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Questions and Answers
What is the primary function of a signal transduction pathway?
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?
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?
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?
What is a common role of second messengers in signal transduction pathways?
Which of the following best describes paracrine signaling?
Which of the following best describes paracrine signaling?
During the fight or flight response, which type of signaling is most likely involved?
During the fight or flight response, which type of signaling is most likely involved?
Gap junctions are associated with which type of cell signaling?
Gap junctions are associated with which type of cell signaling?
Which of the following statements about G-protein coupled receptors is true?
Which of the following statements about G-protein coupled receptors is true?
What role do RGS proteins play in G-protein signaling?
What role do RGS proteins play in G-protein signaling?
Which of the following proteins is involved in the desensitization of β-adrenergic receptors?
Which of the following proteins is involved in the desensitization of β-adrenergic receptors?
What does PLC cleave to produce IP3?
What does PLC cleave to produce IP3?
How can different G-proteins affect signal transduction pathways?
How can different G-proteins affect signal transduction pathways?
What acts as a secondary messenger activated by calcium-sensing proteins?
What acts as a secondary messenger activated by calcium-sensing proteins?
In the fight or flight response, which substance primarily signals the need for energy?
In the fight or flight response, which substance primarily signals the need for energy?
Which secondary messenger is produced alongside IP3 during the cleavage of PIP2?
Which secondary messenger is produced alongside IP3 during the cleavage of PIP2?
Which of the following can be considered a ligand-gated ion channel's function in GPCR signaling?
Which of the following can be considered a ligand-gated ion channel's function in GPCR signaling?
What role do G-protein coupled receptors play in signal transduction?
What role do G-protein coupled receptors play in signal transduction?
Which molecule is involved in the fight or flight response by increasing heart rate?
Which molecule is involved in the fight or flight response by increasing heart rate?
Which second messenger is primarily involved in the activation of protein kinase A (PKA)?
Which second messenger is primarily involved in the activation of protein kinase A (PKA)?
How does glucagon affect cellular processes during the fight or flight response?
How does glucagon affect cellular processes during the fight or flight response?
What is one effect of adrenaline binding to its GPCR in muscle cells?
What is one effect of adrenaline binding to its GPCR in muscle cells?
What happens when adenosine binds to its receptors in relation to GPCRs?
What happens when adenosine binds to its receptors in relation to GPCRs?
What does crosstalk between GPCRs and receptor tyrosine kinases indicate?
What does crosstalk between GPCRs and receptor tyrosine kinases indicate?
Which of the following statements is true regarding different G-proteins and transduction pathways?
Which of the following statements is true regarding different G-proteins and transduction pathways?
Which substance inhibits the action of adenylyl cyclase via GPCRs?
Which substance inhibits the action of adenylyl cyclase via GPCRs?
What is the primary effect of adrenaline on glycogen in the liver during stress?
What is the primary effect of adrenaline on glycogen in the liver during stress?
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.
