$$G\_s + GTP \rightarrow G\_s^* \rightarrow \text{Adenylyl Cyclase Activation}$$

Question 1

Which of the following best describes the effect of cholera toxin on GPCR signaling?

Accepted Answer

It permanently activates the G\_s protein, increasing cAMP production.

Question 2

Pertussis toxin affects GPCR signaling by:

Accepted Answer

Inhibiting the G\_i protein, preventing inhibition of adenylyl cyclase.

Question 3

If both cholera and pertussis toxins are present in a cell, what is the expected effect on cAMP concentration?

Accepted Answer

cAMP concentration would increase significantly.

Question 4

Which equation correctly represents the activation of adenylyl cyclase by G\_s protein?

Accepted Answer

$$G\_s + GTP ightarrow G\_s^* ightarrow 	ext{Adenylyl Cyclase Activation}$$

Question 5

A patient with cholera infection is likely to experience which of the following due to increased cAMP?

Accepted Answer

Increased secretion of water and electrolytes in the intestines.

Question 6

Pertussis toxin catalyzes the addition of ADP-ribose to G\_i, which locks it in the GDP-bound state. What is the consequence?

Accepted Answer

G\_i cannot inhibit adenylyl cyclase, leading to increased cAMP.

Question 7

Which of the following is a real-life example of an antagonist acting at a receptor?

Accepted Answer

Caffeine blocking adenosine receptors, preventing drowsiness.

Question 8

Which statement best describes the difference between an agonist and an antagonist?

Accepted Answer

An agonist binds and activates a receptor; an antagonist binds and inhibits the receptor.

Question 9

If pertussis toxin is present, what would be the effect on glycogen production in the liver?

Accepted Answer

It would further decrease glycogen production.

Question 10

Which of the following best explains why cholera and pertussis toxins both lead to increased cAMP?

Accepted Answer

Cholera activates G\_s, while pertussis inhibits G\_i, both removing inhibition on adenylyl cyclase.

Question 11

Which of the following is NOT a mechanism by which drugs and toxins affect GPCR signaling?

Accepted Answer

Binding and inhibiting secondary messengers.

Question 12

Adenosine normally causes drowsiness by activating its receptor. Caffeine acts as an antagonist. What is the effect?

Accepted Answer

Caffeine blocks adenosine receptors, reducing drowsiness.

Question 13

Which of the following equations represents the effect of cholera toxin on G\_s protein?

Accepted Answer

$$	ext{Cholera Toxin} + G\_s ightarrow G\_s^* ightarrow \uparrow 	ext{cAMP}$$

Question 14

Which of the following is a plausible effect of increased cAMP in intestinal cells?

Accepted Answer

Enhanced water and electrolyte secretion, leading to diarrhea.

Question 15

Which of the following best describes the role of G\_i protein in GPCR signaling?

Accepted Answer

G\_i inhibits adenylyl cyclase, decreasing cAMP production.

Drugs & Toxins Affecting GPCR Signaling and Signal Transduction

Study Guide - Practice Questions