristem or plant tissue that allows for growth in thickness or girth in a maturing plant.

Vascular Cambium

A lateral meristem that produces secondary xylem (wood) and secondary phloem (inner bark). Compare with cork cambium.

Epidermal Outgrowths

Structures like hair, feathers, or scales that develop from the epidermis, the outer layer of skin, in various organisms.