Cyclic AMP Pathway and Cell Behavior Changes Quiz

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Questions and Answers

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?

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?

GTP-binding proteins (correct)

Protein kinase A

Cyclic AMP

Calcium ions

What effect does an increase in cyclic GMP have on muscles?

Promotes muscle relaxation Signup and view all the answers

Which enzyme is responsible for hydrolyzing bound GTP to GDP in GTP-binding proteins?

GTPase activity Signup and view all the answers

Which of the following molecules is NOT typically associated with the cyclic AMP signaling pathway?

Diacylglycerol (DAG) Signup and view all the answers

Which enzyme is a common target for G-protein activation in the cyclic AMP pathway?

Adenylyl cyclase Signup and view all the answers

How do some dissolved gases like Nitric Oxide activate intracellular enzymes?

By binding directly and activating the enzyme Signup and view all the answers

Which second messenger is involved in triggering a rise in intracellular Ca2+?

Inositol 1,4,5-triphosphate (IP3) Signup and view all the answers

Which intracellular event can be triggered by a rise in intracellular cyclic AMP?

Activation of gene transcription Signup and view all the answers

Which of the following is NOT a common target enzyme for G-protein activation?

Protein kinase C Signup and view all the answers

What is the role of adenylyl cyclase in the activation of protein kinase A (PKA)?

Adenylyl cyclase synthesizes cAMP, which then activates PKA Signup and view all the answers

Which of the following is an example of a slow molecular change in cell behavior?

Activation of gene transcription Signup and view all the answers

Which of the following is a common target enzyme for G-proteins?

Adenylyl cyclase Signup and view all the answers

How does the continuous activation of G-proteins affect the gut?

It causes diarrhea and dehydration Signup and view all the answers

How do G-protein-coupled receptors activate G-proteins?

By causing the G-protein to exchange its bound GDP for GTP Signup and view all the answers

What is the effect of some bacterial toxins on G-proteins?

They activate G-proteins Signup and view all the answers

How does the cyclic AMP signaling pathway activate enzymes?

By activating PKA, which then activates enzymes Signup and view all the answers

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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Description

Test your knowledge on the Cyclic AMP pathway and how intracellular signals can affect gene transcription and cell behavior. Explore the molecular changes that can lead to quick alterations in cell behavior.