12 Flashcards
1
Q
had developed mechanisms for responding to physical and chemical changes in
their environment.
A
unicellular organisms
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
3
Q
allows bacteria to coordinate their behavior, including their motility, antibiotic production, spore formation, and sexual conjugation
A
quorum sensing
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
5
Q
simple intracellular signaling pathway activated by an extracellular signal molecule
A
- signal molecule binds to a receptor
protein that is embedded in the plasma
membrane of the target cell. - The receptor activates one or more intracellular signaling pathways, involving a series of signaling proteins.
- Finally, one or more of the
intracellular signaling proteins alters the
activity of effector proteins and thereby the
behavior of the cell
6
Q
Effector proteins
A
- metabolic enzyme
- transcription regulatory protein
- cytoskeletal protein
7
Q
altered metabolism
A
metabolic enzyme
8
Q
altered gene expression
A
transcription regulatory protein
9
Q
altered cell shape or movement
A
cytoskeletal protein
10
Q
have evolved to allow the collaboration and coordination of different tissues and cell types.
A
intracellular signaling
11
Q
mediate mainly communication between cells in multicellular organisms
A
extracellular signal
molecules
12
Q
cells produce signals that they
themselves respond to
A
autocrine signaling
13
Q
Four forms of intercellular signaling.
A
- CONTACT-DEPENDENT
- PARACRINE
- SYNAPTIC
- ENDOCRINE
14
Q
requires cells to be in direct membrane–
membrane contact
A
CONTACT-DEPENDENT
15
Q
depends on local mediators that are
released into the extracellular space and
act on neighboring cells.
A
Paracrine
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
17
Q
depends on
endocrine cells, which secrete hormones
into the bloodstream for distribution
throughout the body
A
ENDOCRINE
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
19
Q
responds by means of a receptor
A
target cell
20
Q
- has a complex structure that is shaped
to recognize the signal molecule with high specificity
A
binding site of receptors
21
Q
In most cases, receptors are ______ ____ on the target-cell surface
A
transmembrane proteins
22
Q
receptor protein bind an extracellular signal molecule ____ that allow them to become activated and generate various intracellular signals
A
ligand
23
Q
each cell is programmed to respond to
specific ____ of extracellular
signals
A
combinations
24
Q
cell responds to the signals ____
A
selectively
25
One of the key challenges in cell biology
determine how a cell integrates all of
this signaling information in order to
make decisions—to divide, to move, to
differentiate, and so on
26
- a form of programmed cell death
cell apoptosis
27
often depends on a combination of signals that promote both cell division and survival,
as well as signals that stimulate cell growth
cell proliferation
28
-differentiation into a nondividing state
- frequently requires a different combination of survival and differentiation signals that must override any signal to divide.
terminal differentiation
29
often has different effects on different types of target cells
signal molecule
30
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
acetylcholine
31
Function of acetylcholine in heart pacemaker cells
decreases the rate of action potential firing
32
Function of acetylcholine in salivary gland cells
stimulates the production of saliva
33
The different effects of acetylcholine in these cell types result from differences in the
intracellular signaling proteins, effector proteins, and genes that are activated
34
simply induces the cell to respond according to its predetermined state
extracellular signal
35
acetylcholine causes the cells to contract by binding to a different receptor protein in
skeletal muscle cell
36
cell-surface receptors act as signal transducers
signal transducers
37
How cell-surface receptors act as signal transducers
converting an extracellular
ligand-binding event into
intracellular signals that alter the
behavior of the target cell
38
three major classes of cellsurface receptor proteins
1. ion-channel coupled receptors
2. G-protein-coupled receptors
3. enzyme-coupled receptors
39
- 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
Ion-channel-coupled receptors
40
Ion-channel-coupled receptors a.k.a
transmitter-gated ion channels or ionotropic receptors
41
- 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)
G-protein-coupled receptors
42
plasma-membrane-bound target protein, which is generally either?
enzyme or an ion channel
43
mediates the interaction between the activated receptor and this target protein
trimeric GTP-binding protein (G protein)
44
* function as enzymes or associated directly with enzymes
* single-pass transmembrane proteins
* ligand-binding outside the cell
* enzyme-binding site inside
* protein kinases
enzyme-coupled receptors
45
enzyme-coupled receptors function as
enzymes or associated directly with enzymes
46
enzyme-coupled receptors has _____-____
outside the cell
ligand-binding
47
enzyme-coupled receptors have _____-____
Inside the cell
enzyme-binding site
48
- relay signals received by cell-surface receptors into the cell interior.
- often called second messengers
intracellular signaling molecules
49
intracellular signaling molecules are often called
second messengers
50
Some intracellular signaling molecules are:
small chemicals or water-soluble
molecules or lipid-soluble
51
intracellular signaling molecules pass the signal on by ____ to and ____the
behavior of selected signaling or effector proteins.
binding
altering
52
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
molecular switches
53
largest class of molecular switches consists of proteins that are activated or inactivated by
phosphorylation
54
For proteins in molecular switches, the switch is thrown in one direction by a ____ ___ and in the othrt direction by a ____ _____
protein kinase
protein phosphatase
55
addition of phosphate group
kinase
56
removes the phosphate groups
phosphatase
57
human genome encodes about ____ kinases and about ___phosphatases
520
150
58
two main types of protein kinase
serine/threonine kinases
tyrosine kinases
59
The other important class of molecular switches consists of ___-_____ proteins
GTP-binding
60
on” (actively signaling) state when ?
GTP is bound
61
“off” state when ?
GDP is bound
62
two major types
of GTP-binding proteins
1. trimeric GTP-binding proteins (G proteins)
2. monomeric GTP-binding proteins(small monometic GTPases)
63
help relay signals from G-protein-coupled receptors that activate them
trimeric GTP-binding proteins (G proteins)
64
help relay signals from many classes of cell-surface receptors
monomeric GTP-binding proteins(small monometic GTPases)
65
drive the proteins into an “off” state by
increasing the rate of hydrolysis of bound GTP.
GTPase-activating proteins
66
activate GTP-binding proteins by promoting the release of bound GDP, which allows a new GTP to bind.
guanine nucleotide
exchange factors (GEFs)
67
portrayed as a series of activation
steps
signaling pathway
68
very common in signaling systems
double-negative activation
69
an activated intracellular ____ molecule should interact only with the
appropriate ___ targets, and, likewise, the ___should only be activated by the appropriate ___signal
signaling
downstream
targets
upstream
70
How does a signal remain strong, precise, and specific under these noisy conditions?
- defense comes from the high affinity and specificity
- ability of downstream target proteins to simply ignore such signals
71
respond only when the upstream signal
reaches a high concentration or activity level
downstream target proteins
72
downstream target proteins responds only when
upstream signal
reaches a high concentration or activity level
73
involves scaffold proteins
localization
74
holds the proteins in close proximity, they can interact at high local concentrations and be sequentially activated rapidly
scaffold
75
- 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
signaling complexes
76
bring together groups of interacting signaling proteins into signaling complexes, often before a signal has been received
scaffold proteins
77
scaffold proteins bring together groups of interacting signaling proteins into
signaling complexes
78
phosphorylated during the activation process
cytoplasmic tail of the activated receptor
79
phosphorylated
cytoplasmic tail of the
receptor serve as
docking
sites
80
modified phospholipid molecules
phosphoinositides
81
In yet other cases, receptor activation leads to the production of ________ which then recruit specific intracellular signaling proteins
phosphoinositides
82
function of an intracellular signaling system
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
83
behaviors that produce a response
that is appropriate for the cell function that system controls
1. response
2. sensitivity
3. dynamic range
4. persistence
5. signal processing
6. integration
7. coordination
84
timing varies dramatically in different signaling systems, according to the speed required for the response
Response
85
number or affinity; amplification
sensitivity to extracellular signals
86
increasing the sensitivity
of a signaling system is signal ___
amplification
87
- a signaling system is related to its sensitivity
- responsiveness
dynamic range
88
- A transient response of less than
a second
-prolonged or even permanent response is required in cell fate decisions
during development
persistence
89
appropriate in some synaptic responses
transient response of less than
a second
90
required in cell fate decisions
during development
prolonged or even permanent response
91
- convert a simple signal into a complex response
- a simple input signal is converted into an oscillatory response
signal processing
92
allows a response to be governed by multiple inputs
integration
93
multiple responses in one cell can be achieved by a single
extracellular signal
coordination
94
where speed of response depends on
nature of intracellular signaling
molecules
95
rapid response
changes in proteins
96
changes in gene expression and the synthesis of new proteins
response usually requires many minutes or
hours, regardless of the mode of signal delivery
97
the response fades when a signal ceases
Adult tissues
98
smoothly graded response
hyperbolic
99
Other signaling systems generate significant responses only when the signal concentration rises beyond some _____ value
threshold
100
two types of abrupt responses
* sigmoidal
* discontinuous or all-or-none
101
101
low concentrations of stimulus do not have much effect, but then the response rises steeply and continuously at intermediate stimulus levels
sigmoidal
102
response switches
on completely (and often irreversibly) when the signal reaches some threshold
concentration
discontinuous or all-or-none
103
the output of a process acts back to regulate that same process
feedback loops
104
output stimulates
its own production
positive feedback –
105
output inhibits its
own production
negative feedback
106
if of only moderate strength, its effect will
be simply to steepen the response to the signal, generating a sigmoidal response
Positive feedback
107
If the positive feedback is of only moderate strength, its effect will be simply to ___ the response to the signal, generating a?
steepen
sigmoidal response
108
if the feedback is strong enough in positive feedback, it can produce
an ___ response
all-or-none
109
his response goes hand in hand with
a further property: once the responding system has switched to the high level of
activation
self-sustaining
110
can exist in either a “switched-off” or a “switched-on” state,
bistable
111
* a transient extracellular signal can
induce long-term changes
* muscle-cell specification
Positive feedback
112
all cells in a population do not
respond ____ to the same
concentration of extracellular signal
identically
113
- counteracts the effect of a
stimulus and thereby
- limits the level of the response
negative feedback
114
A delayed negative feedback with a long enough delay can produce responses that ____
oscillate
115
if the stimulus is suddenly increased,
however, the system responds strongly again, but, again, the response rapidly
decays.
adaptations
116
a prolonged exposure to a stimulus decreases the cells’
response to that level of stimulus.
adaptation or desensitization
117
a strong response modifies the signaling machinery that resets itself to become
less responsive
strong response
118
respond to changes in the concentration of an extracellular signal molecule
adaptation or desensitization
119
- form the largest family of cell-surface
- Our senses of sight, smell, and taste depend on them.
G-protein-coupled receptors (GPCRs)
120
Despite the chemical and functional diversity of the signal molecules that activate them, all GPCRs have a similar structure:
consist of a single polypeptide
chain that threads back and forth across the lipid bilayer seven times, forming a
cylindrical structure
121
use G proteins to relay the signal into the cell interior.
Plasma membrane
122
When an extracellular signal molecule binds to a GPCR, the receptor undergoes
a conformational change that enables it to activate a
trimeric GTP-binding proteins (G
protein)
123
three protein subunits of G Protein
α, β, and γ
124
the α subunit has GDP bound and the G protein is inactive
unstimulated state
125
When a GPCR is activated, it acts like a
guanine nucleotide
exchange factor (GEF)
126
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
α
GTP
127
- synthesized from ATP by an enzyme called adenylyl cyclase
- rapidly and continuously destroyed by phosphodiesterases
cyclic AMP (cAMP)
128
synthesis of cyclic AMP (cAMP)
adenylyl cyclase
129
destruction of cyclic AMP (cAMP)
phosphodiesterases
130
regulate the production of cyclic AMP
G proteins
131
stimulatory G protein activates adenylyl cyclase
Gs
132
inhibitory G protein which then inhibits adenylyl cyclase
Gi
133
ADP ribosylation
that alters the Gs α subunit - inactive
cholera toxin
134
causing the severe diarrhea that characterizes cholera
cholera toxin
135
- made by the bacterium that causes pertussis (whooping cough)
-ADP
ribosylation of the α subunit of Gi
pertussis toxin
136
activate cyclic-AMP
dependent protein kinase (PKA)
cAMP
137
cAMP activate?
cyclic-AMP
dependent protein kinase (PKA)
138
phosphorylates specific serines or
threonines, regulating their activity
(PKA) cyclic-AMP
dependent protein kinase
139
In the inactive state, PKA consists of a
two catalytic subunits
and two regulatory subunits
140
activated state of PKA consists of
released catalytic
subunits
141
some responses mediated by cAMP depend on changes in the _____ of specific genes
transcription
142
cAMP activates the gene
that encodes this hormone
somatostatin
143
regulatory region of the somatostatin gene contains a short cis-regulatory sequence, called
cyclic AMP response element (CRE)
144
specific transcription regulator recognizes cis-regulatory sequence
CRE-binding
(CREB) protein
145
When PKA is activated by cAMP, it phosphorylates CREB on a single serine; phosphorylated CREB
then recruits a transcriptional coactivator called
CREB-binding protein (CBP)
146
stimulates the transcription of the target genes
CREB-binding protein (CBP)
147
transform a short cAMP signal into a long-term change in a cell
CREB
148
activate the plasma-membrane-bound
enzyme
* G-proteins
149
plasma-membrane-bound enzyme
phospholipase C-β (PLCβ)
150
acts on inositol phospholipid
signaling pathway
phospholipase
151
activates phospholipase C-β
Gq
152
The activated phospholipase two products
diacylglycerol & inositol
1,4,5-triphosphate (IP3)
153
acts as a second messenger in some signaling pathways.
Cyclic AMP (cAMP)
154
water-soluble molecule that leaves the plasma membrane and diffuses
rapidly through the cytosol
IP3
155
IP3 when it reaches ER
binds to and opens IP3-gated Ca2+-release channels (also called IP3 receptors)
156
Ca2+ stored in the ER is released through the open channels, quickly raising the concentration of Ca2+ in the
Cytosol
157
activate protein
kinase C (PKC)
diacyglycerol
158
diacyglycerol activate?
protein
kinase C (PKC)
159
G protein that activates
GEF (guanine nucleotide
exchange factor) that activates
a monomeric GTPase (Rho
family) which regulates the actin
cytoskeleton
G12
160
G12 activates?
GEF (guanine nucleotide
exchange factor)
161
GEF (guanine nucleotide
exchange factor) activate?
monomeric GTPase (Rho
family)
162
monomeric GTPase (Rho
family) regulate?
the actin
cytoskeleton
163
directly activate or inactivate ion channels in
the plasma membrane of the target cell
G protein
164
released by the vagus nerve reduces the heart rate
acetylcholine
165
smell and vision depend on
____ that regulate ion channels
GPCRs
166
- recognize odors
-act through cAMP
-When stimulated by odorant binding, they activate an olfactory-specific G protein (known as Golf)
olfactory receptors
167
olfactory receptors act through
cAMP
168
olfactory receptors activates?
olfactory specific binding G protein
(Golf)
169
olfactory specific binding G protein (Golf) activates?
adenylyl cyclase
170
How many olfactory receptors in human
350
171
activates its own
characteristic set of olfactory
receptor neurons
each odorant
172
chemical signals detected in a different part of
the nose that are used in communication between members of the same species.
pheromones
173
highly sensitive, signal-detection process
vision
174
involved in signal-detection process.
Cyclic-nucleotide-gated ion channels
175
crucial cyclic nucleotide in signal-detection process.
cyclic GMP
176
degraded of cAMP in vision is by
cyclic GMP phosphodiesterase
177
-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
visual transduction responses
178
visual transduction responses receptor activation stimulated by ___ causes a ___ in the level of cyclic nucleotide
light
fall
179
responsible for noncolor vision in dim light
rod photoreceptors (rods)
180
are responsible for color vision in bright light
cone photoreceptors (cones)
181
depend on GPCRs that regulate ion channels
smell and vision
182
- contains a stack of discs
- contains cyclic-GMP-gated cation channels.
phototransduction apparatus
183
plasma membrane surrounding the outer segment of the rod contains ?
cyclic-GMP-gated cation channels.
184
bound to cyclic-GMP-gated cation
channel to keeps them open in the dark
cyclic GMP
185
- causes a hyperpolarization (which inhibits synaptic signaling)
light
186
membrane potential moves to a more negative value
Hyperpolarization
187
Hyperpolarization results because?
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
activated by a photon of light
rhodopsin
189
alters the conformation of the G protein transducin (Gt)
activated rhodopsin molecule
190
activate cyclic GMP phosphodiesterase
transducin α subunit
191
transducin α subunit activates?
cyclic GMP phosphodiesterase
192
hydrolyzes cyclic GMP
cyclic GMP phosphodiesterase
193
cyclic GMP phosphodiesterase hydrolyzes?
cyclic GMP
194
hydrolyzes cyclic GMP will cause ___ levels fall
GMP
195
alters conformation of ____ (Gt) →
activate the cyclic GMP ___________
→ ___ cyclic GMP → ____ levels fall
transducin
phosphodiesterase
hydrolyzes
GMP
196
rods use _____ feedback loops
negative
197
-rhodopsin-specific protein kinase
-phosphorylates the cytosolic tail of activated rhodopsin on multiple serines, partially inhibiting the ability of the rhodopsin to activate transducin
rhodopsin kinase (RK)
198
inhibitory protein then binds to the phosphorylated rhodopsin, further inhibiting rhodopsin’s activity
arrestin
199
signaling molecules, that is hydrophobic, small, readily pass across the plasma membrane
nitric oxide (NO)
200
one of the NO function
relax smooth muscles in the walls of blood vessels
201
stimulates NO synthesis
acetylcholine
202
diffuses out of the cell where it
is produced and into neighboring smooth muscle cells
nitric oxide (NO)
203
depend on relay chains of intracellular signaling proteins and second messengers. T
intracellular signaling pathways that GPCRs trigger
204
amplifying cascade of stimulatory
signals
relay chains
205
GPCRs 3 modes of adaptation
1. receptor sequestration
2. receptor down-regulation
3. receptor inactivation
206
temporarily moved to the interior of the
cell (internalized) so that they no longer have access to their ligand
receptor sequestration
207
they are destroyed in lysosomes after internalization
receptor down-regulation
208
become altered so that they can no longer interact with G proteins
receptor inactivation
209
depends on their phosphorylation by GPCR kinases
desensitization of the GPCRs
210
* prevents the activated receptor from interacting with G proteins
* adaptor protein
arrestin desensitization
211
