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Cell Bio > Chapter 16 > Flashcards

Chapter 16 Flashcards

1
Q

Signaling molecules are

A

Diverse

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2
Q

What kind of hormone diffuse through the plasma membrane and bind to
intracellular receptors located in the cytoplasm

A

Steroid

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3
Q

cannot pass through the plasma membrane and instead bind to cell surface receptors

A

Amino acids, peptides, and proteins

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4
Q

can produce different effects in different cells by
using different receptors and intracellular pathways

A

Acetylcholine

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5
Q

Cortex matters in…

A

Cell signaling

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6
Q

Fast signal response occur with changes in the…

A

Activity of an Intracellular profein

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7
Q

Slow signal responses occur in changes in…

A

Transcription/translation (need time for protein synthesis)

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8
Q

The location of a receptor depends on the

A

Nature of signal

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9
Q

Hydrophilic signals bind to

A

Cell surface receptors

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10
Q

Hydrophobic signals cross the __ and bind ___ receptors

A

Hydrophobic, Intracellular

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11
Q

Hydrophobic hormones are derivatives of

A

Cholesterol or tyrosine

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12
Q

With steroid hormone signaling the receptor may be in the

A

Cytoplasm or nucleus

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13
Q

If cytoplasmic, hormone
binding stimulates
movement to

A

Nucleus

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14
Q

Steroid hormone signaling regulates…

A

Transcription of target genes

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15
Q

a stress hormone secreted by the adrenal gland
that stimulates metabolism in many target tissues & also
suppresses the immune system

A

Cortisol

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16
Q

sex hormone secreted by the ovary that induces and maintains secondary female sexual characteristics

A

Estrogen

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17
Q

sex hormone secreted by the testis that induces and maintains secondary male sexual characteristics

A

Testosterone

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18
Q

The androgen receptor (AR) binds

A

Testosterone

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19
Q

The AR gene is located on the __ chromosome

A

X

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20
Q

Dissolved gases also cross the plasma membrane directly via

A

Diffusion

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21
Q

made in endothelial cells
diffuses into smooth
muscle cells

A

Nitric oxide (NO)

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22
Q

Induces smooth muscle relaxation

A

NO

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23
Q

Nerve releases

A

Acetylcholine

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24
Q

binds to a receptor on
the surface of an endothelial cell and stimulates synthesis
and release of NO

A

Acetylcholine

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25
Q

NO diffuses into a neighboring

A

Smooth muscle cell

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26
Q

Once NO diffuses into neighboring smooth muscle cells where it

A

Binds guanylyl cyclase and induces smooth muscle relaxation

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27
Q

Guanylyl cyclase converts

A

GTP to cGMP

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28
Q

relaxes smooth muscle

A

cGMP

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29
Q

Role of cGMP phosphodiesterase

A

degrades cGMP to end the signal

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30
Q

blocks cGMP phosphodiesterase, prolongs relaxation of smooth muscle, promotes dilation of blood vessels

A

Viagra

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31
Q

Hydrophilic signals bind

A

cell-surface receptors

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32
Q

How many classes of receptors

A

3

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33
Q

What are the classes of cell surface receptors

A
  1. Ion channel coupled receptor
  2. G protein coupled receptors
  3. Enzyme coupled receptor
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34
Q

Ion channel or ligand gated coupled receptors convert a

A

Chemical signal into electrical

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35
Q

have seven transmembrane alpha-helices

A

GPCRs

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36
Q

activates a membrane-bound G-protein

A

Ligand binding

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37
Q

Activated G-protein __ a target protein

A

activates (or inhibits)

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38
Q

Large and widespread receptor family (>700 in humans)

A

G-protein-coupled receptors (GPCRs)

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39
Q

Prominent in multi-cellular organisms

A

Enzyme-coupled receptors

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40
Q

Drugs can mimic signaling molecules __ block their action

A

or

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41
Q

Intracellular signaling pathways convert a

A

Extracellular signal to Intracellular

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42
Q

Roles of Intracellular signaling pathways…

A

Relay, amplify, integrate, distribute

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43
Q

sometimes using a scaffold protein to hold multiple components close together

A

Intracellular signaling pathways

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44
Q

Modulate response by regulating the activity of upstream components
(feedback)

A

Intracellular signaling pathways

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45
Q

can adjust the response to an extracellular signal

A

Feedbac k regulation

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46
Q

can produce sophisticated responses to signals

A

Feedback regulation

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47
Q

How to turn signals on and off?

A
  1. Protein phosphorylation and dephosphorylation
  2. GDP/GTP exchange and GTP hydrolysis
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48
Q

Protein phosphorylation and dephosphorylation requires what two proteins and what modification

A

two proteins, a kinase and phosphatase and covalent modification of the target protein

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49
Q

Involves non-covalent binding

A

GDP/GTP exchange and GTP hydrolysis

50
Q

The GTPase activity of the GTP-binding protein functions as a

A

Timer

51
Q

relay messages from G-protein-coupled receptors

A

Trimeric GTP-binding proteins (a.k.a. G-proteins)

52
Q

help other cell-surface receptors relay signals

A

Monomeric GTPases

53
Q

Protein kinases transfer a phosphate from ATP onto
a protein. T or F

A

True

54
Q

A GTP-binding protein exchanges its bound GDP for
GTP to become activated.
True or false

A

True

55
Q

Phosphatases remove the phosphate from GTP on
GTP-binding proteins, turning them off. True or false

A

False

56
Q

Example of contact-dependent
signaling

A

Delta-Notch signaling

57
Q

seen in several developmental
signaling pathways

A

Regulated proteolysis

58
Q

Participates in cell specialization and differentiation

A

Delta noTch signaling

59
Q

Nerve cell expresses

A

Delta

60
Q

-stimulates cleavage of receptor
-fragment goes to nucleus
-Stimulates transcription

A

Delta-Notch signaling

61
Q

To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol.
True or false

A

False

62
Q

cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response.
True or false

A

False

63
Q

Extracellular signal molecules that are hydrophilic must bind to a cell- surface receptor so as to signal a target cell to change its behavior.
True or False

A

True

64
Q

Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family.
True or False

A

False

65
Q

Active acetylcholine receptors on salivary gland cells and heart muscle cells activate the same intracellular signaling pathway. True or False

A

False

66
Q

Four modes of signaling:

A

Endocrine, paracrine, neuronal, contact dependent

67
Q

Acetylcholine bonds heart muscle cells, slowing down heart rate

True or false

A

True

68
Q

When an extracellular signal molecule binds to a GPCR, the
GPCR undergoes a conformational change that enables it to bind
and activate a

A

heterotrimeric G protein

69
Q

Some G proteins activate membrane-bound enzymes such as

A

Adenylyl cyclase (generates cAMP)
Phospholipase C (generates IP3 and diacylglycerol)

70
Q

the cAMP mediates what kind of responses

A

fast and slow responses

71
Q

The phospholipase C pathway triggers a rise in

A

cytosolic Ca2+

72
Q

__ signal triggers many biological processes

A

Ca2+

73
Q

GPCRs consist of __ polypeptide chain that crosses the
membrane as __ a-helices

A

single, 7

74
Q

Heterotrimeric G proteins (a.k.a. large G proteins) contain __ subunits

A

3

75
Q

Alpha and gamma subunits are __ bound to membrane lipids

A

covalently

76
Q

Alpha subunit with bound GDP is
Alpha subunit with bound GTP is

A

inactive
active

77
Q

GTP hydrolysis by the a
subunit __
of the G protein

A

terminates activation

78
Q

alpha subunit with GTP activates (or
inhibits) a target protein for

A

as long as they remain in contact

79
Q

Many activated G proteins target

A

membrane-bound enzymes

80
Q

Activated alpha subunit stimulates

A

adenylyl cyclase

81
Q

Adenyl cyclase converts

A

ATP to cAMP, an important 2nd messenger

82
Q

adenyl cyclase is an example of a ___; multiple cAMP
molecules are produced by a single adenylyl cyclase

A

signal amplification

83
Q

cAMP phosphodiesterase converts

A

cAMP to AMP to terminate the signal

84
Q

What inhibits cAMP
phosphodiesterase, prolongs cAMP
signaling in the nervous system

A

Caffeine

85
Q

Epinephrine binds to a class of GPCRs called

A

adrenergic receptors

86
Q

Some act via cAMP
– Increase heart rate
– Promote fat breakdown in fat cells, glycogen breakdown in skeletal
muscle

A

Epinenphrine=adrenaline

87
Q

True or False
(1) A constitutively active mutant form
of PKA increases the amount of
phosphorylated phosphorylase
kinase

(2) A constitutively active mutant form
of PKA decreases the affinity of
epinephrine for the GPCR

(3) A constitutively active mutant form
of PKA increases the amount of
cAMP produced by adenylyl
cyclase

A

true
false
false

88
Q

active PKA enters the nucleus, where it…

A

phosphorylates specific transcription factors

89
Q

This is one way to convert a brief
signal into a long-term response

A

PKA/cAMP

90
Q

cleaves an inositol phospholipid to generate watersoluble IP3 and membrane-bound diacylglycerol

A

Phospholipase C

91
Q

What opens Ca2+ channels in ER membrane and increases cytoplasmic Ca2+

A

IP3

92
Q

What recruits & activate PKC (protein kinase C)

A

Diacylglycerol & Ca2+

93
Q

phosphorylates many target proteins

A

protein kinase A

94
Q

Most widespread and common calcium binding proteins in the cytosol

A

calmodulin (CaM)

95
Q

CaM (calmoduln) activates how many targets

A

several

96
Q

Calmodulin activates how many binding sites on the alpha helix

A

2

97
Q

One major target that calmodulin binds and activates to is

A

CaM-kinase

98
Q

Role of CaM-kinase

A

phosphorylates target proteins

99
Q

How do you terminate a Ca2+ signal

A

Use the Ca2+ ATPase pump to lower
the cytosolic concentration of Ca2+

100
Q

Enzyme-coupled receptors either act as

A

enzymes or form complexes with other proteins that act as enzymes

101
Q

Receptor tyrosine kinases contain an

A

intracellular tyrosine kinase domain

102
Q

recruit a complex of intracellular signaling proteins

A

Activated RTKs

103
Q

Most RTKs activate the…

A

Ras

104
Q

Some RTKs activate PI 3-Kinase to produce…

A

lipid docking sites for the activation of other enzymes

105
Q

Binding of a signal molecule induces

A

receptor dimerization

106
Q

What stimulates kinase activity & trans-autophosphorylation (each receptor phosphorylates the other) of tyrosines

A

receptor dimerization

107
Q

Each phosphorylated tyrosine recruits a

A

specific adaptor protein

108
Q

Specific adapter proteins recruited by phosphorylated tyrosines couple…

A

RTKs to other signaling molecules

109
Q

a monomeric GTPase that is anchored to the membrane

A

Ras

110
Q

Active RTK recruits proteins (including Ras-GEF) that stimulate __
Ras to exchange its __ for __

A

inactive, GDP for GTP

111
Q

Ras-GTP activates many __ targets

A

downstream

112
Q

How to terminate Ras activation

A

GTP hydrolysis is stimulated by Ras-GAP

113
Q

RTK and Ras signals are __-lived, but activation of the __ converts short signals into longer signals

A

short, MAP kinase pathway

114
Q

What kinase can act on cytoskeleton, metabolism, gene expression, etc

A

MAP Kinase

115
Q

Activating Ras mutations are found in

A

cancer

116
Q

In activating Ras mutations, when can you turn off the signal

A

Cannot turn off signaling, even in the absence of signal

117
Q

phosphorylates inositol phospholipids

A

PI 3-kinase

118
Q

After PI 3-kinase phosphorylates inositol phospholipids, following phosphorylation these lipids recruit __ signaling molecules, including….

A

intracellular, Protein Kinase 1 and Akt kinase (PKB)

119
Q

Activated Akt kinase promotes

A

cell survival and growth

120
Q

A growth factor stimulates the proliferation of cultured cells. The receptor that binds this growth factor is a receptor tyrosine kinase (RTK), and many tumor cell lines have mutations in the gene that encodes this receptor. Would the following mutations be expected to promote or inhibit uncontrolled cell proliferation?

(a) A mutation that destroys the kinase activity of the receptor

(b) A mutation that enables the receptor to dimerize in the absence of a signal
molecule

(c) A mutation that inactivates the protein tyrosine phosphatase that normally
removes the phosphates from tyrosines on the activated receptor

(d) A mutation that prevents the binding of the growth factor to the receptor

A

A. Inhibit
B. promote
C. Promote
D. Inhibit

121
Q

Where does cross talk occur between GPCR and RTK pathways?

A

phospholiase C activation, Ca2+ signaling, phosphorylation of downstream targets

122
Q

Protein Kinase A (PKA) doesn’t effect anything __

A

upstream before activated

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