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ICPP * > S6 - Receptors > Flashcards

S6 - Receptors Flashcards

1
Q

What is paracrine signalling?

A

Secreted molecules (local mediators) acting on local cells/tissues

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2
Q

What is endocrine signalling?

A

Secreted molecules (hormones) acting on distant cells/tissues (travel through blood stream)

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3
Q

What is synaptic signalling?

A

Secreted molecules (neurotransmitters) acting across a synapse in the nervous system

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4
Q

What are the two types of intercellular signalling?

A
  1. Signalling by secreted molecules

2. Signalling by plasma membrane bound molecules

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5
Q

Where can you find receptors in a cell?

A
  1. On the cell surface

2. Inside the cell (intracellular)

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6
Q

What is a receptor?

A

A molecule that recognises specifically a second molecule (ligand)/family of molecules and binding of the ligand results in regulation of cellular processes.

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7
Q

What is a receptor in the unbound state described as?

A

Functionally silent

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8
Q

What is a ligand?

A

A molecule that binds specifically to a receptor site - agonist or antagonist

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9
Q

What is an agonist?

What is an antagonist?

A

Agonist - activates receptor/channel

Antagonist - prevents activation of receptor/block channel

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10
Q

Give some roles of receptors in cells.

A
  1. Neurotransmission
  2. Control of gene expression
  3. Cell adhesion
  4. Regulation of immune responses
  5. Release of intracellular calcium and proteins
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11
Q

Which has a higher affinity, ligand to receptor or substrate to enzyme?

A

Ligand to receptor

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12
Q

What are the two ACh receptor types?

A

Nicotinic and muscarinic (M1, M2, M3)

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13
Q

What are the four ways of signal transduction?

A
  1. Membrane-bound receptors with integral ion channels
  2. Membrane-bound receptors with integral enzyme activity
  3. Membrane-bound receptors which couple to effectors through transducing proteins
  4. Intracellular receptors
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14
Q

How many subunits make up a ACh receptor?

A

5

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15
Q

Describe the structure of membrane-bound receptors with integral enzyme activity?

A

A binding domain outside the cell and a catalytic domain inside the cell

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16
Q

How does a tyrosine kinase-linked receptor work?

A

The tyrosine chains autophosphorylate which leads to phosphorylation of other biological molecules e.g. enzymes to activate it

Or leads to the phosphorylation of a transducer which phosphorylates a biological molecule e.g. enzyme to activate it

17
Q

What type of receptor is an insulin receptor? And what is its structure?

A

Tyrosine kinase-linked receptor

In the extracellular space (N-terminal) there is an insulin binding domain with alpha and beta subunits (2 of each), there is a transmembrane domain and a tyrosine kinase domain in the cytoplasm (C-terminal)

18
Q

How many transmembrane domains does a GPCR have?

A

7

19
Q

What does adrenaline binding to beta-adrenoceptors activate?

A

Activates enzyme adenylyl cyclase (ATP —> cAMP) via an alpha-s G-protein

20
Q

What does ACh binding to M2 mAChRs stimulate?

A

Stimulates K+ channel opening via an alpha-i G-protein

21
Q

Where are the binding domains in GPCRs?

A

Outside the cell/near the N terminus and in between the transmembrane subunits

22
Q

What is bound to the G-protein coupling domain?

A

3 subunits - beta, gamma and alpha subunits

Alpha has GDP bound and the beta and gamma remain bound

23
Q

QISS QIQ(IQ)

A

Q - alpha 1
I - alpha 2
S - beta 1
S - beta 2

Q - M1
I - M2
Q - M3
(I) - (M4)
(Q) - (M5)
24
Q

Describe the general reaction that happens when a ligand binds to a GPCR and how the reaction stops.

A
  1. Ligand binding activates the receptor
  2. G-protein subunit dissociation - gamma + beta and alpha + GDP
  3. Alpha subunit undergoes GDP for GTP exchange
  4. This causes activation of biological molecules
  5. GTPase converts GTP to GDP stopping activation of the biological molecules
  6. Re-association of subunits at receptor
25
Q

What are intracellular receptors?

A

Receptors within cell

26
Q

What are two examples of a intracellular receptors and their functions?

A
  1. Nuclear receptors - activate/inhibit transcription

2. IP3 receptors (ryanodine receptors) - release Ca2+ from SER

27
Q

Give some examples of nuclear receptors.

A
  1. Cortisol receptor
  2. Oestrogen receptor
  3. Progesterone receptor
  4. Vitamin D receptor
  5. Thyroid hormone receptor
28
Q

What is the structure of a nuclear receptor?

A

Binding domain at the C-terminus and a DNA-binding domain in the middle/closer to the N-terminus

29
Q

What are the effects of noradrenaline and ACh on cardiac pacemaker cells?

A

Noradrenaline - acts on beta-1 adrenoceptors - increase heart rate

ACh - act on M2 muscarinic receptors - decreases heart rate

30
Q

What are the effects of insulin and glucagon on hepatocytes?

A

Insulin - stimulates glycogen synthesis from glucose

Glucagon - stimulates glycogen breakdown to glucose

ICPP * (10 decks)

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