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Comprehensive Exam > Cell Signaling > Flashcards

Cell Signaling Flashcards

1
Q

What occurs in the cell after the arrival of a signal?

A
  • Receptors perceive the signal
  • Receptor transmits the signal into the cell
  • Message is past along in a cell signaling cascade
  • Message arrives at final destination
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2
Q

What makes a good signal?

A

Signals must have specificity as to only relay a certain message and not relay others; must be small (usually); needs to be able to be manufactured quickly; readily reversible; must be able to get from point of manufacturing to cell receptor

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3
Q

How can signals be conveyed?

A
  • Electrical potential changes (synaptic signalling) - axon terminal to axon to cell body to dendrites to synapses to next cell
  • Endocrine - signal released by one cell and sent to be received at a cell far away
  • Paracrine - signal released by one cell and sent locally
  • Autocrine - signal released to affect the same cell that produced the signal
  • Direct cell-cell signaling - cells in physical contact with each other share through these contacts
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4
Q

What is a ligand?

A

any molecule that binds to specific sites on a protein

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5
Q

What are methods of direct cell-cell signaling?

A

Receptor-ligand signaling - ligand binds to the receptor
Gap junctions and plasmodesmata - pores between cells allow exchange of small chemicals
Protein-protein interactions

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6
Q

What is convergence and divergence in cell signaling?

A

Diverge - one signal causes multiple reactions

Converge - multiple signals can cause same reaction

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7
Q

What is amplification?

A

A small amount of signaling molecule produces a great response in a cell

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8
Q

What are second messengers?

A

The signaling molecules produced by the cell after the initial signal has been received

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9
Q

What is a signal transduction pathway?

A

the arrangement of components that carry the message to its final destination

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10
Q

What are some types of molecules involved in signal transduction pathways?

A

hormones, proteins, lipids, nucleotides

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11
Q

What are some technologies used in signaling studies?

A 
Antibodies
Fluorescent probes
Confocal microscopy
Biochemical approaches
Gene sequence analysis
Microarray analysis
Proteomics
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12
Q

What are hormones?

A

diverse group of molecules, small and water soluble peptides or lipophilic molecules; detected by cell surface receptor or intracellular receptor

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13
Q

What are cytokines?

A

group of peptides that include interleukins, interferons, and tumor necrosis factors; orchestrate immune responses and host defense

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14
Q

What are chemokines?

A

large group of extracellular signals controlling the immune system; two families

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15
Q

What are growth factors?

A

molecules that are involved with the regulation of growth and differentiation

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16
Q

What are receptors?

A

Proteins whose purpose is to detect extracellular signals and transmit these signals into the cell; generally found on plasma membrane

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17
Q

What are steroid receptors?

A

Receptors found within the cell; the ligand goes through the plasma membrane to reach it

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18
Q

What types of receptor are there?

A
  1. G-protein-coupled receptors - activate G proteins
  2. Ion channels linked receptors - change ion movements across the membrane
  3. Receptors that contain intrinsic enzyme activity
  4. Receptors that recruit separate enzymes
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19
Q

How can a cell change its sensitivity to a cell signal?

A

Cells can change the number of receptors present on the outer side of the cell surface (internalization and endocytosis or creation of new receptors)

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20
Q

What is phosphorylation?

A

A common process in signaling pathways; addition of one or more phosphoryl groups to certain amino acid side groups on a polypeptide change

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21
Q

What is dephosphorylation?

A

The removal of one or more phosphoryl groups from certain amino acid side groups on a polypeptide chain

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22
Q

What enzymes add phosphoryl groups to the amino acid side chains? Which remove them?

A

Kinases - add

Phosphatases - remove

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23
Q

What two types of phosphorylation events are there?

A

Serine/threonine phosphorylation

Tyrosine phosphoryation

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24
Q

What are types of serine/threonine kinases?

A

Protein kinase C, cAMP-dependent protein kinase, Calcium/calmodulin protein kinase, cGMP-dependent protein kinase

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25
Q

How does a cAMP-dependent protein kinase work?

A

Inactive; on activation it dissociates; when bound to cAMP, two catalytic subunits are released

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26
Q

How do protein kinase Cs work?

A

Calcium ion concentrations activate the protein kinase (usually)

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27
Q

How do calcium/calmodulin-dependent kinases work?

A

Activated by calcium ions

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28
Q

How do tyrosine kinases generally work?

A

Membrane-bound receptors, bind to the ligand through autophosphoyration and then phosphorylates with intracellular proteins

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29
Q

How do MAP kinases work?

A

Sequential kinases; receptor binds to growth factor, insulin, or G protein to begin pathway

30
Q

What are histine kinases?

A

Histine kinases are found mostly in prokaryotes an a phosphoryl group attaches to histidine and aspartate

31
Q

What two groups do phosphatases belong to?

A

Serine/threonine

Tyrosine

32
Q

What are some types of cyclic nucleotides? What do they do?

A

cAMP and cGMP; central signaling molecules in transduction pathways

33
Q

How is cAMP made?

A

Produced from ATP by the enzyme adenylyl cyclase

34
Q

How does heterotrimeric G proteins work?

A

Constructed wit ha beta/gamma complex and an alpha subunit that binds to GDP in an inactive state and GTP in its active state

35
Q

How is cGMP made?

A

Produced by the enzyme guanylyl cyclase in one of two forms - soluble or membrane bound

36
Q

How does cyclic nucleotide signaling end?

A

Hydrolysis of cyclic forms to the monophosphate forms by phosphodiesteres enzymes

37
Q

How do monomeric G proteins work?

A

When bound to GTP, active; hydrolyzed to GDP to return to inactive state

38
Q

What are monomeric G proteins used for?

A

transduction of signals for growth factors and kinases; alter activity in nuclei

39
Q

How does the breakdown of lips in the plasma membrane aid in cell signaling?

A

Part of the pathway, formation of messenger molecules in the cell follows

40
Q

What are inositol phosphates?

A

Part of many cells signaling cascades; easily phosphorylated or dephosphorylated

41
Q

What are calcium ions?

A

Unusual signaling molecules; not created or destroyed; signaling results from rapid change of distribution

42
Q

How do calcium ions affect cell signaling?

A

Usually pumped out of the cell through pumps on the plasma membrane or stored in various organelles; when cytoplasmic calcium suddenly rises by a release from an internal organelle, allow for calcium to bind to calcium-binding proteins

43
Q

What do calcium ions affect?

A

Regulation of protein kinase C, cell cycles, calcium/calmodulin-dependent protein kinases, signaling routes, metabolic enzymes

44
Q

What types of signaling molecules work in paracrine and autocrine signaling?

A

small inorganic molecules of nitric oxide, superoxide ions, hydrogen peroxide, and carbon dioxide

45
Q

How is nitric oxide produced?

A

Nitric acid synthase enzyme works in tangent with arginine as a substrate; xanthine oxidoreductase; nitrate reductase

46
Q

How does nitric oxide signaling work?

A

Controls cGMP production through guanylyl cyclase [include nitrosylation and oxidation of proteins]

47
Q

How are oxygen free radicals produced?

A

Electron leakage of electron transport chains; enzyme NADPH oxidase

48
Q

What role does superoxide play?

A

Kill invading pathogens

49
Q

What role do reactive oxygen species play?

A

Control cellular proliferation, rates of transcription (via direct action or through MAP kinase pathways)

50
Q

What role does insulin play in cell functioning?

A

Metabolic pathways, stimulation of protein translocation, control gene expression

51
Q

How is insulin created?

A

two peptide chains held together by disulphide bonds, hydrogen bonds, and salt bridges; made by cells of the islets of Langerhans of the pancreas as a single gene product and then modified by cleavage

52
Q

How is insulin detected?

A

Insulin receptors (growth factors); two alpha and two beta subunits with alpha on the outside to receive insulin and beta on the transmembrane domain with tyrosine kinase domains

53
Q

How does insulin receptors work?

A

After binding, autophosphorylation of tyrosine residues and other proteins, activating other proteins

54
Q

How can insulin signaling be deactivated?

A

Internalizing the receptor which can be recycled back; dephosphorylation of proteins too

55
Q

What does the perception of the environment have to do with cell signaling?

A

Perception is important; response to environmental factors (such as light and chemicals) use signaling pathways

56
Q

What type of receptors do plants have for light?

A

Phytochromes and light receptors

57
Q

What purpose do cells have for detecting chemicals?

A

Prokaryotes sense vital nutrients

Multicellular organisms - detect as small or taste

58
Q

Hod does cell signaling relate to gene expression?

A

Signal transduction pathways lead to transcription factors in the nucleus
Transcription factors controlled by phosphorylation and oxidation

59
Q

What is notch signaling?

A

Allow cells to have direct cell-cell communication

60
Q

What is hedgehog signaling?

A

Developmental signaling; perceived by a system with Patched and Smoothened proteins with an end result to influence activity of Cubitis interruptis protein

61
Q

What is Wnt signaling?

A

Perceived by proteins Frizzled and LRP to release beta-catenin into the cytoplasm to be moved to act on transcription factors in the nucleus

62
Q

What are Toll-like receptors?

A

Used in immune response and perceived by pathogen-derived molecules

63
Q

What is apoptosis?

A

Programmed cell death used for development and body maintenance

64
Q

What pathways lead to apoptosis?

A

Intrinsic - release of proteins (cytochrome c, apoptosis-inducing factor, endonuclease G) from mitochondria
extrinsic - death receptors at plasma membrane with cysteine-rich domains

65
Q

What are caspases?

A

Cysteine proteases (active cysteine) that mediate morphological changes during apoptosis; cleave other proteins at C-terminal of aspartic acid residue; activated by protein-cleavage events; tetrameric structure with two large and two small subunits

66
Q

What are apoptosomes?

A

Complexes of cyctochrome c, apoptotic protease-activating factor, and caspase-9

67
Q

What are death-inducing signaling complexes?

A

death domains and dead effector domains, the death receptor, adaptor proteins, and initiator caspases; lead to caspase cleavage and apoptosis; modulated by the presence of decoy receptors or Flice-like inhibitory proteins

68
Q

How many times does a G-protein coupled receptors pass through the membrane?

A

7

69
Q

What type of cell signaling is used for testosterone and estrogen?

A

Steroid hormone binding

70
Q

How does steroid cell signaling work?

A

Lipophilic hormones are insoluble in water, so they are passed in the bloodstream in carrier proteins. Once they arrive at the destination, dissociation of the proteins allow the hormone to pass through the plasma membrane and into the cell, where it binds to an internal receptor.

Comprehensive Exam (6 decks)

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