After specific binding of an agonist that inhibits adenylyl cyclase activity via a G protein-linked receptor,
A. Gi binds GDP in place of GTP.
B. Gs binds GDP in place of GTP.
C. Gi binds GTP in place of GDP.
D. Gs binds GTP in place of GDP.
E. Gi binds GDP and Gs binds GTP.
Answer
An agonist that stimulates adenylate cyclase activity via a G protein-linked receptor
A. promotes the replacement of Gs-bound GDP by cAMP.
B. promotes the replacement of Gi-bound GDP by GTP.
C. promotes the replacement of Gi-bound GTP by GDP.
D. promotes the replacement of Gs-bound GDP by GTP.
E. promotes the replacement of Gs-bound GTP by GDP.
Answer
Which one of the following events occurs in order to stimulate adenylyl cyclase activity via a G protein-linked receptor?
A. Gs binds GDP
B. Gi binds GTP
C. Gs binds diacylglycerol
D. Gs binds GTP
E. Gs binds cAMP
Answer
In transduction events associated with the calcium-phosphoinositide second messenger system,
A. protein kinase C is activated by IP3 in a calmodulin-dependent manner.
B. phospholipase C diffuses through the cytosol to mobilize stored intracellular calcium.
C. diacylglycerol stimulates protein kinase C activity.
D. calcium stimulates release of stored IP3.
E. phosphodiesterase inhibits protein kinase C activity.
Answer
Once formed, cAMP acts mainly by next
A. stimulating intracellular release of stored calcium.
B. stimulating protein kinase A.
C. stimulating phosphodiesterase.
D. stimulating phospholipase C.
E. stimulating tyrosine kinases.
Answer
As a result of activation of Phospholipase C,
A. IP3 stimulates the intracellular release of stored calcium.
B. diacylglycerol stimulates protein kinase A activity.
C. protein kinase C inhibits protein kinase A.
D. Gq inhibits adenylyl cyclase activity.
E. membrane integrity is destroyed.
Answer
Which statement about G proteins is FALSE?
A. They mediate the effect of stimulation of G protein-linked receptors on generation of second messengers.
B. They contain three identical subunits.
C. They bind guanine nucleotides GTP and GDP.
D. They come in several varieties.
E. They are located in the plasma membrane.
Answer
Which statement about G proteins is FALSE?
A. They consist of five subunits.
B. They are located in the plasma membrane.
C. The alpha-subunit confers specificity.
D. They bind GDP and GTP.
E. They cycle between inactive and active states.
Answer
Which one of the following statements about the 5HT3 receptor is FALSE? The 5HT3 receptor
A. is coupled to G protein and therefore has seven transmembrane domains in its structure.
B. plays a role in the Bezold-Jarisch reflex.
C. is in the same superfamily of receptors as the nicotinic receptor.
D. plays a role in emesis.
E. is blocked by ondansetron (Zofran).
Answer
You analyze plasma disappearance curves for two new drugs. You find that the slope for the elimination phase for Drug I is much steeper than for Drug II. The y-intercept for Drug I is much greater than for Drug II. You conclude:
A. Drug I has the greater Vd; Drug II has the faster elimination rate.
B. Drug I has the greater Vd; Drug I has the faster elimination rate.
C. Drug II has the greater Vd; Drug I has the faster elimination rate.
D. Drug II has the greater Vd; Drug II has the faster elimination rate.
Answer
Which of the following drug reservoirs preferentially sequesters the tetracycline antibiotics?
A.Fat
B. Lung
C. Bone
D. Muscle
E. Serum albumin
Answer
The body reservoir that holds the largest amount of the barbiturate thiopental (Pentothal) is
A. adipose.
B. lung.
C. liver.
D. muscle.
E. serum albumin.
Answer
Which of the following properties are considered physiological variables which affect drug absorption and distribution?
A. Gastric motility
B. pH at absorption site
C. Surface area available for absorption
D. Blood flow
E. All of the above
Answer
Digoxin has an apparent volume of distribution of 700 L indicating that it is distributed
A. preferentially to plasma binding proteins, particularly albumin.
B. equally throughout all body compartments.
C. selectively into the crystal structure of large bones.
D. in a cellular reservoir such as muscle and adipose.
E. none of the above
Answer
After administration of 100 micrograms of drug X the concentration of this drug in the circulating plasma was determined to be 0.2 nanogram/ml. Given these facts which of the following statements is TRUE?
A. The apparent volume of distribution is approximately 500 L indicating that the drug is chiefly bound to plasma proteins.
B. The apparent volume of distribution is approximately 0.002 L indicating that the drug is chiefly bound to plasma proteins.
C. The apparent volume of distribution is approximately 500 L indicating that the drug is hydrophobic and preferentially distributed to muscle and/or adipose tissue reservoirs.
D. The
apparent volume of distribution 
is approximately 0.002 L indicating that the drug is hydrophobic and preferentially distributed to muscle and/or adipose tissue reservoirs.
E. The volume of distribution can not be determined without knowing the patient's weight.
Answer
A drug is administered intravenously, and a steady-state plasma concentration of 4 µg/ml is obtained. If this drug is entirely eliminated by the liver at a rate of 800 µg/min, what would be the total body clearance (CL) for this compound?
A. .2 ml/min
B. .5 ml/min
C. 20 ml/min
D. 50 ml/min
E. 200 ml/min
Answer
Mr. Juniper Berry gulps a drink of 100-proof gin at hourly intervals starting at 8 PM. He can metabolize 1 ounce of this drink per hour. His first four drinks are 3/4 ounce each, and then he triples his hourly dose. What effect will this change in dose have on his plasma levels of ethanol, which are measured hourly?
A After about four drinks at the higher dose, the plasma level will reach a new plateau.
B Plasma level of ethanol will not change in response to the higher dose but toxic metabolite levels will rise exponentially.
C After increasing the dose, hourly plasma level will increase continually.
D Plasma level will decline gradually due to induction of metabolic enzymes.
E None of the above.
Answer
The major symptom of pheochromocytoma
, a rare tumor, can be treated by
A. phenylephrine.
B. propranolol.
C. phenoxybenzamine.
D. albuterol.
E. ephedrine.
Answer
An example of an irreversible (noncompetitive) antagonist is
A. phenoxybenzamine.
B. timolol.
C. ephedrine.
D. reserpine.
E. "C" and "D" are correct.
Answer
Which of the following is NOT true for active transport?
A. It is highly selective.
B. It is competitively inhibited by congeners.
C. It is non-saturable.
D. It allows for movement against the concentration gradient.
E. It has a strict energy requirement.
Answer
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In the presence of a competitive antagonist, the dose-response curve of an agonist is shifted
A. to the right with no loss of efficacy.
B. to the right with a loss of efficacy.
C. to the left with no loss of efficacy.
D. to the left with a loss of efficacy.
E. eliminated as no agonist response may be elicited.
Answer
A partial agonist may be best described as
A. producing a different class of 2nd messenger response than a full agonist.
B. producing different classes of 2nd messenger responses in different tissues.
C. an agonist with low affinity.
D. an agonist highly prone to metabolic inactivation.
E. an agonist with low efficacy.
Answer
An agonist stimulates a receptor coupled to the calcium-phosphoinositide second messenger system. What happens?
A. Increase in influx of extracellular calcium and stimulation of adenylate cyclase.
B. Efflux of intracellular calcium and stimulation of phosphodiesterase.
C. Liberation of stored intracellular calcium and stimulation of protein kinase C.
D. Sequestration of intracellular calcium and inhibition of phosholipase C.
E. Increased phosphorylation of DAG and opening of sodium channels.
Answer
Which statement is INCORRECT?
A. A pure antagonist has high affinity / no efficacy.
B. A partial agonist has low affinity / high efficacy.
C. Competitive antagonism can be overcome by increasing the dose of agonist.
D. Spare receptors are not accounted for in classical receptor occupancy theory.
E. A full agonist has high affinity / high efficacy.
Answer
I
n the presence of a competitive antagonist, which of the following statements about the agonist dose-response curve is CORRECT?
A. shifted to the left along x-axis with no change in maximum response.
B. shifted to the right along x-axis with no change in maximum response.
C. shifted to the left along x-axis with a decrease in maximum response.
D. shifted to the right along x-axis with a decrease in maximum response.
E. none of the above.
Answer
Which statement best describes an original premise of classical receptor occupancy theory?
A. the magnitude of effect is directly proportional to the fraction of drug receptors occupied.
B. drug responses represent the result of a series of post-receptor amplification events.
C. the maximum effect may occur without all drug receptors being occupied.
D. RT (total receptor concentration) changes with dose of the drug.
E. All of the above apply equally well to the theory.
Answer
Which of the following statements regarding drug-receptor interactions is CORRECT?
A. A pure antagonist has high affinity / no efficacy.
B. A pure agonist has low affinity / high efficacy.
C. A partial agonist has low affinity / low efficacy.
D. Competitive antagonism is irreversible.
E. Spare receptors are accounted for in classical receptor occupancy theory.
Answer
Which of the following statements about receptors is NOT true?
A. When agonists are bound to them, adrenergic alpha1 receptors increase production of IP3 and DAG.
B. The M3 muscarinic receptor are found on exocrine glands innervated by the parasympathetic nervous system.
C. The NM receptor is cholinergic, opens Na+, K+ channels in response to acetylcholine and found at the ganglia of both the sympathetic and parasympathetic nervous systems.
D. D1 receptors, in response to agonists, stimulate adenylyl cyclase.
E. Beta3 adrenoceptors are found in adipocytes (fat cells) and increase the production of cAMP when stimulated.
Answer
