Signaling

Which of the following best describes the function of a second messenger?

• It directly binds to receptors on the cell membrane

• It is a hormone that circulates in the blood

• It is generated inside the cell following receptor activation and mediates intracellular effects

• It degrades neurotransmitters in the synaptic cleft

Which type of signaling is primarily associated with neurotransmitters?

• Endocrine

• Paracrine

• Autocrine

• Exocrine

What is the function of cAMP phosphodiesterase?

• Converts ATP to cAMP

• Converts cAMP to AMP

• Activates PKA

• Inhibits adenylate cyclase

Which second messenger system is primarily responsible for activating Protein Kinase A (PKA)?

• cAMP

• IP₃

• DAG

• cGMP

Which of the following is a correct match between receptor location and hormone type?

• Membrane receptors – Steroid hormones

• Cytoplasmic receptors – Protein hormones

• Nuclear receptors – Steroid hormones

• Membrane receptors – Lipophilic hormones

What is the expected biochemical result of a pertussis toxin exposure?

• Decreased cAMP due to Gαs inhibition

• Increased cAMP due to Gαi inhibition

• Increased DAG due to PLC activation

• Decreased NO synthesis

Which of the following best explains how β-blockers lower heart rate?

• They block Gαi and increase cAMP

• They activate Gαq to inhibit PKA

• Reducing Gαs activation and decreasing cAMP

• They stimulate PIP₂ cleavage by PLC

Which toxin prevents the hydrolysis of GTP by Gαs, leading to prolonged activation of adenylate cyclase?

• Pertussis toxin

• Botulinum toxin

• Cholera toxin

• Tetanus toxin

Which of the following is an example of a second messenger?

• Insulin

• GABA

• cAMP

• Dopamine

Activation of Gαs leads to which of the following outcomes?

• Inhibition of adenylate cyclase

• Activation of phospholipase C

• Activation of adenylate cyclase and increased cAMP

• Inhibition of PKA