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1
Q

had developed mechanisms for responding to physical and chemical changes in
their environment.

A

unicellular organisms

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2
Q

Process in bacteria that respond to chemical signals that are secreted by their
neighbors and accumulate at higher population density

A

quorum sensing

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3
Q

allows bacteria to coordinate their behavior, including their motility, antibiotic production, spore formation, and sexual conjugation

A

quorum sensing

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4
Q
  • a peptide released when a haploid individual is ready to mate
  • signals cells of the opposite mating type to stop proliferating and prepare to mate
A

mating factor

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5
Q

simple intracellular signaling pathway activated by an extracellular signal molecule

A
  1. signal molecule binds to a receptor
    protein that is embedded in the plasma
    membrane of the target cell.
  2. The receptor activates one or more intracellular signaling pathways, involving a series of signaling proteins.
  3. Finally, one or more of the
    intracellular signaling proteins alters the
    activity of effector proteins and thereby the
    behavior of the cell
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6
Q

Effector proteins

A
  1. metabolic enzyme
  2. transcription regulatory protein
  3. cytoskeletal protein
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7
Q

altered metabolism

A

metabolic enzyme

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8
Q

altered gene expression

A

transcription regulatory protein

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9
Q

altered cell shape or movement

A

cytoskeletal protein

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10
Q

have evolved to allow the collaboration and coordination of different tissues and cell types.

A

intracellular signaling

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11
Q

mediate mainly communication between cells in multicellular organisms

A

extracellular signal
molecules

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12
Q

cells produce signals that they
themselves respond to

A

autocrine signaling

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13
Q

Four forms of intercellular signaling.

A
  1. CONTACT-DEPENDENT
  2. PARACRINE
  3. SYNAPTIC
  4. ENDOCRINE
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14
Q

requires cells to be in direct membrane–
membrane contact

A

CONTACT-DEPENDENT

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15
Q

depends on local mediators that are
released into the extracellular space and
act on neighboring cells.

A

Paracrine

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16
Q

performed by neurons that
transmit signals electrically along their
axons and release neurotransmitters at
synapses, which are often located far
away from the neuronal cell body.

A

SYNAPTIC

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17
Q

depends on
endocrine cells, which secrete hormones
into the bloodstream for distribution
throughout the body

A

ENDOCRINE

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18
Q

kinds of extracellular signal molecules

A

proteins, small peptides, amino acids,
nucleotides, steroids, retinoids, fatty acid
derivatives, and even dissolved gases
such as nitric oxide and carbon
monoxide

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19
Q

responds by means of a receptor

A

target cell

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20
Q
  • has a complex structure that is shaped
    to recognize the signal molecule with high specificity
A

binding site of receptors

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21
Q

In most cases, receptors are ______ ____ on the target-cell surface

A

transmembrane proteins

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22
Q

receptor protein bind an extracellular signal molecule ____ that allow them to become activated and generate various intracellular signals

A

ligand

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23
Q

each cell is programmed to respond to
specific ____ of extracellular
signals

A

combinations

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24
Q

cell responds to the signals ____

A

selectively

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25
Q

One of the key challenges in cell biology

A

determine how a cell integrates all of
this signaling information in order to
make decisions—to divide, to move, to
differentiate, and so on

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26
Q
  • a form of programmed cell death
A

cell apoptosis

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27
Q

often depends on a combination of signals that promote both cell division and survival,
as well as signals that stimulate cell growth

A

cell proliferation

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28
Q

-differentiation into a nondividing state
- frequently requires a different combination of survival and differentiation signals that must override any signal to divide.

A

terminal differentiation

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29
Q

often has different effects on different types of target cells

A

signal molecule

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30
Q

decreases the rate of action potential firing in heart pacemaker cells and stimulates the production of saliva by salivary gland cells , even though the receptors are the same on both cell types

A

acetylcholine

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31
Q

Function of acetylcholine in heart pacemaker cells

A

decreases the rate of action potential firing

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32
Q

Function of acetylcholine in salivary gland cells

A

stimulates the production of saliva

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33
Q

The different effects of acetylcholine in these cell types result from differences in the

A

intracellular signaling proteins, effector proteins, and genes that are activated

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34
Q

simply induces the cell to respond according to its predetermined state

A

extracellular signal

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35
Q

acetylcholine causes the cells to contract by binding to a different receptor protein in

A

skeletal muscle cell

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36
Q

cell-surface receptors act as signal transducers

A

signal transducers

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37
Q

How cell-surface receptors act as signal transducers

A

converting an extracellular
ligand-binding event into
intracellular signals that alter the
behavior of the target cell

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38
Q

three major classes of cellsurface receptor proteins

A
  1. ion-channel coupled receptors
  2. G-protein-coupled receptors
  3. enzyme-coupled receptors
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39
Q
  • also known as transmitter-gated ion channels or ionotropic receptors
  • involved in rapid synaptic signaling between nerve cells and other electrically excitable target cells
  • mediated by a small number of neurotransmitters
A

Ion-channel-coupled receptors

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40
Q

Ion-channel-coupled receptors a.k.a

A

transmitter-gated ion channels or ionotropic receptors

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41
Q
  • act by indirectly regulating the activity of a
    separate plasma-membrane-bound target protein, which is generally either an enzyme or an ion channel
  • trimeric GTP-binding protein (G protein)
A

G-protein-coupled receptors

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42
Q

plasma-membrane-bound target protein, which is generally either?

A

enzyme or an ion channel

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43
Q

mediates the interaction between the activated receptor and this target protein

A

trimeric GTP-binding protein (G protein)

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44
Q
  • function as enzymes or associated directly with enzymes
  • single-pass transmembrane proteins
  • ligand-binding outside the cell
  • enzyme-binding site inside
  • protein kinases
A

enzyme-coupled receptors

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45
Q

enzyme-coupled receptors function as

A

enzymes or associated directly with enzymes

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46
Q

enzyme-coupled receptors has _____-____
outside the cell

A

ligand-binding

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47
Q

enzyme-coupled receptors have _____-____
Inside the cell

A

enzyme-binding site

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48
Q
  • relay signals received by cell-surface receptors into the cell interior.
  • often called second messengers
A

intracellular signaling molecules

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49
Q

intracellular signaling molecules are often called

A

second messengers

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50
Q

Some intracellular signaling molecules are:

A

small chemicals or water-soluble
molecules or lipid-soluble

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51
Q

intracellular signaling molecules pass the signal on by ____ to and ____the
behavior of selected signaling or effector proteins.

A

binding
altering

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52
Q

When they receive a signal, they switch from an inactive to an active state, until another process switches them off, returning them to their inactive state

A

molecular switches

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53
Q

largest class of molecular switches consists of proteins that are activated or inactivated by

A

phosphorylation

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54
Q

For proteins in molecular switches, the switch is thrown in one direction by a ____ ___ and in the othrt direction by a ____ _____

A

protein kinase
protein phosphatase

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55
Q

addition of phosphate group

A

kinase

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56
Q

removes the phosphate groups

A

phosphatase

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57
Q

human genome encodes about ____ kinases and about ___phosphatases

A

520
150

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58
Q

two main types of protein kinase

A

serine/threonine kinases
tyrosine kinases

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59
Q

The other important class of molecular switches consists of ___-_____ proteins

A

GTP-binding

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60
Q

on” (actively signaling) state when ?

A

GTP is bound

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61
Q

“off” state when ?

A

GDP is bound

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62
Q

two major types
of GTP-binding proteins

A
  1. trimeric GTP-binding proteins (G proteins)
  2. monomeric GTP-binding proteins(small monometic GTPases)
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63
Q

help relay signals from G-protein-coupled receptors that activate them

A

trimeric GTP-binding proteins (G proteins)

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64
Q

help relay signals from many classes of cell-surface receptors

A

monomeric GTP-binding proteins(small monometic GTPases)

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65
Q

drive the proteins into an “off” state by
increasing the rate of hydrolysis of bound GTP.

A

GTPase-activating proteins

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66
Q

activate GTP-binding proteins by promoting the release of bound GDP, which allows a new GTP to bind.

A

guanine nucleotide
exchange factors (GEFs)

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67
Q

portrayed as a series of activation
steps

A

signaling pathway

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68
Q

very common in signaling systems

A

double-negative activation

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69
Q

an activated intracellular ____ molecule should interact only with the
appropriate ___ targets, and, likewise, the ___should only be activated by the appropriate ___signal

A

signaling
downstream
targets
upstream

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70
Q

How does a signal remain strong, precise, and specific under these noisy conditions?

A
  • defense comes from the high affinity and specificity
  • ability of downstream target proteins to simply ignore such signals
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71
Q

respond only when the upstream signal
reaches a high concentration or activity level

A

downstream target proteins

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72
Q

downstream target proteins responds only when

A

upstream signal
reaches a high concentration or activity level

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73
Q

involves scaffold proteins

A

localization

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74
Q

holds the proteins in close proximity, they can interact at high local concentrations and be sequentially activated rapidly

A

scaffold

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75
Q
  • form only transiently in response
    to an extracellular signal and rapidly disassemble when the signal is gone
  • assemble around a receptor after an extracellular signal molecule has activated
A

signaling complexes

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76
Q

bring together groups of interacting signaling proteins into signaling complexes, often before a signal has been received

A

scaffold proteins

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77
Q

scaffold proteins bring together groups of interacting signaling proteins into

A

signaling complexes

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78
Q

phosphorylated during the activation process

A

cytoplasmic tail of the activated receptor

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79
Q

phosphorylated
cytoplasmic tail of the
receptor serve as

A

docking
sites

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80
Q

modified phospholipid molecules

A

phosphoinositides

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81
Q

In yet other cases, receptor activation leads to the production of ________ which then recruit specific intracellular signaling proteins

A

phosphoinositides

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82
Q

function of an intracellular signaling system

A

to detect and measure a specific stimulus in
one location of a cell and then generate an
appropriately timed and measured response at another location

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83
Q

behaviors that produce a response
that is appropriate for the cell function that system controls

A
  1. response
  2. sensitivity
  3. dynamic range
  4. persistence
  5. signal processing
  6. integration
  7. coordination
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84
Q

timing varies dramatically in different signaling systems, according to the speed required for the response

A

Response

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85
Q

number or affinity; amplification

A

sensitivity to extracellular signals

86
Q

increasing the sensitivity
of a signaling system is signal ___

A

amplification

87
Q
  • a signaling system is related to its sensitivity
  • responsiveness
A

dynamic range

88
Q
  • A transient response of less than
    a second
    -prolonged or even permanent response is required in cell fate decisions
    during development
A

persistence

89
Q

appropriate in some synaptic responses

A

transient response of less than
a second

90
Q

required in cell fate decisions
during development

A

prolonged or even permanent response

91
Q
  • convert a simple signal into a complex response
  • a simple input signal is converted into an oscillatory response
A

signal processing

92
Q

allows a response to be governed by multiple inputs

A

integration

93
Q

multiple responses in one cell can be achieved by a single
extracellular signal

A

coordination

94
Q

where speed of response depends on

A

nature of intracellular signaling
molecules

95
Q

rapid response

A

changes in proteins

96
Q

changes in gene expression and the synthesis of new proteins

A

response usually requires many minutes or
hours, regardless of the mode of signal delivery

97
Q

the response fades when a signal ceases

A

Adult tissues

98
Q

smoothly graded response

A

hyperbolic

99
Q

Other signaling systems generate significant responses only when the signal concentration rises beyond some _____ value

100
Q

two types of abrupt responses

A
  • sigmoidal
  • discontinuous or all-or-none
101
Q

low concentrations of stimulus do not have much effect, but then the response rises steeply and continuously at intermediate stimulus levels

102
Q

response switches
on completely (and often irreversibly) when the signal reaches some threshold
concentration

A

discontinuous or all-or-none

103
Q

the output of a process acts back to regulate that same process

A

feedback loops

104
Q

output stimulates
its own production

A

positive feedback –

105
Q

output inhibits its
own production

A

negative feedback

106
Q

if of only moderate strength, its effect will
be simply to steepen the response to the signal, generating a sigmoidal response

A

Positive feedback

107
Q

If the positive feedback is of only moderate strength, its effect will be simply to ___ the response to the signal, generating a?

A

steepen
sigmoidal response

108
Q

if the feedback is strong enough in positive feedback, it can produce
an ___ response

A

all-or-none

109
Q

his response goes hand in hand with
a further property: once the responding system has switched to the high level of
activation

A

self-sustaining

110
Q

can exist in either a “switched-off” or a “switched-on” state,

111
Q
  • a transient extracellular signal can
    induce long-term changes
  • muscle-cell specification
A

Positive feedback

112
Q

all cells in a population do not
respond ____ to the same
concentration of extracellular signal

A

identically

113
Q
  • counteracts the effect of a
    stimulus and thereby
  • limits the level of the response
A

negative feedback

114
Q

A delayed negative feedback with a long enough delay can produce responses that ____

115
Q

if the stimulus is suddenly increased,
however, the system responds strongly again, but, again, the response rapidly
decays.

A

adaptations

116
Q

a prolonged exposure to a stimulus decreases the cells’
response to that level of stimulus.

A

adaptation or desensitization

117
Q

a strong response modifies the signaling machinery that resets itself to become
less responsive

A

strong response

118
Q

respond to changes in the concentration of an extracellular signal molecule

A

adaptation or desensitization

119
Q
  • form the largest family of cell-surface
  • Our senses of sight, smell, and taste depend on them.
A

G-protein-coupled receptors (GPCRs)

120
Q

Despite the chemical and functional diversity of the signal molecules that activate them, all GPCRs have a similar structure:

A

consist of a single polypeptide
chain that threads back and forth across the lipid bilayer seven times, forming a
cylindrical structure

121
Q

use G proteins to relay the signal into the cell interior.

A

Plasma membrane

122
Q

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

A

trimeric GTP-binding proteins (G
protein)

123
Q

three protein subunits of G Protein

A

α, β, and γ

124
Q

the α subunit has GDP bound and the G protein is inactive

A

unstimulated state

125
Q

When a GPCR is activated, it acts like a

A

guanine nucleotide
exchange factor (GEF)

126
Q

When a GPCR is activated, __ subunit release its bound GDP →
binding of ___ → conformational
changes → dissociation of the GTP bound Gα subunit from the Gβγ pair

127
Q
  • synthesized from ATP by an enzyme called adenylyl cyclase
  • rapidly and continuously destroyed by phosphodiesterases
A

cyclic AMP (cAMP)

128
Q

synthesis of cyclic AMP (cAMP)

A

adenylyl cyclase

129
Q

destruction of cyclic AMP (cAMP)

A

phosphodiesterases

130
Q

regulate the production of cyclic AMP

A

G proteins

131
Q

stimulatory G protein activates adenylyl cyclase

132
Q

inhibitory G protein which then inhibits adenylyl cyclase

133
Q

ADP ribosylation
that alters the Gs α subunit - inactive

A

cholera toxin

134
Q

causing the severe diarrhea that characterizes cholera

A

cholera toxin

135
Q
  • made by the bacterium that causes pertussis (whooping cough)
    -ADP
    ribosylation of the α subunit of Gi
A

pertussis toxin

136
Q

activate cyclic-AMP
dependent protein kinase (PKA)

137
Q

cAMP activate?

A

cyclic-AMP
dependent protein kinase (PKA)

138
Q

phosphorylates specific serines or
threonines, regulating their activity

A

(PKA) cyclic-AMP
dependent protein kinase

139
Q

In the inactive state, PKA consists of a

A

two catalytic subunits
and two regulatory subunits

140
Q

activated state of PKA consists of

A

released catalytic
subunits

141
Q

some responses mediated by cAMP depend on changes in the _____ of specific genes

A

transcription

142
Q

cAMP activates the gene
that encodes this hormone

A

somatostatin

143
Q

regulatory region of the somatostatin gene contains a short cis-regulatory sequence, called

A

cyclic AMP response element (CRE)

144
Q

specific transcription regulator recognizes cis-regulatory sequence

A

CRE-binding
(CREB) protein

145
Q

When PKA is activated by cAMP, it phosphorylates CREB on a single serine; phosphorylated CREB
then recruits a transcriptional coactivator called

A

CREB-binding protein (CBP)

146
Q

stimulates the transcription of the target genes

A

CREB-binding protein (CBP)

147
Q

transform a short cAMP signal into a long-term change in a cell

148
Q

activate the plasma-membrane-bound
enzyme

A
  • G-proteins
149
Q

plasma-membrane-bound enzyme

A

phospholipase C-β (PLCβ)

150
Q

acts on inositol phospholipid
signaling pathway

A

phospholipase

151
Q

activates phospholipase C-β

152
Q

The activated phospholipase two products

A

diacylglycerol & inositol
1,4,5-triphosphate (IP3)

153
Q

acts as a second messenger in some signaling pathways.

A

Cyclic AMP (cAMP)

154
Q

water-soluble molecule that leaves the plasma membrane and diffuses
rapidly through the cytosol

155
Q

IP3 when it reaches ER

A

binds to and opens IP3-gated Ca2+-release channels (also called IP3 receptors)

156
Q

Ca2+ stored in the ER is released through the open channels, quickly raising the concentration of Ca2+ in the

157
Q

activate protein
kinase C (PKC)

A

diacyglycerol

158
Q

diacyglycerol activate?

A

protein
kinase C (PKC)

159
Q

G protein that activates
GEF (guanine nucleotide
exchange factor) that activates
a monomeric GTPase (Rho
family) which regulates the actin
cytoskeleton

160
Q

G12 activates?

A

GEF (guanine nucleotide
exchange factor)

161
Q

GEF (guanine nucleotide
exchange factor) activate?

A

monomeric GTPase (Rho
family)

162
Q

monomeric GTPase (Rho
family) regulate?

A

the actin
cytoskeleton

163
Q

directly activate or inactivate ion channels in
the plasma membrane of the target cell

164
Q

released by the vagus nerve reduces the heart rate

A

acetylcholine

165
Q

smell and vision depend on
____ that regulate ion channels

166
Q
  • recognize odors
    -act through cAMP
    -When stimulated by odorant binding, they activate an olfactory-specific G protein (known as Golf)
A

olfactory receptors

167
Q

olfactory receptors act through

168
Q

olfactory receptors activates?

A

olfactory specific binding G protein
(Golf)

169
Q

olfactory specific binding G protein (Golf) activates?

A

adenylyl cyclase

170
Q

How many olfactory receptors in human

171
Q

activates its own
characteristic set of olfactory
receptor neurons

A

each odorant

172
Q

chemical signals detected in a different part of
the nose that are used in communication between members of the same species.

A

pheromones

173
Q

highly sensitive, signal-detection process

174
Q

involved in signal-detection process.

A

Cyclic-nucleotide-gated ion channels

175
Q

crucial cyclic nucleotide in signal-detection process.

A

cyclic GMP

176
Q

degraded of cAMP in vision is by

A

cyclic GMP phosphodiesterase

177
Q

-the fastest G-protein-mediated responses known in vertebrates
-receptor activation stimulated by light causes
a fall rather than a rise in the level of the cyclic nucleotide

A

visual transduction responses

178
Q

visual transduction responses receptor activation stimulated by ___ causes a ___ in the level of cyclic nucleotide

179
Q

responsible for noncolor vision in dim light

A

rod photoreceptors (rods)

180
Q

are responsible for color vision in bright light

A

cone photoreceptors (cones)

181
Q

depend on GPCRs that regulate ion channels

A

smell and vision

182
Q
  • contains a stack of discs
  • contains cyclic-GMP-gated cation channels.
A

phototransduction apparatus

183
Q

plasma membrane surrounding the outer segment of the rod contains ?

A

cyclic-GMP-gated cation channels.

184
Q

bound to cyclic-GMP-gated cation
channel to keeps them open in the dark

A

cyclic GMP

185
Q
  • causes a hyperpolarization (which inhibits synaptic signaling)
186
Q

membrane potential moves to a more negative value

A

Hyperpolarization

187
Q

Hyperpolarization results because?

A

the light-induced activation of rhodopsin molecules in the disc membrane decreases the cyclic GMP concentration and closes the cation channels in the surrounding plasma membrane

188
Q

activated by a photon of light

189
Q

alters the conformation of the G protein transducin (Gt)

A

activated rhodopsin molecule

190
Q

activate cyclic GMP phosphodiesterase

A

transducin α subunit

191
Q

transducin α subunit activates?

A

cyclic GMP phosphodiesterase

192
Q

hydrolyzes cyclic GMP

A

cyclic GMP phosphodiesterase

193
Q

cyclic GMP phosphodiesterase hydrolyzes?

A

cyclic GMP

194
Q

hydrolyzes cyclic GMP will cause ___ levels fall

195
Q

alters conformation of ____ (Gt) →
activate the cyclic GMP ___________
→ ___ cyclic GMP → ____ levels fall

A

transducin
phosphodiesterase
hydrolyzes
GMP

196
Q

rods use _____ feedback loops

197
Q

-rhodopsin-specific protein kinase
-phosphorylates the cytosolic tail of activated rhodopsin on multiple serines, partially inhibiting the ability of the rhodopsin to activate transducin

A

rhodopsin kinase (RK)

198
Q

inhibitory protein then binds to the phosphorylated rhodopsin, further inhibiting rhodopsin’s activity

199
Q

signaling molecules, that is hydrophobic, small, readily pass across the plasma membrane

A

nitric oxide (NO)

200
Q

one of the NO function

A

relax smooth muscles in the walls of blood vessels

201
Q

stimulates NO synthesis

A

acetylcholine

202
Q

diffuses out of the cell where it
is produced and into neighboring smooth muscle cells

A

nitric oxide (NO)

203
Q

depend on relay chains of intracellular signaling proteins and second messengers. T

A

intracellular signaling pathways that GPCRs trigger

204
Q

amplifying cascade of stimulatory
signals

A

relay chains

205
Q

GPCRs 3 modes of adaptation

A
  1. receptor sequestration
  2. receptor down-regulation
  3. receptor inactivation
206
Q

temporarily moved to the interior of the
cell (internalized) so that they no longer have access to their ligand

A

receptor sequestration

207
Q

they are destroyed in lysosomes after internalization

A

receptor down-regulation

208
Q

become altered so that they can no longer interact with G proteins

A

receptor inactivation

209
Q

depends on their phosphorylation by GPCR kinases

A

desensitization of the GPCRs

210
Q
  • prevents the activated receptor from interacting with G proteins
  • adaptor protein
A

arrestin desensitization

z (5 decks)

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