Signal Transduction and GPCRs

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Questions and Answers

What role does cyclic AMP (cAMP) play in the signaling pathway initiated by glucagon?

It serves as a second messenger that transmits the signal internally. (correct)

It functions exclusively outside the cell.

It acts as a first messenger to initiate the cascade.

It directly activates glucagon receptors.

Which component of the cyclic-AMP cascade directly converts ATP into cyclic AMP?

Glucagon Receptor

Glucagon

Protein Kinase A

Adenylyl cyclase (correct)

In the context of hormone signaling, what is the primary function of a second messenger like cAMP?

To directly catalyze metabolic reactions.

To bind to hormone receptors on the cell surface.

To transport hormones across the cytoplasmic membrane.

To amplify the signal initiated by the first messenger. (correct)

How does glucagon lead to an elevation of intracellular cAMP levels when blood glucose is low?

By activating the glucagon receptor, which stimulates adenylyl cyclase. Signup and view all the answers

What is the primary role of Protein Kinase A in the context of the cyclic-AMP signaling cascade?

To phosphorylate target proteins, leading to a physiological response. Signup and view all the answers

What role does cyclic AMP play in the signal transduction process mediated by GPCRs?

It serves as a secondary messenger that activates protein kinases. Signup and view all the answers

Which of the following correctly describes the phosphoinositide signaling pathway?

It initiates the hydrolysis of phosphatidylinositol, generating inositol trisphosphate and diacylglycerol. Signup and view all the answers

How does hormonal regulation influence signal transduction through GPCRs?

Hormones increase the number of GPCRs on the cell surface. Signup and view all the answers

What is a key feature of receptor amplification in GPCR signaling?

It allows for a single ligand binding to activate multiple G proteins. Signup and view all the answers

Which statement correctly describes the role of second messengers in GPCR signaling?

Second messengers facilitate the amplification of the signal within the cell. Signup and view all the answers

Which of the following is NOT a characteristic of G protein-coupled receptors?

They only interact with receptor tyrosine kinases. Signup and view all the answers

What is the primary function of G proteins in GPCR-mediated signal transduction?

To link activated receptors with downstream signaling pathways. Signup and view all the answers

In the context of the cyclic AMP signal pathway, which kinase is primarily activated as a result of increased cyclic AMP levels?

Protein kinase A Signup and view all the answers

What triggers the activation of the α subunit of a G protein in GPCR signaling?

Binding of the ligand to the receptor Signup and view all the answers

Which molecule is produced by adenylyl cyclase upon activation by the glucagon receptor?

Cyclic AMP Signup and view all the answers

In the phosphoinositide signaling pathway, which of the following is produced after the activation of phospholipase C?

Inositol trisphosphate (IP3) Signup and view all the answers

How does GPCR signaling achieve signal amplification?

By generating multiple second messengers from one activated receptor Signup and view all the answers

What is the ultimate cellular role of cyclic AMP in GPCR signaling?

Activate protein kinases Signup and view all the answers

Which of the following represents a key difference between the cyclic AMP and phosphoinositide signaling pathways?

Phosphoinositide pathway leads to generation of DAG and IP3 Signup and view all the answers

What is the function of glucagon in hormonal regulation of glucose levels?

To stimulate the breakdown of glycogen to glucose Signup and view all the answers

After activation, what happens to the α subunit of the G protein when it hydrolyzes GTP?

It re-associates with the β-γ complex Signup and view all the answers

Study Notes