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Cells > Cell Signalling > Flashcards

Cell Signalling Flashcards

1
Q

What are the 6 steps to cell communication?

A 
Synthesis of signal
Release of signal 
Transport of signal 
Detection of signal
Change in the cellular process
Removal of signal
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2
Q

What are the different types of cell signaling?

A 
Direct contact
Paracrine signaling 
Autocrine signaling
Endocrine signaling
Synaptic signaling
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3
Q

What is direct contact signaling?

A

Transferring a signal molecule across a gap junction between neighboring cells

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4
Q

What is paracrine signaling?

A

A cell produces a signal to induce changes in nearby cells

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5
Q

What is autocrine signalling?

A

A cell produces a signal that induces a change on the same cell

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6
Q

What is endocrine signaling?

A

A cell produces a signaling molecule which travels through the bloodstream to bind to receptors on a distant cell

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7
Q

What is synaptic signalling?

A

A cell produces a signal to induce a change in nearby cells, passing the signal through a synapse

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8
Q

What occurs in a cell after a signal arrives?

A

The ligand binds to the receptor, inducing a single response or multiple responses

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9
Q

What is phosphorylation?

A

The addition of a phosphate to an organic compound

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10
Q

What is a protein kinase?

A

An enzyme that phosphorylates proteins

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11
Q

How does a protein kinase carry out its function?

A

It removes a phosphate from ATP and then gives that phosphate to a protein

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12
Q

What is a protein phosphatase?

A

An enzyme that dephosphorylates a protein

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13
Q

What are the different types of cell surface receptors?

A

Chemically gated ion channels
Enzymatic receptors
G-protein coupled receptors

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14
Q

How does a chemically gated ion channel work?

A

A ligand binds to the channel, opening it. This allows the movement and transport of ions through the channel

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15
Q

How do enzymatic receptors work?

A

The binding of an extracellular ligand cause intracellular enzymatic activity

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16
Q

How do G-protein coupled receptors work?

A

A ligand binds to the receptor which stimulates the conversion GDP to GTP which activates an enzyme or ion channel

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17
Q

How are intracellular receptors reached?

A

A ligand must be able pass through the cell membrane to reach these
Then ligand can then bind to recpetor in the cytoplasm or nucleus

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18
Q

Why can a steriod activate intracellular receptors?

A

As steriods are lipid soluble meaning they can pass through the membrane into the cell

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19
Q

What are steriod receptors and what do they do?

A

Steriod receptors are intracellular receptors that initiate signal transduction for steroid hormones which changes gene expression

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20
Q

What are the binding domains of a steroid receptor?

A

Hormone-binding domain

DNA binding domain

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21
Q

What occurs at the hormone-binding domain of steroid receptors?

A

Forms a hormone receptor complex

Initiates signal transduction which leads to a change in gene expression

22
Q

What occurs at the DNA binding domain of steroid receptors?

A

Once the steriod hormone binds to the receptor, the receptor dimerises and binds to the DNA sequence
-acts as a transcription factor

23
Q

What are receptor tyrosine kinases (RTK)?

A

High affinity cell receptors involved in regulating lots of normal cell processes such as the cell cycle, growth, proliferation, metabolism etc

24
Q

How are receptor tyrosine kinases regulated?

A

By autophosphorylation
When a ligand binds to the receptor is induces the dimerization of the 2 receptors allowing them to phosphorylate themselves

25
Q

What is the insulin receptor?

A

A receptor that insulin binds to when blood glucose is high

26
Q

Where is insulin made and what does it do?

A

Insulin is made in the pancreas

Insulin stimulates the formation of glycogen from glucose

27
Q

What is a glucose transporter?

A

A membarne protein that facilltates the movement of gluocse across the cell membrane

28
Q

What occurs when insulin binds to the insulin receptor?

A
  • Glucose transporters stored in membrane vesicles
  • When insulin binds to the insulin receptor, glucose transporters move to the cell membrane for movement of glucose ( decreasing blood glucose)
  • When insulin levels decrease glucose transporters move back into membrane vesicles
29
Q

What are docking proteins?

A

Proteins that dock onto and help other proteins dock onto phosphotyrosines to become phosphorylated

30
Q

What happens at the glycogen synthase signaling pathway?

A
  • Insulin binds to extracellular domain of receptor
  • Causes the autophosphorylation of the intracellular domain
  • Insulin response protein (docking protein) binds
  • Activates glycogen synthase which converts glucose to glycogen (blood sugar decreases)
31
Q

What is a kinase cascade?

A

Where a protein kinases phosphorylates another proetins kinases and that repeates until MAP kinase activated

32
Q

What is MAP kinase stand for?

A

Mitogen-activated protein kinase

33
Q

How could amplification of the kinase cascade or signal occur?

A

If each enzyme acts on multiple substrates

Therefore large amount of final product, meaning a larger response

34
Q

What are scaffold proteins?

A

A large protein that groups together and organises the kinase cascade for ultimate efficiency

35
Q

What are G-proteins and what do they do?

A

Family of proteins that act as molecular switches inside cells
-They are heterotrimeric membrane associated proetins that bind GTP
They link the receptor proteins to the effector proteins

36
Q

What is adrenaline and where is it made?

A

Made in the adrenal glands

Mediates stress response- mobilisation of energy

37
Q

Which cells can adrenaline bind to?

A

Liver cells
Adipose cells
Heart cells

38
Q

What does adrenaline induce when it binds to recpetors in liver cells?

A

The breakdown of glycogen

39
Q

What does adrenaline induce when it binds to recpetors in adipose cells?

A

Lipid hydroysis

40
Q

What does adrenaline induce when it binds to recpetors in heart cells?

A

Increased heart rate

41
Q

Explain the process that occurs when adrenaline binds to its receptor?

A
  • Adrenaline binds to the G-protein coupled receptor
  • Beta and Gamma subunits dissociate from the G-protein
  • Allows for conversion of GDP to GTP
  • GTP and alpha subunit activate adenylyl cyclase
  • Adenylyl cyclase converts ATP into cAMP
  • This activates PKA, which activates response proteins to create a cellular response
42
Q

Explain the self-inactivation of G-protein signaling?

A
  • When G-proteins bound with GDP they are off
  • Displacement if GDP by GTP turns it on
  • Beta and Gamma subunits dissociate allowing the GTP and alpha to activate adenylyl cyclase
  • Once activating adenylyl cyclase it gets dephosphorylated back to GDP
  • Allowing beta and gamma subunits to redissociate (turning it off)
43
Q

What are Beta-adrenergic receptors?

A

They are a class of G-protein coupled receptors

44
Q

What does BARK stand for?

A

Beta-adrenergic protein kinase

45
Q

What does Barr stand for?

A

Beta-arrestin

46
Q

Explain the desensitization of Beta-adrenergic receptors?

A
  • Binding of Epinephrine to Beta-adrenergic receptor triggers dissociation of the beta and gamma subunits of the g protein
  • The beta and gamma subunits recruit BARK which phosphorylates the carboxyl terminus of receptor
  • Barr binds to the now phosphorylated terminus of the receptor
  • Receptor-arrestin complex moves into cell by endocytosis (removing from cell membrane) then Barr dissociates
47
Q

Explain and example of how G-protein coupled receptors can use other secondary messenger molecules (activating PLC)?

A
  • GTP bound alpha subunit of G protein activates phospholipase C (PLC)
  • PLC cleaves PIP2 into IP3 and DAG
  • IP3 moves into endoplasmic reticulum, causing calcium ions to move out and activate calcium sensing protiens such as PKC or calmodulin
  • DAG also activates PKC (protein kinase C)
48
Q

Explain how different G proteins can activate the same tranduction pathway in a flight or flight response?

A
  • Adrenaline and Glucagon
  • Both initiates the conversion of GDP to GTP, and then ATP to cAMP
  • Collectively activating PKA
  • Activating phosphorylase kinase
  • Activating glycogen phosphorylase which converts glycogen to glucose for mobilization of energy
49
Q

Give an example of how adrenaline can have different effects on things ?

A

-Increases the heart rate
- But relaxes the smooth muscle of intestine
(less peristalsis- as we are not interested in digesting food at this point)

50
Q

Explain how different G proteins have an opposite effect on the same transduction pathway?

A
  • A stimulatory hormone such as epinephrine makes a stimulatory G protein complex to activate adenylyl cyclase- production of cAMP
  • But an inhibitory protein such as adenosine makes an inhibitory G protein complex which deactivates adenylyl cyclase- no production of cAMP
51
Q

What is meant by the intergation of signals?

A

When 2 signals have opposite effects on metabolic characterist
-so the overall effect and strength is based on the concentration of each one (which one cancels out)

52
Q

What is the specificity of a signal molecule?

A

That a signal molecule fits to binding site on complementary receptor - other signals don’t fit

Cells (8 decks)

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