50 Questions
Which of the following is NOT a general model of intracellular signaling discussed in the text?
Ionic and gaseous lipids
What is the key function of receptors in the cell membrane?
Transforming extracellular signals into intracellular signals
Where do some 2nd messengers accumulate in the cell?
In the cytoplasm
Which of the following is NOT a function of the cell membrane in intracellular signaling?
Detecting extracellular signals
What happens in an inactive intracellular signaling system?
No extracellular signal is present
What happens in an active intracellular signaling system?
The 1st messenger becomes active
According to the text, where can more detailed explorations of cell biology be found?
In the Molecular Biology of the Cell textbook
Which enzyme is responsible for the conversion of ATP to cAMP?
Adenylyl cyclase
Which enzyme is responsible for the conversion of cAMP to 5'-AMP?
Phosphodiesterase
Which G-protein mechanism stimulates adenylyl cyclase and increases cAMP production?
Gs
Which G-protein mechanism inhibits adenylyl cyclase and decreases cAMP production?
Gi
What is the role of IP3 in the Gq GPCR signaling pathway?
It activates calcium release channel
What is the function of calmodulin in the Gq GPCR signaling pathway?
It binds to calcium and activates effectors
What is the unique feature of the Gq GPCR signaling pathway compared to other G-protein mechanisms?
It uses IP3 and DAG as second messenger systems
Which of the following is true about G-protein coupled receptors (GPCRs)?
GPCRs have three protein subunits: alpha, beta, and gamma
What happens when a ligand binds to a receptor associated with a Gs G-protein?
Gs releases GDP and binds GTP at the alpha subunit
What is the role of adenylyl cyclase in GPCR signaling?
Adenylyl cyclase converts ATP to cAMP
What happens when cAMP binds to protein kinase A (PKA)?
PKA binds to inhibitors, allowing the active parts of PKA to work
What happens when the alpha subunit of a G-protein hydrolyzes GTP?
The alpha subunit becomes inactivated
What is the role of the beta-gamma subunit in GPCR signaling?
The beta-gamma subunit detaches from the G-protein
What is the main function of GPCRs in intracellular signaling?
To bind to and activate second messengers
Which molecule can modulate the activity of many other effectors?
PKC
What is the Nernst potential for K+?
-90 mV
What is the effect of opening a channel that allows sodium to enter the cell?
The membrane becomes more inside-positive (depolarization)
What is the effect of opening a channel that allows more potassium to leave the cell?
The membrane becomes more inside-negative (hyperpolarization)
What is the effect of opening a channel that allows calcium to enter the cytosol?
Binding to calmodulin
What is the cytosolic calcium concentration compared to the extracellular calcium concentration at rest?
Almost 10,000 times lower
What is the role of Gi-α inactivating adenylyl cyclase?
Downregulating the activity of Gs
What is the role of Gi-βγ?
Opening a K+ channel
What is the role of the Na+/K+-ATPase and K+ channels in the cell membrane?
Maintaining an inside-negative membrane potential
Which class of receptors has intrinsic enzyme activity?
Receptor Tyrosine Kinases (RTKs)
What happens when a ligand binds to a receptor associated with a RTK?
The receptor dimerizes and activates a tyrosine kinase within the receptor
What is the main function of RTKs in intracellular signaling?
To phosphorylate proteins
Which signaling pathway involves the activation of phospholipase C?
Gq GPCR signaling pathway
What is the role of Ras in the Ras cascade signaling pathway?
To activate Raf
Which ligand is NOT an example of a ligand that binds to RTKs?
Acetylcholine
What happens when a ligand binds to a receptor monomer associated with an RTK?
The receptor dimerizes and each half phosphorylates the tyrosine residues on the other half
Which G-protein mechanism inhibits adenylyl cyclase and decreases cAMP production?
Gi
What is the role of the beta-gamma subunit in GPCR signaling?
To activate phospholipase C
What is the effect of opening a channel that allows calcium to enter the cytosol?
Increase in cytosolic calcium concentration
Which of the following is the key pathway for many growth factors?
Ras-Raf-MAP kinase pathway
What is the role of PIP3 in the PI3K-Akt pathway?
It accumulates and forms lipid rafts in the membrane
What is the function of Akt in the PI3K-Akt pathway?
It influences a range of intracellular targets
Which molecule is produced from GTP by guanylyl cyclase in the nitric oxide-mediated pathway?
cGMP
What is the effect of elevated cytosolic cGMP in the nitric oxide-mediated pathway?
It activates a protein kinase (usually PKG)
What is the role of nitric oxide synthase (NOs) in the nitric oxide-mediated pathway?
It produces nitric oxide from L-arginine
Which of the following is NOT a characteristic of nitric oxide (NO)?
It has long-lasting effects
What is the role of Ras in the Ras-Raf-MAP kinase pathway?
It inactivates itself by cleaving GTP to GDP
What is the unique signaling mechanism of the PI3K-Akt pathway?
It is key to insulin signaling
What is the role of PDK1 in the PI3K-Akt pathway?
It becomes activated by PIP3
Test your knowledge on signal transduction and the role of PKA in activating signals. Learn about the release of inhibitors and the movement of calcium in this quiz based on molecular biology concepts.
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