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Cell and Molecular Biology > Module 5 Cell Signaling: 1 Principles of Cell Signaling > Flashcards

Module 5 Cell Signaling: 1 Principles of Cell Signaling Flashcards

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1
Q

It’s a process by which cells respond to physical and chemical changes in their environment through mechanisms that allow them to communicate with each other.

A

Cell signaling

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2
Q

It’s a process where bacteria secrete chemical signals to coordinate behavior, such as motility, antibiotic production, and spore formation, based on population density.

A

quorum sensing

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3
Q

Yeast cells secrete a __ that signals opposite mating-type cells to stop proliferating and prepare for mating, leading to zygote formation.

A

mating factor peptide

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4
Q

These are molecules that communicate signals between cells, including proteins, peptides, amino acids, nucleotides, steroids, and gases like nitric oxide and carbon monoxide.

A

extracellular signal molecules

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5
Q

an extracellular signal molecule that binds specifically to a receptor to initiate a cellular response.

A

ligand

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6
Q

cells produce signals that they themselves respond to.

A

autocrine signaling

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7
Q

occurs in neurons, where chemical synapses allow neurotransmitter release to communicate with target cells.

A

synaptic signaling

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8
Q

uses hormones released into the bloodstream to target distant cells throughout the body.

A

endocrine signaling

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9
Q

a protein, often a transmembrane protein, that specifically binds to a ligand and initiates an intracellular signaling cascade.

A

receptor protein

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10
Q

the final targets in signaling pathways, which are altered by the signal to bring about a change in cell behavior, such as gene expression or ion channel activity.

A

effector proteins

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11
Q

Each cell is programmed to respond to specific combinations of extracellular signals that may __ or __ different cellular actions.

A
  • stimulate
  • inhibit
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12
Q

Cells respond selectively to certain signals, ensuring that they integrate relevant signaling information to make specific decisions, such as when to divide, move, or differentiate.

A

Signal selectivity

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13
Q

Cells integrate multiple signaling inputs to determine appropriate responses, which may include __, __, __, or __(__).

A
  • division
  • movement
  • differentiation
  • programmed cell death (apoptosis)
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14
Q

the programmed death of a cell, which is a controlled process essential for removing damaged or unnecessary cells.

A

Apoptosis

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15
Q

the process by which cells divide and multiply, essential for growth, tissue repair, and regeneration.

A

Cell proliferation

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16
Q

the final stage of cell differentiation, where a cell becomes specialized to perform a specific function and typically loses its ability to divide.

A

Terminal differentiation

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17
Q

A signal molecule can have varied effects on different target cells due to differences in their __, __, and __.

A
  • intracellular signaling proteins
  • effector proteins
  • gene expression
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18
Q

An example of a signal molecule that can elicit different responses in various target cells and give three (3) target cells and its response.

A

Acetylcholine
- heart pacemaker cell > decreased heart rate of firing
- salivary gland cell > secretion
- skeletal muscle cell > contraction

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19
Q

A __ can have varied effects on different target cells due to differences in their intracellular signaling proteins, effector proteins, and gene expression.

A

signal molecule

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20
Q

The response of a target cell to a signal molecule is guided by its __, meaning that it will react according to its specific cellular context and signaling pathways.

A

predetermined state

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21
Q

What are the three major classes of cell-surface receptor proteins? (3)

A
  • ion-coupled-channel receptors
  • G-protein coupled receptors
  • enzyme-coupled receptors
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22
Q

__ proteins act as signal transducers, converting an extracellular ligand-binding event into intracellular signals that alter the behavior of the target cell.

A

Cell-surface receptor

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23
Q

What are ion-channel coupled receptors also known as? (2)

A

transmitter-gated ion channels or ionotropic receptors

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24
Q

__ cells, such as neurons and muscle cells, commonly utilize ion-channel coupled receptors.

A

Electrically excitable

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25
Q

Neurotransmitters bind to __, causing the channels to open and allowing ions to flow across the cell membrane, thus altering the cell’s electrical potential.

A

ion-channel coupled receptors

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26
Q

a cell-surface receptor protein that activates plasma-membrane-bound target proteins, such as enzymes or ion channels, through the intermediary of a trimeric GTP-binding protein (G protein).

A

G-protein-coupled receptors (GPCRs)

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27
Q

G-protein-coupled receptors (GPCRs) activate plasma-membrane-bound target proteins, such as enzymes or ion channels, through the intermediary of a __.

A

trimeric GTP-binding protein (G protein).

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28
Q
  • a cell-surface receptor protein that functions as enzymes themselves or are directly associated with enzymes that they activate upon ligand binding.
  • typically single-pass transmembrane proteins, with ligand-binding sites located outside the cell and enzyme-binding sites inside the cell.
A

Enzyme-coupled receptors

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29
Q

__ are enzymes that catalyze the transfer of phosphate groups to specific substrates, thereby modifying the activity of proteins and playing a crucial role in signaling pathways.

A

Protein kinases

30
Q

molecules that are often referred to as second messengers.

A

Intracellular signaling

31
Q
  • typically small chemicals or water-soluble molecules, or lipid-soluble, that bind to and alter the behavior of selected signaling or effector proteins.
  • act as molecular switches by changing their state or concentration, which influences the activity of downstream signaling proteins.
A

Second messengers

32
Q

the addition of a phosphate group to a protein, typically carried out by kinases, which can activate or deactivate the protein’s function.

A

phosphorylation

33
Q

What types of kinases are involved in phosphorylation? (2)

A
  • serine-threonine kinases
  • tyrosine kinases
34
Q

__ remove phosphate groups from proteins, reversing the effects of kinases and thus modulating protein activity.

A

Phosphatases

35
Q

How many kinases and phosphatases are present in human cells?

A
  • 520 kinases
  • 150 phosphatases
36
Q

GTP-binding proteins are in the “__” state when bound to GTP and in the “__” state when bound to GDP.

A
  • on/active
  • off/inactive
37
Q

What are the two types of GTP-binding proteins?

A
  • trimeric GTP-binding proteins (G proteins)
  • monomeric GTP-binding proteins (small monomeric GTPases).
38
Q

activate the “off” state by promoting the hydrolysis of GTP to GDP.

A

GTPase-activating proteins (GAPs)

39
Q

activate GTP-binding proteins by releasing bound GDP, allowing GTP to bind and switch the protein to the “on” state.

A

Guanine nucleotide exchange factors (GEFs)

40
Q

refers to a series of activation steps where the inhibition of a negative regulator leads to the activation of a signaling pathway.

A

Double-negative activation

41
Q

An activated intracellular signaling molecule should interact only with appropriate downstream targets, ensuring __ and __ for effective signaling.

A
  • high affinity
  • specificity
42
Q

can ignore signals unless the upstream signal reaches a high concentration or activity level, allowing for precise regulation of cellular responses.

A

Downstream target proteins

43
Q

What are the three types of intracellular signaling complexes?

A
  • Performed signaling complex on a scaffold protein
  • Assembly of signaling complex on an activated receptor
  • Assembly of signaling complex on a phosphoinositide docking sites
44
Q

localize signaling proteins into complexes, enhancing specificity and reducing background noise by holding them in close proximity for rapid interaction.

A

Scaffold proteins

45
Q
  • hold proteins at high local concentrations, allowing for rapid, efficient, and selective activation in response to extracellular signals.
  • often form transiently in response to an extracellular signal and rapidly disassemble when the signal is gone.
A

Signaling complexes

46
Q

The __ of an activated enzyme-coupled receptor is phosphorylated, creating docking sites for other signaling proteins to assemble.

A

cytoplasmic tail

47
Q

modified phospholipid molecules produced upon receptor activation that recruit specific intracellular signaling proteins to the membrane for activation.

A

Phosphoinositides

48
Q

What are the key features of an effective signaling response in terms of timing and sensitivity? (7)

A
  1. response timing
  2. sensitivity to extracellular signals (through number or affinity and amplification)
  3. dynamic range (responsiveness)
  4. persistence (transient response; prolonged or permanent)
  5. signal processing (switchlike response; oscillatory response)
  6. integration of multiple inputs
  7. coordination of multiple responses.
49
Q

The speed of __ is influenced by whether the changes involve rapid alterations in existing proteins or slower changes in gene expression and new protein synthesis.

A

response

50
Q

The __ of the cell typically fades when the signaling molecule is no longer present, highlighting the transient nature of many signaling pathways.

A

response

51
Q

refer to the series of signals or processes that occur within a cell after an initial signaling event. These signals are the result of the activation of signaling pathways following the binding of an extracellular signal (such as a hormone, neurotransmitter, or growth factor) to a receptor on the cell surface.

A

downstream signals

52
Q

What type of response is characterized by a smoothly graded reaction as the concentration of a signaling molecule increases?

A

Hyperbolic response

53
Q

What occurs when the concentration of a signaling molecule rises beyond a certain threshold value?

A

Abrupt responses occur

54
Q

What type of response curve shows a gradual increase in response at low concentrations, a steeper increase at intermediate concentrations, and a plateau at high concentrations?

A

Sigmoidal response

55
Q

A discontinuous or switch-like response where the cell completely switches between low and high response levels.

A

all-or-none response

56
Q

Rapid responses occur when existing __ change, while responses involving __ and new __ take longer (minutes to hours).

A
  • proteins
  • gene expression
  • protein synthesis
57
Q

What happens to a signaling pathway when the extracellular signal is withdrawn?

A

The response often fades, especially if it depends on short-lived intracellular molecules.

58
Q

mechanisms where the output of a process regulates that same process.

A

Feedback loops

59
Q

A feedback that occurs when the output stimulates its own production, enhancing the response.

A

Positive feedback

60
Q

How does positive feedback affect the response curve?

A

It can steepen the response, resulting in sigmoidal or all-or-none responses.

61
Q

What does it mean for a system to be bistable in the context of positive feedback?

A

can exist in either a “switched-off” or a “switched-on” state, often becoming self-sustaining after activation.

62
Q

It can induce long-term changes in cells, such as muscle-cell specification, which can persist beyond the initial signal.

signal

A

transient extracellular signal

63
Q

A feedback that makes the system less sensitive to perturbations by abbreviating and limiting responses.

A

negative feedback

64
Q

What is the effect of long delays in negative feedback?

A

Long delays can produce oscillatory responses that may persist as long as the stimulus is present.

65
Q

In the context of negative feedback, this occurs when a system generates a brief response to a stimulus that quickly decays, even while the stimulus persists.

A

Adaptation

66
Q

the process where prolonged exposure to a stimulus decreases the cell’s response to that level of stimulus.

A

Adaptation or desensitization

67
Q

Prolonged exposure to stimulus modifies the signaling machinery, resetting it to become __ responsive to that stimulus.

A

less

68
Q

A strong response can lead to modifications in the signaling machinery that results in decreased __ to the same stimulus.

A
  • sensitivity
69
Q

Cells can adjust their responsiveness based on the __ of the extracellular signal molecule, which may involve adaptation.

A

concentration

70
Q

It prevents overstimulation and allows cells to fine-tune their responses to fluctuating levels of signals.

A

desentization

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