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Phys Exam two > G-Protein Linked Receptors > Flashcards

G-Protein Linked Receptors Flashcards

1
Q

G-protein linked receptors have how many transmembrane proteins?

A

seven-pass

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2
Q

What do g-protein-linked receptors contain?

A

extracellular domain w/ ligand binding site and an intracellular domain w/binding site for a heterotrimeric G-protein.

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3
Q

What do heterotrimeric G-proteins do?

A

Couple the receptor to their cytosolic targets, which are commonly ion channels or enzymes

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4
Q

What do heterotrimeric G-proteins consist of and what do they do?

A

alpha-subunit - mediate signaling in most signaling pathways.
Beta gamma subunits - mediate signaling in some signaling pathways.

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5
Q

What initiates g-protein subunit dissociation?

A

GTP/GDP exchange

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6
Q

When is the G-protein switched off?

A

When the GDP is bound to the alpha subunit

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7
Q

Activation of the G-protein causes what?

A

exchange of GTP for GDP

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8
Q

What happens when GTP is bound?

A

the G-protein is switched on, alpha and beta-gamma subunits dissociate

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9
Q

How does the G-protein switch off?
What happens when GDP is bound to alpha subunit?
What happens when it is switched off?

A

By hydrolyzing GTP to GDP. GDP remains bound to alpha subunit. Alpha subunit possesses GTPase activity, which does the hydrolyzing of GTP to GDP.
Re-associates with the beta-gamma subunit

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10
Q

What does If do?

A

funny current or pacemaker current drives the potential toward threshold

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11
Q

Ica,L, what does it do?

A

L-type Ca2+ current activates at threshold and generates action potential

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12
Q

What increases cardiac beat frequency?

A

Norepinephrine released from sympathetic fibers .

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13
Q

Stimulation of If and Ica,L does what?

A

increases rate of pacemaker cell depolarization

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14
Q

What does norepinephrine do?

A

activates the B1-adrenergic receptor

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15
Q

What does the activated receptor do?

A

interacts with and activates Gs, a stimulatory G-protein.

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16
Q

What is GDP replaced by?

A

GTP

17
Q

What does Gs dissociate into?

A

alpha and beta/gamma subunit.

18
Q

GTP-bound alpha subunit stimulates what?

A

stimulates adenylyl cyclase to catalyze the generation of the second messenger cAMP from ATP

19
Q

What does cAMP bind and enhance?

To account for what?

A

camp binds to and enhances the rate of HCN channel activation to account for the change in kinetics of the funny current and increase the rate of depolarization.

20
Q

What does camp bind to that activates the catalytic subunit?

A

cAMP binds to the regulatory subunit of protein kinase A and the catalytic subunit becomes active.

21
Q

What does PKA phosphorylate and what happens after this?

A

PKA phosphorylates Cav1 channels, which changes their activity and accounts for change in Ica, L which contributes ot the rate of depolarization.

22
Q

How is greater activity involved in increasing heart rate?

A

Greater activity enhances the rate of the membrane depolarization to increase the heart rate.

23
Q

Gs/cAMP Pathway- what dissociate from the receptor?

A

the ligand and norepinephrine.

24
Q

Gs/cAMP Pathway- What part of the g-protein inactivates itself and how?

A

the alpha-subunit of the g-protein inactivates itself by hydrolyzing GTP to GDP

25
Q

Gs/cAMP Pathway- what dissociates from proteins? What do phosphodiesterase do and what do phosphates do?

A

cAMP dissociates from proteins.
Phosphodiesterases break down cAMP to AMP.
Phosphatases dephosphorylate proteins

26
Q

Gs/cAMP Pathway-

What can be activated by other receptors?

A

Gs/cAMP pathway in other cells can be activated by other receptors and can cause effects that alter (increase or decrease) the function of other proteins.

27
Q

What decreases cardiac beat frequency?

A

Acetylcholine released from parasympathetic nerve fibers decreases cardiac beat frequency.

28
Q

What decreases the pacemaker depolarization rate?

A

Inhibition of If and Ica, L

Phys Exam two (13 decks)

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