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WorksheetsSignaling
Total questions: 26
Worksheet time: 13mins
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
What is the primary action of protein kinase A (PKA)?
Converts cAMP to AMP
Opens sodium ion channels
Phosphorylates target proteins on serine/threonine residues
Activates PI3K
Which of the following statements is TRUE about steroid hormone signaling?
It involves activation of membrane-bound ion channels
Steroid receptors are found on the cell surface
Steroid-receptor complexes often act as transcription factors
Steroid hormones increase intracellular calcium via PLC
Which of the following best describes the JAK-STAT signaling pathway?
GPCR-mediated cAMP pathway
Ionotropic receptor pathway
Cytokine receptor pathway that activates gene transcription
Receptor tyrosine kinase pathway that increases cGMP
Which signaling event is associated with nitric oxide (NO)?
Activation of adenylate cyclase
Stimulation of phospholipase C
Activation of soluble guanylate cyclase to increase cGMP
Inhibition of Ca²⁺ release from the ER
Which kinase is activated as a result of PIP₃ formation by PI3-kinase (PI3K)?
PKA
PKG
PKB (Akt)
CaM-kinase
What happens when a receptor undergoes downregulation?
Receptor activity is enhanced
The receptor is dephosphorylated
The receptor is internalized or degraded to reduce responsiveness
The receptor is cleaved to activate it
Which of the following is a shared feature of all kinase signaling cascades?
Ligand-gated ion channels
Activation of phosphodiesterases
Phosphorylation of proteins on amino acid residues
Direct binding to DNA sequences
Which of the following correctly compares Gαs and Gαi?
Both increase cAMP levels
Gαs activates adenylate cyclase, Gαi inhibits it
Gαi stimulates phospholipase C, Gαs inhibits it
Gαs and Gαi both stimulate PKA
What is the role of DAG in the IP₃/DAG pathway?
Increases intracellular calcium levels directly
Activates protein kinase C (PKC)
Opens calcium channels on the ER
Binds to PKA to activate transcription
Which kinase is activated by calcium-calmodulin complexes?
PKB
PKC
CaM-Kinase
JAK
Which receptor is coupled with the Gαq protein?
β2-adrenergic receptor
α1-adrenergic receptor
Glucagon receptor
D2 dopamine receptor
What effect would a drug that mimics β-blockers have on heart cells?
Increases Gαs activity and raises cAMP
Inhibits β-adrenergic receptors and lowers cAMP
Stimulates IP₃ and DAG pathways
Enhances NO release and increases PKG activation
What is the biological significance of signal amplification in a G-protein signaling cascade?
It prevents overstimulation by degrading receptors
It ensures only one molecule of ATP is used per response
It allows a single ligand-receptor interaction to produce a large cellular response
It activates the immune system
In which of the following scenarios would you expect cGMP levels to rise significantly?
Activation of β-adrenergic receptors
Vasodilation stimulated by nitric oxide
Glucagon binding to its receptor
Phospholipase C activation by Gαq
What effect does phosphorylation of a receptor often have in feedback regulation?
Increases receptor synthesis
Enhances ligand binding
Leads to receptor desensitization or internalization
Stimulates G-protein activation
Which of the following enzymes directly converts ATP to cAMP?
Guanylate cyclase
PI3-kinase
Adenylate cyclase
Phosphodiesterase
