17 Questions
What is the role of the α subunit of a G protein in signal transduction?
The α subunit splits GTP into GDP and Pi, acting as a switch.
Which of the two most common effector enzymes for G protein-coupled receptors is responsible for the production of the second messenger cyclic AMP (cAMP)?
Adenylyl cyclase
What is the role of inositol trisphosphate (IP3) as a second messenger?
It enters the cytoplasm and binds to a calcium channel on the endoplasmic reticulum, causing the release of calcium into the cytosol
What is the role of cyclic AMP (cAMP) in the cAMP signaling pathway?
cAMP activates protein kinase A (PKA), which then phosphorylates other intracellular proteins.
Which of the following is a function of calcium as a second messenger?
It triggers the release of secretory vesicles through exocytosis
What is the role of the G protein-coupled adenylyl cyclase-cAMP system?
It produces the second messenger cAMP, which then changes the activities of the cell
Which of the following is not a step in the general sequence of events in the cAMP signaling pathway?
The receptor directly activates adenylyl cyclase to produce cAMP.
What is the mechanism of activation of the phospholipase C pathway?
Binding of a ligand to a G protein-coupled receptor activates phospholipase C, which then cleaves phosphatidylinositol bisphosphate (PIP2) into diacylglycerol (DAG) and inositol trisphosphate (IP3)
What is the second most common effector enzyme for G protein-coupled receptors?
Phospholipase C
What are the two types of intracellular (nuclear) receptors described in the text?
Inactive receptors located in the cytosol that move into the nucleus after binding their ligand, and active receptors located in the nucleus
What are the two main second messengers produced by the activation of phospholipase C in the phosphoinositide signaling pathway?
Inositol trisphosphate (IP3) and diacylglycerol (DAG)
Which of the following is a key step in the G protein-coupled receptor signaling pathway?
Activation of adenylyl cyclase leading to increased cAMP levels
What is the primary function of phospholipase C in cell signaling?
Cleavage of phosphatidylinositol 4,5-bisphosphate (PIP2) to produce IP3 and DAG
Which of the following is a second messenger produced by the activation of phospholipase C?
IP3
What is the primary function of protein kinases in cell signaling pathways?
Phosphorylation of target proteins to alter their activity
Which of the following receptors is known to activate the phospholipase C signaling pathway?
Acetylcholine receptor (muscarinic type)
What is the primary mechanism for terminating the signal initiated by the adenylyl cyclase-cAMP pathway?
Degradation of cAMP by phosphodiesterases
Study Notes
- Inactive receptors can be found in the cell nucleus and are activated by ligands like thyroid receptors, leading to altered gene transcription rates.
- Receptor activity can be terminated by removing chemical messengers, degrading them, or endocytosis of the receptor-ligand complex.
- Second messengers like cAMP, calcium, and effector proteins play crucial roles in signal transduction pathways.
- G-protein-coupled receptors can activate ion channels or enzymes in the plasma membrane, with examples like muscarinic ACh receptors requiring G-proteins for action.
- Adenylyl cyclase is an important enzyme in the cAMP pathway, converting ATP to cAMP, which then activates protein kinase A (PKA) to phosphorylate other proteins in the signal cascade.
Test your knowledge on cell signaling pathways including G protein-coupled adenylyl cyclase-cAMP system, protein kinase activation, and activation of phospholipase C. Identify key components like adenylyl cyclase, cAMP, phospholipase C, Diacylglycerol (DAG), and Inositol Trisphosphate (IP3).
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