18 Questions
What is the composition of a G protein?
α, β, γ
In the unstimulated state, the α subunit of a G protein is bound to:
GDP
What happens to the GTP-bound α subunit of a G protein when activated by a ligand-bound receptor?
It dissociates from the βγ dimer
Which enzyme is activated by cAMP produced in response to GPCR activation?
Protein Kinase A (PKA)
What is the cellular response to activation of the β2 Adrenergic Receptor?
Modulation of gene transcription
What characterizes Enzyme-Linked Receptors?
Integral membrane proteins with a single transmembrane domain
Which of the following receptors are directly coupled to ion channels, allowing for rapid electrical signal transduction?
Ion channel-coupled receptors
Which type of receptor initiates signaling cascades involving second messengers like cAMP, cGMP, and PIP3?
G protein-coupled receptors
Which of the following ligands typically binds to G protein-coupled receptors?
Adrenaline
Which type of receptor is directly involved in the regulation of gene expression?
Intracellular steroid receptors
Which of the following signaling molecules can directly cross the plasma membrane due to their hydrophobic nature?
Steroid hormones
Which type of receptor is typically associated with tyrosine kinase activity and involved in the regulation of cell growth and differentiation?
Enzyme-linked receptors (catalytic receptors)
Which of the following statements about G-protein-coupled receptors (GPCRs) is correct?
GPCRs share a common structure with seven transmembrane domains and interact with trimeric G proteins.
What is the primary role of the trimeric G protein in the GPCR signaling pathway?
To transfer the signal from the activated GPCR to downstream effector proteins.
Which of the following is NOT an example of a ligand that can activate GPCRs?
Protons (H+ ions)
In the context of ion-channel-coupled receptors, what is the primary function of acetylcholine (Ach) at the neuromuscular junction?
To open ligand-gated Na$^+$ channels in the muscle cell membrane, leading to depolarization.
What is the role of Ca$^{2+}$ ions in the process of muscle contraction triggered by ion-channel-coupled receptors?
Ca$^{2+}$ ions are released from the sarcoplasmic reticulum into the cytosol, leading to contraction of myofibrils.
Which of the following statements about the signaling mechanisms of GPCRs and ion-channel-coupled receptors is correct?
GPCRs activate G proteins, while ion-channel-coupled receptors directly open ion channels.
Test your knowledge on intracellular signalling events mediated by second messengers and hydrophobic molecules that bind to intracellular receptors. Learn about the role of ligand-receptor binding in signal transduction pathways.
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