Signal transduction pathways Practice Questions

Question 1

Which receptor type mediates the slow phase of synaptic transmission in autonomic ganglia?

Accepted Answer

Muscarinic (M1)

Answer

Muscarinic (M3)

Answer

Muscarinic (M2)

Answer

Nicotinic (N2)

Question 2

A 21-year-old man presents to the office for a follow-up visit. He was recently diagnosed with type 1 diabetes mellitus after being hospitalized for diabetic ketoacidosis following a respiratory infection. He is here today to discuss treatment options available for his condition. The doctor mentions a recent study in which researchers have developed a new version of the insulin pump that appears efficacious in type 1 diabetics. They are currently comparing it to insulin injection therapy. This new pump is not yet available, but it looks very promising. At what stage of clinical trials is this current treatment most likely at?

Accepted Answer

Phase 3

Answer

Phase 0

Answer

Phase 2

Answer

Phase 1

Answer

Phase 4

Question 3

A 55-year-old man comes to the physician with a 3-month history of headache, periodic loss of vision, and easy bruising. Physical examination shows splenomegaly. His hemoglobin concentration is 13.8 g/dL, leukocyte count is 8000/mm3, and platelet count is 995,000/mm3. Bone marrow biopsy shows markedly increased megakaryocytes with hyperlobulated nuclei. Genetic analysis shows upregulation of the JAK-STAT genes. The pathway encoded by these genes is also physiologically responsible for signal transmission of which of the following hormones?

Accepted Answer

Prolactin

Answer

Oxytocin

Answer

Adrenocorticotropic hormone

Answer

Cortisol

Answer

Insulin

Question 4

A group of scientists is studying the mechanism of action of various pancreatic hormones in rats. The scientists studied hormone A, which is secreted by the β-cells of the pancreas, and found that hormone A binds to a complex dimeric receptor on the cell membrane and exerts its effects via phosphorylation and subsequent downstream signaling that includes dephosphorylation of different intracellular proteins. Now they are studying hormone B, which is secreted by the α-cells and antagonizes the actions of hormone A. Which 2nd messenger system would hormone B utilize to exert its cellular effects?

Accepted Answer

Adenylyl cyclase-cyclic AMP

Answer

Direct cytoplasmic receptor binding

Answer

Phospholipase C

Answer

Tyrosine kinase

Answer

Direct nuclear receptor binding

Question 5

A 69-year-old woman comes to the clinic for an annual well exam. She reports no significant changes to her health except for an arm fracture 3 weeks ago while she was lifting some heavy bags. Her diabetes is well controlled with metformin. She reports some vaginal dryness that she manages with adequate lubrication. She denies any weight changes, fevers, chills, palpitations, nausea/vomiting, incontinence, or bowel changes. A dual-energy X-ray absorptiometry (DEXA) scan was done and demonstrated a T-score of -2.7. She was subsequently prescribed a selective estrogen receptor modulator, in addition to vitamin and weight-bearing exercises, for the management of her symptoms. What is the mechanism of action of the prescribed medication?

Accepted Answer

Estrogen antagonist in breast and agonist in bone

Answer

Estrogen antagonist in cervix and agonist in bone

Answer

Estrogen agonist in bone and breast

Answer

Partial estrogen agonist in endometrium and bone

Answer

Partial estrogen agonist in bone and antagonist in cervix

Question 6

You are currently employed as a clinical researcher working on clinical trials of a new drug to be used for the treatment of Parkinson's disease. Currently, you have already determined the safe clinical dose of the drug in a healthy patient. You are in the phase of drug development where the drug is studied in patients with the target disease to determine its efficacy. Which of the following phases is this new drug currently in?

Accepted Answer

Phase 2

Answer

Phase 4

Answer

Phase 1

Answer

Phase 0

Answer

Phase 3

Question 7

A researcher is currently working on developing new cholinergic receptor agonist drugs. He has formulated 2 new drugs: drug A, which is a selective muscarinic receptor agonist and has equal affinity for M1, M2, M3, M4, and M5 muscarinic receptors, and drug B, which is a selective nicotinic receptor agonist and has equal affinity for NN and NM receptors. The chemical structure and mechanisms of action of both drugs mimic acetylcholine. However, drug A does not have any nicotinic receptor activity and drug B does not have any muscarinic receptor activity. Which of the following statements is most likely correct regarding these new drugs?

Accepted Answer

Drug B acts by stimulating a receptor which is composed of 5 subunits

Answer

Drug B may produce some of its effects by activating the IP3-DAG (inositol triphosphate-diacylglycerol) cascade

Answer

Drug A acts by causing conformational changes in ligand-gated ion channels

Answer

Drug A acts on receptors located at the neuromuscular junctions of skeletal muscle

Answer

Drug A acts by stimulating a receptor which is composed of 6 segments

Question 8

A 78-year-old man receives chemotherapy for advanced hepatocellular carcinoma. Despite appropriate therapy, he dies 4 months later. Histopathological examination of the cancer cells shows the presence of a transmembrane efflux pump protein that is known to cause decreased intracellular concentrations of chemotherapeutic drugs. Which of the following best describes this membrane protein?

Accepted Answer

P-glycoprotein

Answer

G protein

Answer

Cadherin

Answer

Tyrosine receptor

Answer

Channel protein

Question 9

A 24-year-old woman presents to the emergency department with abdominal pain that started while she was at the gym. The patient competes as a power lifter and states that her pain started after one of her heavier lifts. The patient has no significant past medical history and is currently taking a multivitamin and oral contraceptive pills. She smokes cigarettes and drinks alcohol regularly and is currently sexually active with multiple partners. Her temperature is 99°F (37.2°C), blood pressure is 85/55 mmHg, pulse is 125/min, respirations are 18/min, and oxygen saturation is 99% on room air. Physical exam is notable for right upper quadrant abdominal tenderness, acne, and muscle hypertrophy. Right upper quadrant ultrasound demonstrates a solitary heterogeneous mass. Which of the following other findings is most likely to be found in this patient?

Accepted Answer

Increased LDL and decreased HDL

Answer

Elevated viral core antigen

Answer

Elevated alpha fetoprotein

Answer

Increased pigmentation in flexural areas

Answer

Prolonged PT and PTT

Question 10

A research team discovers a novel bacterial toxin that causes severe hypotension in infected patients. In vitro studies show the toxin ADP-ribosylates a specific amino acid on Gq alpha subunits, preventing their activation by GPCRs. Patients develop hypotension despite elevated levels of vasopressin, angiotensin II, and endothelin-1. Synthesize the pathophysiological mechanism explaining why multiple vasopressor hormones fail to maintain blood pressure in these patients.

Accepted Answer

ADP-ribosylation of Gq prevents PLC activation, blocking IP3-mediated calcium release and vascular smooth muscle contraction

Answer

The toxin depletes intracellular ATP preventing myosin-actin interaction

Answer

The toxin prevents receptor binding of vasopressor hormones through allosteric inhibition

Answer

ADP-ribosylation increases cAMP levels causing smooth muscle relaxation

Answer

The toxin activates Gi proteins causing excessive vasodilation that overwhelms vasoconstrictor signals

Signal transduction pathways

Study Resources

Lessons

Questions

Flashcards

Lessons

G-protein coupled receptors

Tyrosine kinase receptors

Second messenger systems (cAMP, cGMP, Ca2+)

MAP kinase pathways

JAK-STAT pathway

PI3K-Akt pathway

Nuclear receptor signaling

WNT signaling pathway

Notch signaling pathway

Hedgehog signaling pathway

TGF-β/SMAD signaling

NF-κB signaling

Dysregulation in disease states

Pharmacological targeting of signaling pathways

Practice Questions

Flashcards

About Signal transduction pathways for USMLE

Lessons in Signal transduction pathways

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