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BMS 100 > Intracellular Signalling at the Cell Membrane > Flashcards

Intracellular Signalling at the Cell Membrane Flashcards

1
Q

the intracellular events that transform the extracellular signal into an intracellular signal

A

transduction

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2
Q

examples of effectors

A

protein kinases or transcription factors

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3
Q

An extracellular signal activates a ________

A

membrane-bound receptor

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4
Q

receptor activation leads to an _______ cytosolic or membrane concentration of 2nd messenger

A

increased

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5
Q

Single activated receptor → many molecules of 2nd messenger =

A

amplification

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6
Q

signal termination is due to a number of processes (3)

A
  1. inactivation of receptor (no 1st messenger) or receptor-associated effectors
  2. degradation or removal of 2nd messenger
  3. negative feedback
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7
Q

name 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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8
Q

the largest family of cell membrane receptors are

A

G-protein-coupled receptors (GPCRs)

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9
Q

800 unique G-protein-coupled receptors (GPCRs). Almost half of ________ act on these receptors or their pathways

A

medications

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10
Q

GPCR: Receptor activation → activation of a protein that binds to a _____ nucleotide

A

guanine

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11
Q

The activated G-protein is on a “timer”. Has intrinsic GTP-ase activity. When GTP hydrolyzed → GDP then the G-protein is
______

A

inactive

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12
Q

Receptor = integral transmembrane protein. Spans the membrane _ times

A

7

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13
Q

3 protein subunits:

A

α, β, γ

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14
Q

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

A

unstimulated

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15
Q

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

A

Stimulated

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16
Q

When the α unit hydrolyzes
GTP → GDP, it becomes
______ again

A

inactivated

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17
Q
  1. Ligand binds to receptor associated with a ___ G-protein
  2. G_ releases GDP and binds GTP at the alpha subunit - by detaches from G-protein
  3. G_ binds to and activates adenylyl cyclase
    - membrane-bound enzyme that converts ATP to cAMP
  4. cAMP binds to protein kinase (PK A)
    - binds to inhibitors of PK A, which then detach, and allow the activate parts of PK A to work
  5. PK A phosphorylates a multitude of effector proteins
A

Gs GPCR

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18
Q

what enzyme converts ATP to cAMP

A

adenylyl cyclase

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19
Q

what enzyme causes an inactivation of cAMP by converting it to 5’-AMP

A

cyclic AMP phosphodiesterase
- called the “turning off” process

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20
Q

Stimulates adenylyl cyclase → cAMP production. cAMP activates PK A → phosphorylation of effectors

A

Gs

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21
Q

biological impact of: Glycogenolysis,
thyroid hormone
synthesis

A

Gs

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22
Q

alpha subunit Inhibits adenylyl
cyclase → decreased cAMP production. Decreases PK A activation.

A

Gi

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23
Q

what pathway inhibits Gs pathways

A

Gi alpha

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24
Q

beta-gamma Activates K+ channels*. Creates More negative cell membrane potential.

A

Gi

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25
Q

Biological impact of reduction of
heart rate

A

Gi beta-gamma

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26
Q

Activates phospholipase C → IP3 and DAG production. IP3 → calcium release
from ER. DAG → activation of
BK C

A

Gq (a)

27
Q

Activates cGMP phosphodiesterase → decreased cGMP. Decreased cGMP → closes Na+ channels → more negative cell membrane potential.

A

Gt (a)

28
Q

biological impact: Detection of light
– rod photoreceptors in retina

A

Gt (a)

29
Q

IP3 is a 2nd messenger that has one effect →

A

it causes release of Ca+2 from where it’s stored in the endoplasmic reticulum (ER)

30
Q

Ca+2 has many effects – it can bind to and activate a number of proteins

A

modulation of a very large range
of effectors

31
Q

Good example of a Ca+2–binding protein:

A

calmodulin

32
Q

A “resting” cell (no calcium signal) has ___ micromolar of Ca+2 in the cytosol, and ____ mmol of calcium in the endoplasmic reticulum and in the extracellular space

A

0.1 micromolar and 1-3 mmol

33
Q

The concentration gradient for calcium for is very high → it ____ to enter the cytosol

A

“wants”

34
Q

A cell that is “activated” can reach Ca+2 concentrations of __ micromolar or more

A

10 mm

35
Q

When the concentration of Ca+2 ___ in the cytosol, then it will bind to calcium-binding proteins in the cytosol → an effect

A

increases

36
Q

Each calmodulin binds to ____ Ca+2 ions before it becomes activated

A

four

37
Q

IP3 is water soluble – it enters the

A

cytosol

38
Q

DAG is lipid soluble – it stays within the ________ and diffuses throughout it

A

cell membrane

39
Q

This is a ubiquitous inhibitory G-protein that
downregulates the activity of Gs

A

Gi

40
Q

Opening of K+ channels brings the cell closer to its Nernst potential for K+. What is the nernst potential of K+

A

-90mV

41
Q

what does a very negative membrane potential cause?

A

it tends to cause most cells to be “less” activated

42
Q

What would be the impact on the membrane potential if sodium enters the cell?

A

Makes the membrane potential more positive

43
Q

If the channel allows sodium to enter → the membrane becomes more “inside-positive. This is known as ___________

A

depolarization

44
Q

If the channel allows more potassium to leave → the membrane becomes more “inside-negative”. This is known as __________

A

hyperpolarization

45
Q

T or F: Making the membrane more inside-positive or more inside-negative impacts the activation of certain membrane-associated proteins

A

True

46
Q

Making the membrane more inside-positive or more inside negative impacts the activation of certain membrane-associated proteins

A

intrinsic kinase activity

47
Q

The binding of ligand ________ the receptor and
activates a tyrosine kinase within the receptor

A

dimerizes

48
Q

Ligand examples of RTKsgand examples

A

▪ Insulin
▪ Growth factors
▪ Cytokines

49
Q

what is a pathway that does not produce 2nd messengers?

A

RAS-RAF-MAP

50
Q

which system is our KEY insulin signalling system

A

PI-3-Kinase (PI3K) > Akt System

51
Q

nitric oxide synthase (NOs) on L-arginine

A

creates Nitric Oxide
- a small molecule that rapidly degrades as it is a free radical

52
Q

what causes the activation of nitric oxide synthase (NOs)

A

an increase of cytosolic calcium

53
Q

Na in the cell is

A

low

54
Q

potassium in the cell is

A

high

55
Q

calcium in the cell is

A

low

56
Q

Transmembrane proteins with ligand-binding
domain on the outer surface of the plasma membrane are called:

A

enzyme-coupled receptors

57
Q

Binding of ligand ______ the receptor and
activates a tyrosine kinase within the receptor

A

dimerizes

58
Q

ligand examples of RTK

A
  • insulin
  • growth factors
  • cytokines
59
Q

what is Ras-Raf-MAP kinase key for:

A

growth factors

60
Q

_____ is a key mediator that relaxes smooth
muscle in a wide variety of blood vessels and visceral organs

A

Nitric oxide

61
Q

Very small, hydrophobic gas that _____ and quickly through cell membranes

A

diffuses easily

62
Q

▪ It’s a second messenger – one of the only ones that can diffuse across the cell membrane and impact other cells

A

Nitric Oxide

63
Q
A

BMS 100 (37 decks)

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