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Cells to systems > Lecture 22 > Flashcards

Lecture 22 Flashcards

cell communication

1
Q

What are the steps for signal transduction

A
  1. Reception
  2. Transduction
  3. Response
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2
Q

What is signal transduction

A

How a signal molecular cause a cellular response

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3
Q

what happen after a signal molecule activate the signal rec

A

The signal receptor switched on by a conformational change(primary transduction

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4
Q

What happens after the signal receptor is switched on

A

It will relay to a second messenger (enzymes) and start the amplification. Which then start diverting to multiple targets to cause a response.

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5
Q

What are the types of receptors

A
  1. ligand-gated ion channels (ionotropic receptors)
  2. G-protein-coupled receptor (metatropic)
  3. Kinase-linked receptors
  4. Nuclear receptors
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6
Q

What is the signal transduction pathway for ligand-gated ion channels (ionotropic receptors)

A

Ions from the extracellular will enter cell after a ligand if attached and cause a hyperpolarisation or depolarisation.

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7
Q

How fast does ligand-gated ion channels (ionotropic receptors) act

A

Milliseconds, e.g. Nicotinic, ACh receptor

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8
Q

Does ligand-gated ion channels (ionotropic receptors) have transduction

A

No, the mechanism is ion current

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9
Q

What does the G-protein-coupled receptor (metatropic) signal the cell

A

The ion channels and enzyme will open when a protein is attached to the coupled G-protein receptor. Enzyme will send a signal to the second messenger which cause cellular effects using, Ca2+ release, protein phosphorylation and others. While ion change in excitability of the cell effects

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10
Q

How fast a G-protein-coupled receptor (metatropic) act

A

seconds

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11
Q

what is the Kinase-linked receptors transduction pathway

A

Receptor or enzyme will receive the signal molecule which start the process of Protein phosphorylation > gene transcription > protein synthesis > cellular effects

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12
Q

what second messager are used in G-protein-coupled receptor (metatropic)

A

Second messenger
cAMP, cGMP, DAG, IP3
and Ca++

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13
Q

What is the time scale for Kinase-linked receptors transduction

A

hours

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14
Q

What are examples of Kinase-linked receptors transduction

A

cytokine receptor

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15
Q

What is Kinase-linked receptors

A

Receptor is an
enzyme or part
of enzyme
complex

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16
Q

what is the pathway of nuclear receptor

A

Signal molecule will enter the cell and attached the receptor which is a cytosolic or nuclear which then promote gene transcription >protein synthesis > cellular effects

17
Q

What is the time scale for Kinase-linked receptors

A

hours

18
Q

What are examples of nuclear receptor

A

oestrogen receptor

19
Q

What receptor is Acetylcholine (ACh)

A

• Ionotropic receptor
Nicotinic Ach receptor
Opens Na+ ion channel
Depolarizati

20
Q

What Does G protein mean

A 
G proteins (guanine
nucleotide-binding proteins,

Coupled to intracellular
effector systems via Gprot

21
Q

What the steps for GPCRs

A
  1. Binding of hormone induces a conformational change in receptor
  2. activated receptor binds to Ga subunit
  3. Binding induces conformational change in Ga ; bound GDP dissociates and replaced by GTP; Ga dissociates from Gby
  4. Hormone dissociates from receptor; Ga binds to effector activating it.
  5. hydrolysis of GTP to GDP causes Ga to dissociate from effector and reassociate with Gby
22
Q

What are the steps for Adrenaline/adrenergic receptor

A 
1. G protein a subunit
with GTP activates
adenylyl cyclase
2. Adenylyl cyclase
hydrolyses ATP to
cAMP
3. cAMP binds to PKA
regulatory subunit
and releases the
PKA catalytic unit
4. Catalytic unit is
phosphorylated
5. Activated PKA
phosphorylates
glycogen
phosphorylase
enzyme
6. Glycogen broken
down to glucose
23
Q

What is the use of

• Proteins called b-arrest

A

• Proteins called b-arrestins bind to GPCR and downregulate a
response to prolonged hormone exposure (desensitization)
Inactivate GPCR
Promote removal by endocyt

24
Q

What does Phosphodiesterase enzyme do

A

breaks down cAMP (regulatory control)

25
Q

What do kinases do??

A

Reversible phosphorylation

26
Q

What do cholera toxin do

A

Cholera toxin inhibits
G protein hydrolysis
-Switched on longer

27
Q

What is one benefit of a G protein

A

It is amplification

28
Q

What does caffeine do

A

It is a PDE enzyme inhibitor, theophylline where is inhibits phosphodiesterase from converting cAMP to 5’ AMP, thus maintaining cAMP at a high level.

29
Q

Where does the phosphorus bind to in ATP kinase

A

tyrosine,
threonine or
serine residue

30
Q

What does cholera toxin do to the cell

A

preventing switching off of the adenlylate cyclase

31
Q

what is the effect of cholera toxin

A

The toxin a subunit detaches and catalyses
ADP ribosylation (addition of a ribosome unit)
of the Gas protein coupled to adenylyl cyclase
• Inhibits GTPase activity and GTP cannot be
hydrolysed back to GDP

The toxin a subunit detaches and catalyses
ADP ribosylation (addition of a ribosome unit)
of the Gas protein coupled to adenylyl cyclase
• Inhibits GTPase activity and GTP cannot be
hydrolysed back to GDP

Cells to systems (25 decks)

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