Cell Signalling 2 Flashcards

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1
Q

What causes a secondary messenger to be released when a molecule binds to a receptor?

A

The protein binds to a G-protein coupled receptor and causes a conformational change situating the secondary messengers.

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2
Q

What are the 4 types of receptors?

A

G protein coupled receptors (single chain of amino acids), intrinsic receptors (2 come together to form a dimer), ion channel receptors and DNA binding receptors (a dimer)

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3
Q

Briefly describe the process when a ligand binds to a receptor

A

The ligand binds to a receptor and a conformational change occurs, exposing the G - protein. The G - protein bind to the receptors once the agonist has bound. Exchange of GDP for GTP on the G - protein. Secondary messengers are released.

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4
Q

What are the 7 cellular location of receptors?

A

1) Nuclear receptors = interact with DNA aiding transcription and translation
2) Intracellular receptors
3) Plasma membrane receptors e.g. ligand gated ion channels, G-protein coupled receptor
4) Intrinsic enzyme receptor (tyrosine kinase receptor)
5) Ion channel receptors (allow ions to enter the cell once a chemical messenger is present)
6) DNA binding receptors

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5
Q

What is the insulin receptor an example of?

A

A tyrosine kinase receptor (intrinsic enzyme receptor)

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6
Q

What are the three parts of an insulin receptor? What is the form of the insulin receptor?

A

Ligand binding, transmembrane, enzyme.

It is a dimeric form as two monomers are joined up by disulphide bonds.

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7
Q

How does an intrinsic enzyme receptor work?

A

Ligand joins to the ligand binding site, two monomers come together to form a dimer. Autophosphorylation and substrate phosphorylation occurs leading to conformational changes.

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8
Q

What are 3 things that RTK (receptor tyrosine kinase) does?

A
  • causes phosphorylation = phosphorylated tyrosine bind to kinase and signalling proteins bind to this
  • activates RAS (G - protein) = signal molecule binds and G - protein is activated. Exchange of GDP for GTP activating it.
  • activates MAP kinase signalling = G - protein from RTK activated kinase. Phosphorylation of transcription factor which activates it,
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9
Q

Outline the steps in the action of receptor tyrosine kinase signalling.

A
  1. Ligands binds to receptor
  2. Conformational change for receptor results in autophosphorylation at tyrosine residues
  3. Recruitment of RAS (G-protein)
  4. Exchange of GDP for GTP on RAS results in a conformational change
  5. Activation of MAP kinase by phosphorylation
  6. Further protein phosphorylation in cell signalling
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10
Q

What are the forms that receptors can come in?

A

Pentameric, tetrameric, trimeric

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11
Q

How does the ion-channel coupled receptors work?

A

Signal molecule binds and this causes a conformational change to make the channel hydrophilic and ions can therefore pass through.

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12
Q

What type of receptor is an acetylcholine receptor? How does it work?

A

It is a ligand gated ion channel receptor. When closed, hydrophobic amino acids side chains keep pore closed. Acetylcholine binds to receptor leading to a conformational change. The gate opens and ions enter

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13
Q

What is the structure of a DNA binding receptor?

A

Ligand binding at top, zinc fingers in middle, co-activator region at bottom

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14
Q

How does a DNA binding receptor work?

A

Ligand floating in the cytoplasm where the receptors are. It binds to the receptor and recruits another receptor to become a dimer. The dimer goes into the nucleus and binds to the promoters in the DNA causing a conformational change in the DNA leading to transcription.

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15
Q

What do glucocorticoids do?

A

Anti-inflammatory as they inhibit transcription of cytokines interleukins.

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16
Q

Compare the structure and speed of all the receptor types

A

Ion channel - multiple subunits, very fast
GPCR - Single protein, fast
Intrinsic enzyme - dimer, slow
DNA binding - dimer, very slow