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AAA BIO107: Cell and Molecular Biology > 5. Cell Signaling > Flashcards

5. Cell Signaling Flashcards

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1
Q

principles of cell signalling

A

mechanisms for responding to
physical and chemical changes in
their environment

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2
Q

3 principles of cell signaling

A
  1. exchange of mating factors
  2. mating
  3. new a cell
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3
Q

4 protein process of cell signaling

A
  1. extracellular signal molecule
  2. receptor protein
  3. intracellular signaling proteins
  4. effector proteins
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4
Q

3 effector proteins

A
  1. metabolic enzyme
  2. transcription regulatory protein
  3. cytoskeletal protein
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5
Q

Effector protein that altered cell shape or movement

A

cytoskeletal protein

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6
Q

Effector protein that altered gene expression

A

transcription regulatory protein

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7
Q

Effector protein that altered metabolism

A

metabolic enzyme

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8
Q

cells produce signals that they
themselves respond to

A

autocrine signalling

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9
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 signalling

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10
Q

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

A

endocrine signalling

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11
Q

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

A

paracrine signalling

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12
Q

2 mechanisms of receptors

A

cell-surface receptors
intracellular receptors

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13
Q

communication between cells in multicellular organisms is mediated by

A

extracellular signal molecules

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14
Q

extracellular signal molecule

A

ligand

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15
Q

Reception of the signals depends on ___ at the cell surface, which bind the signal molecule

A

receptor proteins

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16
Q

they process the signal inside the
receiving cell and distributing it to the appropriate intracellular targets

A

intracellular signaling proteins

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17
Q

the targets that lie at the end of signalling pathways are generally. altered in some way by the incoming signal and implement the appropriate change in cell behavior.

A

effector proteins

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18
Q

he fundamental features of cell signaling have been conserved throughout the
evolution of the _____

A

eukaryotes

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19
Q

Expound the cell signaling in budding yeast

A

the response to mating factor depends on
* cell-surface receptor proteins
* intracellular GTP-binding proteins
* protein kinases

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20
Q

requires cells to be in direct membrane-membrane contact

A

Contact-dependent signaling

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21
Q

they are high specificity of binding site of receptors

A

target cells

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22
Q

Their extracellular domains may be released from the signaling cell’s surface by proteolytic cleavage and then act at a distance.

A

Transmembrane signal proteins

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23
Q

the target cell responds by means of a _____

A

receptor

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24
Q

binds the signal molecule and then initiates a response in the
target cell.

A

receptor

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25
Q

The binding site of the receptor has a complex structure that is shaped
to recognize the signal molecule with _____

A

high specificity

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26
Q

Binding of ECS Molecules: Most signal molecules are hydrophilic and are therefore unable to cross the target cell’s plasma membrane directly

A

cell-surface receptors

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27
Q

Some small signal molecules,
by contrast, diffuse across the plasma membrane and bind to receptor proteins inside the target cell

A

intracellular receptors

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28
Q

each cell is programmed to respond to ____ of extracellular signals

A

specific combinations

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29
Q

cell responds to the signals ____

A

selectively

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30
Q

if deprived of appropriate survival signals, a cell will undergo a form of cell suicide known as

A

apoptosis

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31
Q

a signal molecule often has __ __ on different types of target cell

A

different effects

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32
Q

the differences of the extracellular signal. why?

A

it simply induces the cell to respond according to its predetermined state, which depends on the cell’s developmental history and the specific genes it expresses.

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33
Q

three major classes of cell-surface receptor proteins

A

ion-channel coupled receptors
g-protein coupled receptors
enzyme-coupled receptors

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34
Q

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

A

signal transducers

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35
Q

Ion-channel-coupled receptors, also known as __ or __

A

transmitter-gated ion channels or ionotropic receptors

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36
Q

involved in rapid synaptic signaling between nerve cells and other electrically excitable target cells such as nerve and muscle cells

A

ion-channel-coupled receptors

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37
Q

Ion-channel-coupled receptors is mediated by _______

A

neurotransmitters opening or closing an ion channel

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38
Q

what happens in ion-channel receptors?

A
  • transmitter-gated ion
    channels or ionotropic
    receptors
  • electrically excitable cells
  • neurotransmitters
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39
Q

indirectly regulating the activity of a
separate plasma-membrane-bound target protein, which is generally either an enzyme or an ion channel.

A

G-protein-coupled receptors

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40
Q

mediates the interaction between the activated receptor and this target protein

A

trimeric GTP-binding protein (G protein)

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41
Q

how does G-proteins work?

A

can change the concentration of small intracellular signaling molecules OR change ion permeability

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42
Q

function as enzymes or associate directly with enzymes that they activate

A

enzyme-coupled receptors

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43
Q

enzyme-coupled receptors (5)

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

intracellular signaling molecules are small chemicals, which are often
called _______

A

second messengers

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45
Q

generated in large amounts in response to receptor activation and diffuses away from their source, spreading the signal to other parts of the cell.

A

second messengers

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46
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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47
Q

phosphorylation enzymes

A

protein kinase - on
protein phosphatase - off

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48
Q

2 types of protein kinase

A

serine/threonine kinase
tyrosine kinases

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49
Q

A protein kinase covalently adds a phosphate from ATP to the signaling protein, and a protein phosphatase removes the phosphate.

A

phosphorylation

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50
Q

induced to exchange its
bound GDP for GTP activates the protein; the protein then inactivates itself by hydrolyzing its bound GTP to GDP.

A

GTP-binding proteins

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51
Q

switches of GTP-binding proteins

A

GTP - on
GDP - off

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52
Q

2 types of GTP-binding proteins

A

trimeric GTP-binding proteins
monomeric GTP-binding
proteins

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53
Q

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

A

G-proteins

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54
Q

help relay signals from many classes of cell-surface receptors

A

small monomeric GTPases

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55
Q

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

A

GTPase-activating proteins (GAPs)

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56
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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57
Q

a sequence of two inhibitory steps can have the same effect as one activating step

A

double-negative activation

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58
Q

an activated intracellular signalling molecule should interact only with the appropriate __ __

A

downstream targets

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59
Q

2 characteristics of complementary surfaces

A

high affinity and specificity

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60
Q

The ability of downstream target proteins to simply ignore such signals respond only when the ___

A

upstream signal reaches a high concentration or activity
level

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61
Q

involves scaffold proteins

A

localization

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62
Q

holds the protein in close proximity;
interact at high local concentration;
sequentially activated rapidly

A

signaling complexes

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63
Q

phosphorylated cytoplasmic tail of the receptor serve as

A

Docking sites

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64
Q

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

A

Localization (scaffold proteins)

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65
Q

they can interact at high local concentrations and be sequentially activated rapidly, efficiently, and selectively in response to an appropriate extracellular signal

A

Scaffold proteins

66
Q

holds the protein in proximity; interact at high local concentration; sequentially activated rapidly

A

Signaling complexes

67
Q

form only transiently in response; around a receptor

A

Signaling complexes

68
Q

production of _____which recruit specific intracellular signaling proteins

A

Phosphoinositides

69
Q

Specialized behaviors that produce appropriate for the cell function that system controls (7)

A
  1. Response timing
  2. Sensitivity to extracellular signals
  3. Dynamic range
  4. Persistence
  5. Signal processing
  6. Integration
  7. Coordination
70
Q

Number or affinity; amplification

A

Sensitivity to extracellular signals

71
Q

Responsiveness

A

Dynamic range

72
Q

Transient response; prolonged or permanent

A

Persistence

73
Q

Switchlike response; oscillatory response

A

Signal processing

74
Q

Multiple inputs

A

Integration

75
Q

Multiple responses

A

Coordination

76
Q

speed of response depends on the nature of _____

A

intracellular signaling molecules

77
Q

Signaling if only changes in proteins already present in the cell (altered protein function)

A

Occurs rapidly: allosteric change in a neurotransmitter-gated ion channel

77
Q

changes in gene expression and the synthesis of new proteins (altered protein synthesis)

A

Occurs in minutes or hours, regardless of mode of signal delivery

78
Q

response fades when a _____

A

signal ceases

79
Q

2 types of abrupt responses when signal concentration rises beyond some threshold value

A

Sigmoidal
Discontinuous or all-or-none

80
Q

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

A

Sigmoidal response

81
Q

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

A

Discontinuous or all-or-none

82
Q

Smoothly graded response

A

hyperbolic

83
Q

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

A

feedback loops

84
Q

output stimulates its own production

A

Positive feedback

84
Q

output inhibits its own production

A

Negative feedback

85
Q
  • muscle-cell specification
  • all-or-none responses
  • all cells in a population do not respond identically to the same concentration of extracellular signal
A

Positive feedback

85
Q

steepen the response – sigmoidal or all-or-none response

A

Positive feedback

86
Q

Self-sustaining, bistable, can have switches

A

Positive feedback

87
Q

counteracts the effect of a stimulus
* limits the level of the response

A

Negative feedback

87
Q

In positive feedback, _____ can induce long
term changes in cells and their progeny that can persist for the lifetime of the
organism.

A

transient extracellular signal

88
Q

Delay in negative feedback

A

Oscillations

89
Q

respond to changes in the concentration of an extracellular signal molecule

A

Adaptations

90
Q

cells and organisms can detect the same percentage of change in a signal over a wide range of stimulus strengths

A

Adaptation or desensitization

91
Q

Some ways that the cell may adapt

A

Receptor sequestration
Down-regulation
Inactivation
Inactivation of signaling protein
Production of inhibitory protein

92
Q

largest family of cell-surface receptors, they mediate most responses to signals from the external world, as well as signals from other cells, including hormones, neurotransmitters, and local mediators.

A

G-protein-coupled receptors

93
Q

What senses depend on G-proteins?

A

Sight, smell. Taste

93
Q

Describe the structure of G-protein-coupled receptors

A

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

93
Q

it function is to couple the receptor to enzymes or ion channels in the membrane.

A

trimeric GTP-binding protein (G protein)

94
Q

3 protein subunits of G proteins

A

a, B, and y

94
Q

GTPase and becomes inactive when it hydrolyzes its bound GTP to GDP

A

GTPase Activating Proteins

94
Q

When a subunit has GDP bound and the G protein is inactive

A

Unstimulated and inactivated

95
Q

Activation of GPCR

A

acts like guanine nucleotide
exchange factor (GEF)

96
Q

Cyclic AMP is synthesized from ATP by an enzyme called

A

Adenylyl cyclase

96
Q

Sequence of signaling through G-protein-coupled receptors

A

Α subunit release its bound GDP →
binding of GTP →
conformational changes →
dissociation of the GTP bound Gα subunit from the Gβγ pair

96
Q

acts as a second messenger in some signaling pathways

A

Cyclic AMP

96
Q

c-AMP is continuously destroyed by

A

cyclic AMP phosphodiesterases

97
Q

stimulatory G protein activates adenylyl cyclase

A

Gs (stimulatory)

97
Q

What regulate the production of cyclic AMP

A

G-proteins

97
Q

What happens in pertussis toxin (whooping cough)

A

ADP ribosylation of the α subunit of Gi

98
Q

What happens in cholera toxin?

A

ADP ribosylation that alters the Gs α subunit

98
Q

Inhibitory of adenylyl cyclase

A

Gi (inhibitory)

98
Q

cAMP exerts its effects mainly by activating what? _____

A

cyclic-AMP dependent protein kinase (PKA)

98
Q

Adrenal cortex: Cortisol secretion

A

Adrenocorticotrophic hormone (ACTH)

98
Q

Ovary: Progesterone secretion

A

Luteinizing hormone (LH)

99
Q

Thyroid gland: thyroid hormone synthesis and secretion

A

Thyroid-stimulating hormone (TSH)

100
Q

Muscle: Glycogen breakdown

A

Adrenaline

101
Q

Bone resorption

A

Parathormone

101
Q

A specific transcription regulator called ______ recognizes this sequence

A

CRE-binding (CREB) protein

101
Q

Increase in heart rate and force of contraction

A

Adrenalin

101
Q

cAMP activates the gene that encodes the hormone ____

A

Somatostatin

101
Q

Glycogen breakdown in liver

A

glucagon

101
Q

[PI(4,5) P2]

A

phosphatidylinositol 4,5-bisphosphate

101
Q

Water absorption in kidney

A

Vasopressin

101
Q

PKA inactive state:

A

two catalytic subunits and two regulatory subunits

101
Q

PKA phosphorylates specific ___ and _____

A

Serines and threonines on target proteins

101
Q

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

A

CREB-binding protein (CBP)

101
Q

The activated phospholipase then cleaves the PI(4,5)P2 to generate two products:

A

inositol 1,4,5-trisphosphate (IP3) and diacylglycerol

101
Q

PKA activated state:

A

Released catalytic subunits

101
Q

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

A

cyclic AMP response element (CRE)

101
Q

CREB can transform a ___ cAMP signal into a ___-term change in a cell

A

Short, long

101
Q

What does diacyglyerol activates?

A

activate protein kinase C (PKC)

101
Q

Acts on inositol phospholipid signaling pathway

A

phospholipase C-β (PLCβ)

101
Q

G protein called ___ activates GEF (___) that activates a monomeric GTPase (Rho family) which regulates the actin cytoskeleton

A

G12
guanine nucleotide exchange factor

101
Q

Activates phospholipase C-B

A

Protein Gq

101
Q

Cite the process of IP3 activation

A

endoplasmic reticulum  IP3-gated Ca2+-release channels (IP3 receptors)  increases concentration of Ca2+ in the cytosol

101
Q

What are the specific GPCRs to recognize odors which acts through cAMP

A

Olfactory receptors

101
Q

What senses depend on GPCRs that regulate ion channels?

A

Smell and vision

102
Q

directly activate or inactivate ion channels in the plasma membrane of the target cell, thereby altering the ion permeability— and hence the electrical excitability—of the membrane.

A

G12 protein

102
Q

Example of G12 protein

A

Acetylcholine

102
Q

They activate an olfactory-specific G protein (known as Golf), which in turn activates ______

A

adenylyl cyclase

102
Q

How many olf receptors in human?

A

350

102
Q

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

A

Pheromones

102
Q

receptor activation stimulated by light causes ___ in the level of cyclic nucleotide

A

A fall

102
Q

stack of discs; contains cyclic-GMP-gated cation channels

A

phototransduction apparatus

102
Q

What is the crucial in vision? (clue: aside from cAMP)

A

Cyclic GMP

102
Q

continuous rapid synthesis

A

Guanylyl cyclase

102
Q

rapid degradation (by what enzyme?) controls the concentration of cyclic GMP in the cytosol

A

cyclic GMP phosphodiesterase

102
Q

responsible for noncolor vision in dim light

A

Rod photoreceptors (rods)

102
Q

responsible for color vision in bright light

A

cone photoreceptors (cones)

102
Q

___ bound to these channels keeps the rhodopsin open in the dark

A

Cyclic GMP

102
Q

In the light, it happens due to decreases the cyclic GMP conc. and closes the cation channel

A

Hyperpolarization

102
Q

It phosphorylates the cytosolic tail of activated rhodopsin on multiple serines

A

rhodopsin kinase (RK)

102
Q

activated by a photon of light

A

Rhodopsin

102
Q

The isomerization of all-trans retinal alters PROCESS

A

conformation of transducin (Gt) → activate the cyclic GMP phosphodiesterase →hydrolyzes cyclic GMP → GMP levels fall

102
Q

This hormone relaxes smooth muscles in the walls of blood vessels

A

Nitric oxide (NO)

102
Q

Inhibits rhodopsin kinase (RK)

A

Arrestin

103
Q

What stimulates NO synthesis?

A

acetylcholine

104
Q

diffuses out of the cell into neighboring smooth muscle cells

A

Nitric Oxide (NO)

105
Q

GPCRs 3 modes of adaptation

A
  1. receptor sequestration
  2. receptor down-regulation
  3. receptor inactivation
106
Q
  • prevents the activated receptor from interacting with G proteins * adaptor protein
A

Arrestin desensitization

AAA BIO107: Cell and Molecular Biology (5 decks)

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