G-Protein Coupled Receptors and Hormones

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Questions and Answers

What is the primary function of a signal transduction pathway?

To produce energy for the cell

To convert a signal into a cellular response (correct)

To directly communicate with adjacent cells

To block signals from traveling to their targets

Which type of signaling is characterized by hormones being secreted into the bloodstream?

Direct contact signaling

Paracrine signaling

Endocrine signaling (correct)

Synaptic signaling

In synaptic signaling, which component is primarily responsible for transmitting signals between nerve cells?

Neurotransmitters (correct)

Endocrine glands

Cytokines

Hormones

What is a common role of second messengers in signal transduction pathways?

To amplify the cellular response to a signal Signup and view all the answers

Which of the following best describes paracrine signaling?

Involves signals acting on nearby cells within a local area Signup and view all the answers

During the fight or flight response, which type of signaling is most likely involved?

Endocrine signaling Signup and view all the answers

Gap junctions are associated with which type of cell signaling?

Direct contact signaling Signup and view all the answers

Which of the following statements about G-protein coupled receptors is true?

They can activate several intracellular pathways simultaneously Signup and view all the answers

What role do RGS proteins play in G-protein signaling?

They stimulate intrinsic GTPase activity. Signup and view all the answers

Which of the following proteins is involved in the desensitization of β-adrenergic receptors?

β-adrenergic protein kinase (βARK) Signup and view all the answers

What does PLC cleave to produce IP3?

Phosphatidylinositol 4,5-bisphosphate (PIP2) Signup and view all the answers

How can different G-proteins affect signal transduction pathways?

Different G-proteins can activate the same transduction pathways. Signup and view all the answers

What acts as a secondary messenger activated by calcium-sensing proteins?

Calcium ions (Ca2+) Signup and view all the answers

In the fight or flight response, which substance primarily signals the need for energy?

Adrenaline Signup and view all the answers

Which secondary messenger is produced alongside IP3 during the cleavage of PIP2?

DAG Signup and view all the answers

Which of the following can be considered a ligand-gated ion channel's function in GPCR signaling?

To release Ca2+ and activate downstream signaling Signup and view all the answers

What role do G-protein coupled receptors play in signal transduction?

They activate specific G-proteins to facilitate signal transduction. Signup and view all the answers

Which molecule is involved in the fight or flight response by increasing heart rate?

Adrenaline Signup and view all the answers

Which second messenger is primarily involved in the activation of protein kinase A (PKA)?

cAMP Signup and view all the answers

How does glucagon affect cellular processes during the fight or flight response?

Activates glycogen breakdown Signup and view all the answers

What is one effect of adrenaline binding to its GPCR in muscle cells?

Increased contraction strength Signup and view all the answers

What happens when adenosine binds to its receptors in relation to GPCRs?

It inhibits adenylyl cyclase. Signup and view all the answers

What does crosstalk between GPCRs and receptor tyrosine kinases indicate?

Integration of multiple signals occurs. Signup and view all the answers

Which of the following statements is true regarding different G-proteins and transduction pathways?

Different G-proteins can activate the same pathway. Signup and view all the answers

Which substance inhibits the action of adenylyl cyclase via GPCRs?

Prostaglandin E1 Signup and view all the answers

What is the primary effect of adrenaline on glycogen in the liver during stress?

Stimulates glycogen breakdown. Signup and view all the answers

Study Notes

G-protein coupled receptors (GPCR)

One signal molecule can elicit different G-protein coupled receptors (GPCRs)
Different G-proteins can activate the same transduction pathways
One signal molecule can have different effects
Different G-proteins can have opposite effects on the same transduction pathways

Fight or Flight Response

When adrenaline binds to its GPCR, a G-protein activates the second messenger
Glucagon has the same effect as adrenaline
Glucagon binds to its GPCR and activates adenylyl cyclase
Adrenaline binding increases heart rate
Adrenaline binding mobilizes glucose production

Breakdown of Triacylglycerols to Fatty Acids and Glycerol (Lipolysis)

Adrenaline, glucagon, and adrenocorticotropic hormone (ACTH) stimulate lipolysis
The three hormones bind to different GPCRs
All three activate adenylyl cyclase via G αs

Inhibition of Triacylglycerols to Fatty Acids and Glycerol (Lipolysis)

Prostaglandin E1 (PGE 1) and adenosine inhibit lipolysis
The two molecules inhibit adenylyl cyclase via G αi

Insulin Signalling

Crosstalk between a tyrosine kinase receptor and a GPCR occurs in insulin signaling
Insulin signaling provides an example of integration of signals

Model of Cell Signaling

Six steps of cell-cell communication
G protein's GTPase activity determines how quickly GTP is hydrolyzed to GDP
Regulators of G-protein signaling (RGS proteins) stimulate GTPase activity
Desensitization of β-adrenergic receptors is mediated by two proteins
β-adrenergic protein kinase (βARK)
β-arrestin (βarr; also known as arrestin 2)

Secondary Messengers

cAMP, cGMP, inositol-1,4,5-triphosphate (IP3), and calcium can all act as secondary messengers
GTP-bound Gα subunit activates phospholipase C (PLC)
PLC cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) to generate inositol trisphosphate (IP3)
IP3 activates a ligand-gated ion channel
Ligand-gated ion channels release Ca2+
Ca2+ acts as a secondary messenger by activating calcium-sensing proteins
Calcium-sensing proteins include protein kinase C (PKC) and calmodulin
PLC cleavage produces diacylglycerol (DAG)
DAG activates protein kinase C (PKC)

Signal Transduction Pathway

Signal transduction pathway converts the signal into a cellular response
Signal transduction pathways can be different even if the second messengers are same

Several modes of cell communication

Direct contact
Paracrine signaling
Endocrine signaling
Synaptic signaling

Direct Contact

Gap junctions provide direct contact between cells

Paracrine Signaling

Secretory cell releases signals into the extracellular space
Signals reach target cells via the extracellular space

Endocrine Signaling

Endocrine glands secrete hormone into the blood
Blood vessels carry hormones to distant target cells

Synaptic Signaling

Nerve cells release neurotransmitters into synaptic gaps
Neurotransmitters reach target cells via diffusion
Synaptic gaps are spaces between nerve cells and target cells

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Description

Explore the functions and effects of G-protein coupled receptors (GPCRs) in response to different hormones such as adrenaline and glucagon. This quiz covers signal transduction pathways and the role of GPCRs in physiological responses like lipolysis and the fight or flight response. Test your knowledge on how these receptors can produce varied physiological outcomes.