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Questions and Answers
What is the direct result of Nitric Oxide binding to guanylyl cyclase?
What is the direct result of Nitric Oxide binding to guanylyl cyclase?
- Formation of cyclic AMP
- Activation of protein kinase A
- Formation of cyclic GMP (correct)
- Activation of G-protein coupled receptors
How does Viagra enhance penile erection?
How does Viagra enhance penile erection?
- By activating GTP-binding proteins
- By promoting vasoconstriction
- By prolonging the NO signal through cyclic GMP (correct)
- By inhibiting cyclic GMP formation
Which signaling molecule acts as a molecular switch by switching from an inactive state to an active state upon receiving a signal?
Which signaling molecule acts as a molecular switch by switching from an inactive state to an active state upon receiving a signal?
- GTP-binding proteins (correct)
- Protein kinase A
- Cyclic AMP
- Calcium ions
What effect does an increase in cyclic GMP have on muscles?
What effect does an increase in cyclic GMP have on muscles?
Which enzyme is responsible for hydrolyzing bound GTP to GDP in GTP-binding proteins?
Which enzyme is responsible for hydrolyzing bound GTP to GDP in GTP-binding proteins?
Which of the following molecules is NOT typically associated with the cyclic AMP signaling pathway?
Which of the following molecules is NOT typically associated with the cyclic AMP signaling pathway?
Which enzyme is a common target for G-protein activation in the cyclic AMP pathway?
Which enzyme is a common target for G-protein activation in the cyclic AMP pathway?
How do some dissolved gases like Nitric Oxide activate intracellular enzymes?
How do some dissolved gases like Nitric Oxide activate intracellular enzymes?
Which second messenger is involved in triggering a rise in intracellular Ca2+?
Which second messenger is involved in triggering a rise in intracellular Ca2+?
Which intracellular event can be triggered by a rise in intracellular cyclic AMP?
Which intracellular event can be triggered by a rise in intracellular cyclic AMP?
Which of the following is NOT a common target enzyme for G-protein activation?
Which of the following is NOT a common target enzyme for G-protein activation?
What is the role of adenylyl cyclase in the activation of protein kinase A (PKA)?
What is the role of adenylyl cyclase in the activation of protein kinase A (PKA)?
Which of the following is an example of a slow molecular change in cell behavior?
Which of the following is an example of a slow molecular change in cell behavior?
Which of the following is a common target enzyme for G-proteins?
Which of the following is a common target enzyme for G-proteins?
How does the continuous activation of G-proteins affect the gut?
How does the continuous activation of G-proteins affect the gut?
How do G-protein-coupled receptors activate G-proteins?
How do G-protein-coupled receptors activate G-proteins?
What is the effect of some bacterial toxins on G-proteins?
What is the effect of some bacterial toxins on G-proteins?
How does the cyclic AMP signaling pathway activate enzymes?
How does the cyclic AMP signaling pathway activate enzymes?
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Study Notes
Nitric Oxide Signaling
- Nitric oxide (NO) crosses the plasma membrane and activates intracellular enzyme directly
- NO binds to guanylyl cyclase, forming cyclic GMP, which is an intracellular signal that activates a signaling cascade
- Cyclic GMP causes muscles to relax, allowing vessels to dilate and increasing blood flow
- Example: Viagra enhances penile erection by blocking degradation of cyclic GMP, prolonging NO signal
General Principles of Cell Signaling
- Signals can act over a long or short range
- Each cell responds to a limited set of signals
- A cell's response to a signal can be fast or slow
Intracellular Signals
- Some hormones cross the plasma membrane and bind to intracellular receptors
- Some dissolved gases, such as NO, cross the plasma membrane and activate intracellular enzymes directly
- Examples of intracellular signaling molecules: cyclic GMP, cyclic AMP, Ca2+, and proteins
- Many intracellular signaling proteins act as molecular switches, switching from an inactive to an active state when a signal is received
Molecular Switches
- GTP-binding proteins hydrolyze their bound GTP to GDP, using their own intrinsic GTPase activity
- Cyclic AMP pathway: many intracellular signals acting via G-protein-linked receptors affect the activity of adenylyl cyclase
Second Messengers
- The original signal usually doesn't enter the cell
- Examples of second messengers: cAMP, NO, IP3, and DAG
- Some G proteins activate membrane-bound enzymes, such as adenylyl cyclase and phospholipase C
The Inositol Phospholipid Pathway
- Triggers a rise in intracellular Ca2+
- Rise in intracellular Ca2+ triggers many biological processes
G-Protein-Coupled Receptors
- Stimulation of GPCRs activates G-protein subunits
- G-protein α-subunit switches itself off by hydrolyzing its bound GTP
- Implication of G-protein always being on: continuous flow of Cl- and water into the gut lumen, resulting in diarrhea and dehydration
G-Proteins and Ion Channels
- Some G proteins directly regulate ion channels, slowing heart beat
G-Protein-Coupled Receptors and Disease
- Some bacterial toxins cause disease by altering the activity of G proteins
Cyclic AMP Signaling Pathway
- Can activate enzymes and turn on genes
- PKA is activated by cyclic AMP
- Adenylyl cyclase synthesizes cAMP, while cAMP phosphodiesterase degrades cAMP
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