7 Receptor and Effector Mechanisms Flashcards

0
Q

Describe a receptor with intrinsic enzymatic activity

A

Ligand binding activates enzyme activity that phosphorylates the receptor itself and other substrates.

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1
Q

Define a ligand-gated ion channel

A

The intrinsic pore of a receptor opens when a complementary ligand binds to the receptor.

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2
Q

Give examples of ligands GPCRs respond to

A

Ions
Neurotransmitters
Hormones
Large glycoproteins

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3
Q

Describe the common basic structure of a GPCR

A

Single polypeptide chain
7 transmembrane spanning regions
Extracellular N terminal
Intracellular C terminal

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4
Q

Where can a ligand bind to a GPCR?

A

Between the 2nd and 3rd transmembrane domain

The N-terminal region

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5
Q

What is a G-protein made up of?

A

3 subunits, alpha, beta, gamma

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6
Q

How does a G-protein work?

A

When a ligand binds to the GPCR:
GTP => GDP
The ‘a-By’ complex then dissociates.
Each G subunit interacts with effector proteins
GDP => GTP (via GTPase)
‘By’ then regains affinity for ‘a’ to reform the G-protein complex

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7
Q

What is the result of Ga and GBy subunits being specific to effector proteins?

A

1 type of GPCR will activate 1 type of G-protein and therefore 1 effector to produce a response.

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8
Q

Describe the actions of adenyl cyclase

A

ATP => cyclic AMP

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9
Q

How does cyclic AMP cause a cellular response?

A

cAMP binds to the regulatory area of AMP-dependent protein kinase (PKA). The catalytic area then detaches to create an effect.

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10
Q

How does Phospholipase work in the cell? What is the final response?

A

PIP2 => IP3 + DAG

Ca2+ released from intracellular stores

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11
Q

How does adrenaline and noradrenaline increase inotropy?

A

Interact with ventricular B1-adrenoceptors

PKA phosphorylates VOCC so more Ca2+ enters the cell on depolarisation. This increases the contraction of the heart.

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12
Q

How is neurotransmitter release modulated by GPCRs?

A

The GBy subunit inhibits some VOCCs, reducing Ca2+ influx and neurotransmitter release.

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