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Cell Signalling Flashcards

(52 cards)

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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?

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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?

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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)?

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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?

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A

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

25
What is the insulin receptor?
A receptor that insulin binds to when blood glucose is high
26
Where is insulin made and what does it do?
Insulin is made in the pancreas | Insulin stimulates the formation of glycogen from glucose
27
What is a glucose transporter?
A membarne protein that facilltates the movement of gluocse across the cell membrane
28
What occurs when insulin binds to the insulin receptor?
- 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
What are docking proteins?
Proteins that dock onto and help other proteins dock onto phosphotyrosines to become phosphorylated
30
What happens at the glycogen synthase signaling pathway?
- 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
What is a kinase cascade?
Where a protein kinases phosphorylates another proetins kinases and that repeates until MAP kinase activated
32
What is MAP kinase stand for?
Mitogen-activated protein kinase
33
How could amplification of the kinase cascade or signal occur?
If each enzyme acts on multiple substrates | Therefore large amount of final product, meaning a larger response
34
What are scaffold proteins?
A large protein that groups together and organises the kinase cascade for ultimate efficiency
35
What are G-proteins and what do they do?
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
What is adrenaline and where is it made?
Made in the adrenal glands | Mediates stress response- mobilisation of energy
37
Which cells can adrenaline bind to?
Liver cells Adipose cells Heart cells
38
What does adrenaline induce when it binds to recpetors in liver cells?
The breakdown of glycogen
39
What does adrenaline induce when it binds to recpetors in adipose cells?
Lipid hydroysis
40
What does adrenaline induce when it binds to recpetors in heart cells?
Increased heart rate
41
Explain the process that occurs when adrenaline binds to its receptor?
- 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
Explain the self-inactivation of G-protein signaling?
- 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
What are Beta-adrenergic receptors?
They are a class of G-protein coupled receptors
44
What does BARK stand for?
Beta-adrenergic protein kinase
45
What does Barr stand for?
Beta-arrestin
46
Explain the desensitization of Beta-adrenergic receptors?
- 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
Explain and example of how G-protein coupled receptors can use other secondary messenger molecules (activating PLC)?
- 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
Explain how different G proteins can activate the same tranduction pathway in a flight or flight response?
- 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
Give an example of how adrenaline can have different effects on things ?
-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
Explain how different G proteins have an opposite effect on the same transduction pathway?
- 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
What is meant by the intergation of signals?
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
What is the specificity of a signal molecule?
That a signal molecule fits to binding site on complementary receptor - other signals don't fit

Cells (8 decks)

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