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Biology > Chapter 16: Cell Signaling > Flashcards

Chapter 16: Cell Signaling Flashcards

1
Q

What is signal transduction

A

process of converting one type of signal to another

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2
Q

What are agonist?

A

Signal molecules that activates receptors

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3
Q

What are antagonist?

A

Signal molecules that block receptor activity

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4
Q

How are signal molecule detected by a target cell?

A

Receptor proteins (receptors)

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5
Q

What are the 5 types of cell communication

A
  1. Endocrine
  2. Paracrine
  3. Synaptic
  4. Contact-Dependent
  5. Autocrine
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6
Q

What is long distance, wide distribution cell communication?

A

Signal sent over long distance throughout the whole body

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7
Q

What type of communication uses with long distance wide distribution

A

Endocrine

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8
Q

What are the signaling molecules associated with long distance wide distribution?

A

Hormones

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9
Q

What does hormones do?

A

Extracellular signaling molecules that mediate endocrine signaling made by endocrine cells

Ex: Insulin

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10
Q

What type of communication uses short distance, local distribution

A
  1. Paracrine
  2. Autocrine
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11
Q

What is short distance local distribution

A

Signal molecules diffuse locally instead of going into the blood streams

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12
Q

What signaling molecule carry out short distance local distribution

A
  1. Local mediator
  2. Autocrine signaling
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13
Q

What is local mediator?

A

Extracellular signaling molecules that mediate paracrine signaling

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14
Q

What is autocrine signaling?

A

Type of autocrine signaling in which cells responds to local mediator that they themselves produce

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15
Q

What is the difference between endocrine and paracrine/autocrine signaling

A

The distance

Paracrine: signal spread and lifetime will be shorter, which affects the local area

Endocrine: signal spread over the whole body

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16
Q

What is synaptic communication?

A

A long distance, cell specific communication in which message is delivered over long distance, but to a specific recipients not widely like hormones

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17
Q

What type of communication uses long distance cell specific

A

Synaptic

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18
Q

What contributes to long distance cell specific communication

A
  1. Synapse
  2. Neurotranmitter
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19
Q

What is a synpase?

A

junction between axon of one neuron and dendrites of another neuron where information is transferred

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20
Q

What are neurotransmitters?

A

Signaling molecules released from axons at the synapse

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21
Q

What type of communication uses cell-cell specific

A

Contact Dependent

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22
Q

What is contact dependent communication?

A

A cell-cell specific communication in which membrane bound signal molecules bind to membrane receptors

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23
Q

How does contact dependent communication work?

A

Cell make direct physical contact to the target cell’s receptors

Delta and Notch

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24
Q

If cells are exposed to multiple signaling molecule, How do they know which signal to respond?

A

Each cell respond to a limited set because their receptor is specific, thus production of limited set of receptor allow a cell to restrict the numbers of signal that can affect it

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25
Q

Where are the two location receptors can be located on the cell?

A
  1. On the cell’s surface (cell surface)
  2. In the cell (intracellular)
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26
Q

What determines the response of the cell to a particular signal?

A

A cell’s intracellular relay system

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27
Q

How is it possible that the same signal can evoke different response?

A

Cells have different type of receptors/ intracellular relay proteins

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28
Q

Why is combinatorial control so crucial to cell?

A

Cell needs a combination of signal molecule for it to regulate the cell’s behavior. If the cell is deprived from its necessary signal, it will undergo apoptosis

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29
Q

What are the 5 components of intracellular signaling pathway

A
  1. Relay the signal onward
  2. Amplify the signal
  3. Integrate more than one
    extracellular signal
  4. Distribute the signal to more
    than one effector protein
  5. Modulate the response by
    feedback
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30
Q

How can intracellular signaling protein act as molecular switches?

A

Positive Feedback and Negative Feedback

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31
Q

What are the two main molecular switches that regulate signaling cascade?

A
  1. Protein Phosphorylation
  2. GTP binding protein
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32
Q

Describe protein phosphorylation

A

Attaching a phosphate group to an amino acid: serine, theronine, or tyrosine using kinase and dephosphorylation using phosphatase, stimulating or inhibiting protein activity

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33
Q

What is the result of protein phosphorylation

A

Phosphorylation cascade: Because protein switch can act as kinase, one kinase can phosphorylates the next kinase in the sequence, and so on, transmitting the signal onward and, in the process, amplifying, distributing, and regulating it

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34
Q

What are the three amino acids that are phosphorylated

A

Serine/Threonine and Tyrosine

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35
Q

Describe GTP binding protein

A

A protein bind to GTP will be activated while protein bind to GDP will be inactivated

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36
Q

What are the proteins that add/remove GTP

A

Guanine nucleotide Exchange Factor (GEF)

GTPase activating protein (GAP)

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37
Q

What does GEF do?

A

promote exchange from GDP to GTP, activating the protein

38
Q

What does GAP do

A

Promote GTP hydrolysis, deactivating the protein

39
Q

What is receptor down regulation

A

decrease in total receptor number in the cell

40
Q

What causes receptor down regulation

A

1.ligand binds to receptor

  1. ligand/ receptor complex is endocytosed
  2. after chronic receptor stimulation, receptor
    levels fall, resulting in desensitization; degration of receptor from overused by agonist
41
Q

What are the three type of cell surface receptors?

A
  1. Ion channel coupled receptors
  2. G Protein coupled receptor
  3. Enzyme coupled receptor
42
Q

What is ion channel coupled receptors

A

Receptors, in the form of gated ion channel, that convert a chemical signal into an electrical signal

43
Q

What is G protein coupled receptors (GPCR)

A

7 transmembrane domains receptors in eukaryotes.

44
Q

What does GPCR do?

A

Mediate responses to a diverse signals hormones, local mediators, neurotransmitters

45
Q

What happens when an extracellular signal bind to GPCR

A

It undergoes a conformational change that enables it to activate a G protein

46
Q

How does G Protein get activated and what happens when it activates

A

G protein are activated whenever an extracellular signal bind to GPCR. This caused the α subunit to be less affinitive for GDP, exchanging the molecule for GTP, activating it.

47
Q

Describe the structure of G protein

A

There are alpha, beta, and gamma subunit, in which the alpha and gama subunit is tethered to the membrane by lipid tails.

48
Q

What are the member of G alpha protein

A

G alpha S

G alpha I

G alpha q

49
Q

What happens when G alpha S is activated

A

Stimulation of adenylyl cyclase

50
Q

What happens when G alpha I is activated

A

Inhibition of adenylyl cyclase

51
Q

What happens when G alpha q is activated?

A

stimulates release of calcium from intracellular store,

52
Q

What is the trimeric G protein

A

G protein that has alpha, β,γ subunit

53
Q

Describe the process whenever GPCR is activated

A
  1. Ligand binds to GPCR, causing a conformational change that allow interaction with the trimeric-G-protein
  2. The alteration ofthe α subunit of the G protein allows it to exchange its GDP for GTP.
  3. G protein alpha subunit dissociate with the G protein βγ subunit because of the conformational change
  4. Signal transduction ends when Gα hydrolyzes its GTP, becomes GDP bound and reassociates with Gβγ
54
Q

How is G protein inactivated

A

GTP hydrolysis by G alpha subunit hydrolyzing its GTP so it can reassociate with the βγ unit

55
Q

How does the alpha subunit of G protein reassociate with its beta/gamma subunit?

A

It can hydrolyze its own GTP, deactivating it so it can reassociated

56
Q

How can some G protein activate ion channel?

A

1.. Acetylcholine binds to GPCR

  1. G protein is activated and alpha subunit separate from βγ subunit.
  2. βγ subunit open K+ channel by increasing its permeability to K+.

Inactivated of αlpha subunit by hydrolysis of its bound GTP returns G protein to its original state, allowing K+ to close.

57
Q

How can G protein trigger the synthesis or release of second messenger molecule?

A

Activation of G α subunit caused the Gαs to be stimulated, causing a stimulation of adenylyl cyclase, producing cyclic AMP,

and phospholipase C which produce inositol trisphosphate and diacylglycerol, ultimately producing Ca 2+

Activation of G alpha a - > adenylyl cyclase -> cyclic AMP binds to PKA

Activation of G alpha q -> P3/DAG -> Ca 2+

58
Q

What is the primary target of cyclic AMP?

A

Protein Kinase A (pka)

59
Q

Describe the pathway that shows how glycogen breakdown is activated

A
  1. Epinephrine binds to GPCR
  2. G alpha s is activates
  3. Adenylyl Cyclase is produced
  4. cAMP is produced
  5. cAMP binds to pka
  6. pKA phosphorylation promote glycogen breakdown
60
Q

Describe the pathway that shows how transcription of proteins involved in learning is activated

A
  1. cAMP binds to PKA
  2. PKA enter nucleus
  3. PKA phosphorylate transcription regulator
  4. Target gene is transcribed
61
Q

What happens when signaling molecule acts through Gαq?

A

Phospholipase C is activated instead of adenylyl cyclase.

62
Q

What does phospholipase C do?

A

cleaves an inositol phospholipid that is embedded in the
cytoplasmic face of the plasma membrane to generate two second-messenger
molecules: IP3 and DAG

63
Q

What are the two molecules that results from the cleavage of inositol phospholipid?

A

Inositol trisphosphate (IP3)- diffuse in cytosol
Diacylglycerol (DAG)- remain in membrane

64
Q

What does IP3 do after its production?

A

binds to and opens calcium channels in the ER

65
Q

What happens to Diacylglycero after its production

A

remains embedded in the plasma membrane and help recruit and activate PKC alongside with calcium

66
Q

How is protein kinase C (PKC) activated?

A

By the DAG that is on the membrane and the calcium that were release from IP3 opening the channel

67
Q

How can calcium serve as a second messenger molecule?

A
  1. stimulates cell responses by binding to and
    influencing Ca2+ binding protein
  2. activates NOS to generate NO and cGMP
    signaling to dilate blood vessels
68
Q

What happens when calcium binds to calmodulin?

A

Calmodulin undergoes a conformational change that allows it to bind it
Ca2+/calmodulin-dependent protein
kinase (CaM-kinase)

69
Q

What can CaM-Kinase do after its production?

A

It can bind to Ca2+/calmodulin-dependent protein
kinase (CaM-kinase) , which can phosphorylate its target

Ex: important part in some forms of learning and
memory in mammalian brain

70
Q

What happens when Calcium activates Nitric Oxide Synthase (NOS)?

A

Nitric Oxide (NO) and cyclic GMP (cGMP) is generated signaling to dilate blood vessels

NO binds to guanylyl cyclase to make cGMP

71
Q

Describe the process of how muscle is relaxed in the cell wall

A
  1. neurotransmitter acetylcholine causes the blood vessel to dilate by binding to a GPCR
  2. G protein, Gq, is activated
  3. Calcium is released from the opening of ion gated channel from the beta-gamma subuit
  4. Ca2+ activates nitric oxide synthase (NOS), stimulating the production of NO
  5. NO then diffuses out of the endothelial cells, causing muscle cell to relax
72
Q

Give an example on how intracellular signaling can adapt or amplify a signal

A

response of the eye to light

  1. light is sensed by rhodopsin, a G-protein-coupled light receptor.
  2. Rhodopsin activates a G protein called transducin.
  3. Transducin activates a signaling cascade
  4. Signaling cascade causes cation channels to close producing change in membrane potential and altered neurotransmitter release
  5. Signal is relayed to brain
73
Q

Why do cells have evolved intracellular calcium store for signaling even though there is abundant extracellular calcium.

A

The rapid clearing of Ca2+ ions from the cytosol by Ca2+ pumps prevents Ca2+ from diffusing any significant distance in the cytosol.

74
Q

Contrast enzyme couple receptor and GCPR

A

GPCR associate with G protein. Cytoplasmic domain acts as an enzyme or form a complex with another protein that acts as an enzyme

75
Q

Describe the activation of process of enzyme couple receptors

A
  1. Binding of signal causes two Receptor tyrosine kinases (RTK) receptors to dimerize – leading to enzyme activation
  2. The two intracellular tails of the receptors come together, activating their kinase domain
  3. The tails phosphorylate together and the tails serves as docking sites
  4. RTKs transmit signals simultaneously to multiple destinations, causing activation of downstream signaling pathway
76
Q

How does the RTK return to its inactive state?

A
  1. tyrosine phosphatases remove the phosphates that were added
  2. RTK undergo endocytosis and are destroyed by lysosome
77
Q

What is ras?

A

a small GTP-binding protein that is activated by RTK

78
Q

What happens after ras is activated?

A

RTK is phosphorylated and recruits Ras GEF

  1. GEF activates MAP kinase kinase kinase
  2. MAP kinase kinase kinase activates MAP kinase kinase
  3. MAP kinase kinase activates MAP kinase
  4. Changes in protein activity and gene expression
79
Q

What are the two consequences of activation of RTK

A
  1. Ras Activation
  2. PI3 Activation
80
Q

What happens when PI3 is activated?

A

Promote membrane docking and activates AKT

81
Q

What is AKT and what does it do

A

Protein kinase B

promotes growth and survival of cell type by inactivating the signaling proteins it phosphorylates.

  1. Inactivate Bad
  2. Activate Tor
82
Q

What does AKT inactivate

A

Bad - an apoptosis promoter

83
Q

What does AKT activate

A

Tor - a protein that stimulates cell growth
by inhibiting protein degradation and stimulating
protein synthesis

84
Q

Describe the process that leads to AKT promoting cell growth

A
  1. RTK is activated
  2. IP3 is activated
  3. IP3 sends signal to AKT
  4. AKT phosphorylate Bad and Activate Tor

Bcl2 inhibits apoptosis and Tor inhibits protein degration

85
Q

What is notch?

A

receptor that controls the development of neural cells in Drosophila

86
Q

What happens when notch binds to delta?

A

the notch receptor is cleaved releasing the cytosolic tail of the receptor, which is then free to move to the nucleus, where it helps to activate the appropriate set of Notch-responsive genes

87
Q

What are the two ways signaling molecule can cross the plasma membrane?

A
  1. Direct activation of an intracellular enzyme.
  2. Bind to intracellular receptors.
88
Q

How does steroid hormones cross the plasma membrane?

A

uses Intracellular receptors

  1. Nuclear receptor binds to steroid hormones
  2. receptor-cortisol complex move into nucleus
  3. complex binds to regulatory region of target gene to activate transcription
89
Q

Compare and Contrast plant and mammalian signaling

A

Plant cells don’t use RTKs, steroid-hormone type nuclear
receptors, cAMP, and have few GPCRs. They use ethylene instead to regulate their function

90
Q

Describe the process that leads to AKT promoting cell growth

A
  1. AKT phosphorylate Bad
  2. This release Bcl2 from Bad
  3. Bcl2 leads to cell survival by inhibition of apoptosis

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