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BIOL 3321 - cell and molecular bio > cell signaling > Flashcards

cell signaling Flashcards

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1
Q

where can cells receive signals from

A

from the environment and other cells

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2
Q

how do unicellular organisms communicate

A

through the release of signaling molecules into the environment

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3
Q

how do multicellular organisms communicate

A

through extracellular signaling molecules that function within the organism

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4
Q

list 4 examples of extracellular signaling molecules used in multicellular organisms

A

proteins, amino acids, steroids, dissolved gases

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5
Q

what are two types of receptors that a cell may have

A

cell-surface or intracellular receptor

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6
Q

what is endocrine signaling

A

signaling molecule is released into the bloodstream and acts at a distance from where it is made

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7
Q

in endocrine signaling, does the signal molecule act close to or far away from the site where it’s made

A

far away

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8
Q

in endocrine signaling, where is the signal molecule released

A

into the bloodstream

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9
Q

what is paracrine signaling

A

signaling molecule affects a cell that is in close proximity

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10
Q

what does the signal molecule affect in paracrine signaling

A

another cell that’s close by

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11
Q

does paracrine signaling occur close by or far away

A

close by

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12
Q

what is synaptic signaling

A

occurs in neurons

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13
Q

what is autocrine siganling

A

cell releases a molecule that it responds to

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14
Q

what is an example of a signal molecule released in autocrine signaling

A

growth factors

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15
Q

what is contact-dependent signaling

A

signal remains bound to the surface of the cell and contact to the target cell is required

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16
Q

in extracellular signaling, describe what happens in the cell once the signal molecule/ligand binds to the receptor

A

it activates one or more signaling pathways, and this will alter the activity of an effector protein, and the effector protein will cause changes in the cell

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17
Q

what two things might an intracellular siganling molecule be

A

a chemical or a protein

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18
Q

how do protein signaling molecules behave

A

like molecular switches

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19
Q

what are chemical signaling molecules called

A

second messengers

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20
Q

list some examples of second messengers

A

Ca2+ ions, cGMP, cAMP, DAG, IP3

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21
Q

are second messengers proteins?

A

no, they’re nonprotein

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22
Q

how heavy are second messengers

A

low molecular weight

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23
Q

list two advantages of second messengers

A

they can diffuse through the cytosol faster than proteins, and they facilitate amplification of the extracellular signal

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24
Q

explain how proteins may act as molecular switches

A

they can switch into an active or inactive form as a result of their phosphorylation state

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25
Q

what two things mediate phosphorylation

A

kinases and phosphatases

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26
Q

what do kinases do

A

phosphorylate specific amino acid residues

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27
Q

what do phosphatases do

A

remove specific phosphate groups

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28
Q

name the two types of protein kinases that animal cells contain

A

protein tyrosine kinase (PTK) and Ser/Thr kinases

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29
Q

other than phosphorylation state, binding of ____ controls the active and inactive forms of proteins

A

GTP/GDP

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30
Q

T or F: a signal molecule can have different effects on different target cells

A

true

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31
Q

state the two forms of cellular responses

A

fast and slow responses

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32
Q

what is a fast cellular response

A

changes in the activity or function of proteins that already exist in the cell

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33
Q

what is a slow cellular response

A

changes in the amounts of specific proteins produced by a cell through changes in gene expression

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34
Q

how many domains do cell surface receptors have

A

3

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35
Q

name the 3 domains of cell surface receptors

A

extracellular, transmembrane, and intracellular domain

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36
Q

T or F: each receptor generally only binds a single signaling molecule or a group of structurally related molecules

A

true

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37
Q

name the 3 main classes of cell surface receptors that mediate signal transduction

A

ion-channel-coupled receptors
G protein-coupled receptors
enzyme-coupled receptors

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38
Q

what is the most numerous type of receptor

A

GPCRs

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39
Q

list some different ligands that GPCRs respond to

A

photons, odorants, tastants, hormones, NTs, and chemoattractants

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40
Q

what percentage of all prescription drugs target the GPCR superfamily

A

30%

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41
Q

what does salmeterol do

A

acts as an agonist for epinephrine; it binds to GPCRs on smooth muscle cells of the airway to facilitate respiration

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42
Q

what does the GPCR activate

A

a G protein

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43
Q

list the basic structure of a GPCR

A

7 transmembrane alpha helical regions
4 extracellular segments
4 cytosolic segments

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44
Q

how many extracellular and cytosolic segments does a GPCR have

A

4 each

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45
Q

what type of helices do GPCRs have

A

alpha helices

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46
Q

describe how the helices of GPCRs are situated at the membrane

A

they span the membrane; transmembrane helices

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47
Q

how many transmembrane alpha helices do GPCRs have

A

7

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48
Q

why are G proteins called G proteins

A

because they bind GDP or GTP

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49
Q

name the two classes of G proteins used in signaling

A

heterotrimeric and monomeric

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50
Q

which type of G protein, heterotrimeric or monomeric, associates with GPCRs

A

heterotrimeric

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51
Q

T or F: heterotrimeric G proteins act as molecular switches

A

true

52
Q

what controls the activation state of G proteins

A

GDP vs GTP bound to it

53
Q

what is the G protein bound to in the inactive state

A

GDP

54
Q

in regards to G protein activation, what converts the GDP to GTP

A

GEFs

55
Q

what is a GEF

A

guanine nucleotide exchange factor

56
Q

what is the G protein bound to in its active state

A

GTP

57
Q

once the G protein is in its active state, what happens to the signal

A

the signal will leave and bind to activate other proteins

58
Q

in regards to G protein inactivation, what converts the GTP to GDP

A

GAP

59
Q

what is GAP

A

GTPase activation protein

60
Q

in the conversion of GTP to GDP, where does the GTPase come from

A

its intrinsic GTPase of the G protein

61
Q

T or F: in the active conformation, the G protein can bind to other proteins

A

true

62
Q

T or F: in the inactive conformation, the G protein can bind to other proteins

A

false; it can only bind to other proteins while in the active state

63
Q

list the 3 subunits of the heterotrimeric G protein

A

alpha, beta, gamma

64
Q

which subunit of heterotrimeric G protein contains the GTPase

A

alpha

65
Q

which subunits of the heterotrimeric G protein are always bound together

A

b and Y

66
Q

which subunits of the heterotrimeric G protein are bound to the PM via covalently linked lipids

A

a and y

67
Q

how are the a and y subunits of the heterotrimeric G protein bound to the PM

A

through covalently linked lipids

68
Q

which subunit of the heterotrimeric G protein gives it its specificity in terms of what it activates

A

the a subunit

69
Q

how many families of G protein are there based on the a subunit

A

4

70
Q

which family of G proteins activates adenylyl cyclase

A

Gs

71
Q

how does a GPCR become active

A

a signal molecule will bind to it

72
Q

once the GPCR is active, what can it do

A

bind the G protein

73
Q

list one target of G proteins

A

adenylyl cyclase

74
Q

where is adenylyl cyclase located

A

on the PM

75
Q

describe how G proteins can activate/inactivate ion channels in the form of regulating blood glucose

A

glucagon binds to GPCR present on liver cells, liver breaks down glycogen into glucose = blood glucose levels raise, homeostasis will eventually be reached, then when blood glucose levels decrease the alpha cells of the pancreas will release glucagon and this will repeat

76
Q

is the regulation of blood glucose levels a fast or slow protein response

A

fast protein response

77
Q

how is adenylyl cyclase stimulated

A

stimulated by the active Ga subunit of the G protein

78
Q

what does adenylyl cyclase produce

A

cAMP (a second messenger)

79
Q

how does adenylyl cyclase produce cAMP

A

ATP –> cAMP

80
Q

how many catalytic domains does adenylyl cyclase have

A

2

81
Q

which side of the PM contains the 2 catalytic subunits of adenylyl cylase

A

cytosolic side

82
Q

what does cAMP activate

A

protein kinase A (PKA)

83
Q

why can’t the conversion of ATP to cAMP in adenylyl cyclase go on forever?

A

the binding of the G protein to adenylyl cyclase enhances the intrinsic GTPase activity of the Ga subunit resulting in its inactivation

84
Q

what amino acids does PKA add a phosphate to

A

serine or threonine

85
Q

how many subunits does PKA have

A

2

86
Q

name the 2 PKA subunits

A

catalytic and regulatory

87
Q

describe the mechanism of PKA activation

A

cAMP binds to the regulatory subunit = conf change = catalytic sites dissociate = PKA is active and can phosphorylate residues

88
Q

describe the orientation of the PKA subunits when PKA is inactive

A

regulatory and catalytic subunits are intact

89
Q

describe the orientation of the PKA subunits when PKA is active

A

catalytic subunits have dissociated

90
Q

where is PKA located

A

in the liver

91
Q

what two enzymes does PKA target in the liver

A

glycogen synthase
glycogen phosphorylase kinase (GPK)

92
Q

what does glycogen synthase do

A

converts glucose to glycogen

93
Q

what happens when PKA phosphorylates glycogen synthase

A

it inhibits its catalytic activity, so glucose is not converted to glycogen

94
Q

what happens when PKA phosphorylates glycogen phosphorylase kinase

A

it activates it = it can phosphorylate glycogen phosphorylase

95
Q

what does glycogen phosphorylase kinase add a P to

A

glycogen phosphorylase

96
Q

what does glycogen phosphorylase do

A

stimulates the breakdown of glycogen

97
Q

what is produced when glycogen phosphorylase breaks down glycogen

A

glucose 1-phosphate

98
Q

what happens to glucose 1-phosphate in the liver

A

it’s converted to glucose 6-phosphate, and then to glucose by phosphatase

99
Q

what enzyme converts G6P to glucose in the liver

A

phosphatase

100
Q

how is glucose transported across the PM of liver cells into the bloodstream

A

by the transmembrane carrier GLUT2

101
Q

what is GLUT2

A

a transmembrane carrier that brings glucose into the blood from liver cells

102
Q

how many G proteins can 1 activated receptor activate

A

100

103
Q

how many adenylyl cyclase molecules can each G protein activate

A

1

104
Q

how many cAMPs can each AC make

A

100

105
Q

how many PKAs does each cAMP activate

A

1

106
Q

how many targets can each PKA activate

A

10

107
Q

how many targets can glycogen phosphorylase kinase activate

A

10

108
Q

how many G1P molecules does each glycogen phosphorylase create from glycogen

A

100

109
Q

how many glucose molecules are made from one signal

A

10^8 glucose molecules

110
Q

list some targets of PKA other than enzymes

A

ion channels, chromosomal proteins (ie Histone H1), and transcription factors (ie CREB)

111
Q

what is CREB

A

a transcription factor

112
Q

what is the name of CREB

A

CRE-binding protein

113
Q

what is the name for CRE

A

cAMP response element

114
Q

what is the cAMP-response element

A

a cis-reg sequence

115
Q

what does CREB do

A

controls genes that contain a cis-reg sequence (CRE)

116
Q

what genes have the CRE as part of their gene-control region?

A

genes involved for the enzymes of gluconeogenesis

117
Q

when might we need increased production of the genes that code for the GNG enezymes

A

in conditions of prolonged fasting

118
Q

is production of the GNG genes in conditions of prolonged fasting a slow or fast response

A

SLOW

119
Q

describe how the GNG proteins get produced, starting at PKA activation

A

the catalytic subunits of PKA translocate to the nucleus, and then PKA phosphorlyates CREB at Ser 113. P-CREB binds as a dimer onto CRE, and it also binds a coactivator (CBP/300). This results in transcription of the target genes

120
Q

at which site does PKA phosphorylate CREB

A

Ser 113

121
Q

in what form does CREB bind to CRE

A

as a dimer

122
Q

what co-activator binds to CREB when it’s bound to CRE

A

CBP/300

123
Q

what is receptor inactivation

A

a mechanism of desensitization frequently used by GPCRs

124
Q

in receptor inactivation, how does the GPCR become inactivated

A

via phosphorylation

125
Q

describe how desensitization occurs in GPCRs

A

the activated GPCR activates a GPCR kinase (GRK) located in the cell, and this phosphorylates multiple sites on the GPCR. this allows the protein Arrestin to come in and bind to the receptor

126
Q

in desensitization, what protein comes in to bind to the GPCR once the GPCR has been phosphorylated by a GRK

A

Arrestin

127
Q

what are 2 outcomes of a GPCR once it’s desensitized

A

it can be recycled back to the cell surface or be degraded in lysosomes

BIOL 3321 - cell and molecular bio (19 decks)

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