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Physiology > Intracellular Signaling at the Cell Membrane > Flashcards

Intracellular Signaling at the Cell Membrane Flashcards

1
Q

Receptors in the cell membrane are key in what 2 functions?

A

Detecting extracellular signals and modifying cell function based on those signals

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2
Q

What are the intracellular events that transform the extracellular signal into an intracellular signal?

A

Transduction

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3
Q

What do these events all involve?
-Source of some 2nd messengers
-Site where some 2nd messengers accumulate
-Site where ionic 2nd messengers are regulated
- Important site where regulatory proteins and enzymes localize and integrate signaling

A

The cell membrane

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4
Q

Describe the initial activation intracellular signaling model.

A

Ligand Binding: A signaling molecule (ligand) attaches to a cell membrane receptor.

Receptor Activation: This binding activates the receptor.

Intracellular Protein Activation: The activated receptor triggers an intracellular protein.

Second Messenger Production: This protein generates a second messenger.

Second Messenger Activation: The second messenger activates another protein.

Signaling Cascade: This protein sets off a series of reactions.

Cellular Effects: The cascade leads to cellular responses or changes.

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5
Q

What is an effector?

A

A cellular component that carries out specific actions in response to a signal.

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6
Q

What’s another name for the first messanger?

A

Lignan

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7
Q

Describe the deactivation of the intracellular signaling model.

A

Decreased First Messenger: When the concentration of the first messenger decreases,
Inactive Receptor: The cell membrane receptor is no longer activated.
Inactive Protein: The protein associated with the receptor becomes inactive.
Second Messenger Depletion: The protein or enzyme stops producing the second messenger.
Second Messenger Inactivation: Another mechanism reduces or inactivates the second messenger.
Ineffective Activation: With the low second messenger concentration, it can’t activate its target protein.
Inactive Effectors: Effectors are no longer activated.

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8
Q

What’s another term for deactivation?

A

Downregulation

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9
Q

Why does downregulation take place?

A

To prevent overstimulation or maintain a balance in cellular signaling.

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10
Q

What is the extracellular signal known as?

A

First messenger

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11
Q

What happens during receptor activation?

A

An increased cytosolic or membrane concentrations of a 2nd messenger

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12
Q

What is the process by which a relatively small initial signal or stimulus is greatly increased in magnitude or effect as it progresses through a signaling pathway

A

Amplification

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13
Q

What are 3 reasons for signal termination?

A

Inactivation of receptor (i.e. no 1st messenger) or receptor-associated effectors
degradation or removal of 2nd messenger
negative feedback

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14
Q

What are 3 types of cell membrane receptors?

A

1.) Ion channel-coupled receptors
2.) G-protein-coupled receptors
3.) Enzyme-coupled receptors

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15
Q

Which is the largest family of cell membrane receptors?

A

G-protein-coupled receptors (800)

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16
Q

Almost half of medications act on what receptors/pathways?

A

G-protein-coupled

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17
Q

What is a G-protein?

A

Guanine nucleotide

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18
Q

True or False. The activated G-protein will modify the activity of an enzyme.

A

True.

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19
Q

Does the activation G-protein have intrinsic GTP-ase activity? Or does it get its energy elsewhere?

A

Intrinsic

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20
Q

When GTP hydrolyzed
into GDP, what happens?

A

Then the G-protein is inactive

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21
Q

What are the 3 G-protein subunits?

A

alpha, betta, gamma

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22
Q

How are the g- protein subunits bound: Unstimulated?

A

α is bound to GDP, and βγ is bound to α

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23
Q

How are the g- protein subunits bound: Stimulated?

A

α subunit releases GDP, replacing it with GTP and the α subunit disengages from the βγ subunits

24
Q

What happens when α unit hydrolyzes GTP into GDP?

A

It becomes inactivated again

25
Q

Gs binds to and activates _______________.
This membrane-bound enzyme that converts ATP to _________.

A

adenylyl cyclase, cAMP

26
Q

(Gs) cAMP binds to which enzyme?

A

Protein kinase A (PKA)

27
Q

What does PKA phosphorylate?

A

A multitude of effector proteins

28
Q

CREB is an important target protein that ________ phosphorylates.

A

PKA

29
Q

Adenylyl cyclase catalyzes the conversion of what? To what?

A

The conversion of ATP to cAMP

30
Q

What enzyme catalyzes the inactivation of cAMP? The turning off process?

A

Cyclic AMP phosphodiesterase

31
Q

True or False.
Sometimes βγ subunits activate effectors on their own, without “using” a 2nd messenger

A

True. During Gi and Gq

32
Q

Which GPCR uses Ca+2 and IP3 and DAG as 2nd messenger systems

A

Gq

33
Q

Which 2nd messenger that has one effect? It causes release of Ca+2 from where it’s stored in the endoplasmic reticulum (ER).

A

IP3

34
Q

Which Gq second messenger system has many effects, it can bind to and activate a number of proteins and modulation of a very large range of effectors

A

Ca2+

35
Q

(Gq)What second messenger system does Ca2+ bind to?

A

Calmodulin

36
Q

(Gq)How much more increase in Ca2+ concentrations is there in a cell that is “activated” rather than inactive?

A

100X increase. Can reach Ca+2 concentrations of 10 micromolar or more.

37
Q

(Gq)What happens when the concentration of Ca+2 increases in the cytosol?

A

It will bind to calcium-binding proteins in the cytosol and an effect will take place.

38
Q

Each calmodulin binds to how many Ca+2 ions before it becomes activated?

A

4

39
Q

True or False. Once calmodulin is activated, it can bind to effectors.

A

True

40
Q

After a ligand binds to a receptor associated with a Gq G-protein, Gq-alpha activates ____________.

A

phospholipase C

41
Q

What does phospholipase C do?

A

It cleaves a membrane lipid into IP3 and diacylglycerol (DAG)

42
Q

What is the membrane lipid in the Gq GPCR?

A

PIP2

43
Q

(Gq) Once cleaved, _______ is water soluble – it enters the cytosol

A

IP3

44
Q

(Gq) Once cleaved, ________ is lipid soluble – it stays within the cell membrane and diffuses throughout it

A

DAG

45
Q

(Gq)IP3 activates a ________release channel in the ER

A

Ca+2

46
Q

(Gq) Both Ca+2 and DAG work together to activate membrane-bound protein __________

A

kinase C (PK C)

47
Q

What in the inhibitory G-protein that downregulates the activity of Gs?

A

Gi

48
Q

What does Gi alpha inactivates?

A

adenylyl cyclases

49
Q

What does Gi-βγ open?

A

K+ channels

50
Q

What does opening of K+ channels do?

A

Brings the cell closer to its Nernst potential for K+

51
Q

What is the Nernst potential for K+

A

-90 mV

52
Q

By having a very negative membrane potential, what tends to happen?

A

It tends to cause most cells to be “less” activated.

53
Q

Calcium concentrations inside the cell are almost ________ times (lower/higher) than outside the cell at rest

A

10,000/lower

54
Q

In ion channels, if the channel allows sodium to enter, the membrane becomes more “inside (positive/negative)”?

What is this known as?

A

Positive/depolarization

55
Q

If the channel allows more potassium to leave, the membrane becomes more “inside positive/negative”?

What is this known as?

A

Negative/hyperpolarization

Physiology (11 decks)

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