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BVM&S > CB17: Receptors > Flashcards

CB17: Receptors Flashcards

1
Q

Define ligand.

A

A small molecule that binds to a specific receptor and initiates a response.

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2
Q

Define receptor.

A

A macromolecule that recognises a specific ligand and without the ligand, is silent.

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3
Q

What is juxtacrine signalling?

A

A signal transmitted for cells that are next to each other. Signal still touches the cell that secreted it.

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4
Q

What is autocrine signalling?

A

Signal is transmitted from one cell to itself.

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5
Q

What is endocrine signalling?

A

Signal is transmitted via blood.

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6
Q

What is paracrine signalling?

A

The signal is transmitted between cells that are next to each other but not touching.

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7
Q

How does the distance for the 4 types of signalling compare?

A
  • Autocrine: short distance
  • Juxtacrine: short distance
  • Paracrine: µm-mm
  • Endocrine: cm-m
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8
Q

What is a sub-type of paracrine signalling and what is the distance & response type for it?

A

Synaptic signalling.
Distance: 50nm
Response time: <1milisec

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9
Q

How does the response time for the 4 types of signalling compare?

A
  • Autocrine: short
  • Juxtacrine: short
  • Paracrine: <1sec
  • Endocrine: sec-min
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10
Q

Why are receptors located at the cell surface?

A

Most ligands can’t cross the plasma membrane due to being too pig, polar or charged.

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11
Q

What are the 3 main categories of receptors?

A
  • Ligand-gated ion channels,
  • Enzyme-linked receptors,
  • G-protein coupled receptors.
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12
Q

What kinds of molecules can have intracellular receptors?

A

Small, non-polar & uncharged molecules, like steroid hormones.

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13
Q

Define Kd.

A

The ligand concentration at which half of the receptors are bound.

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14
Q

What does Kd show ?

A

It shows a ligand’s affinity for a receptor.

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15
Q

If Kd is low what does this mean?

A

The ligand’s affinity for the receptor is high.

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16
Q

If Kd is high what does this mean?

A

The ligand’s affinity for the receptor is low.

17
Q

What are the axis for the ligand-receptor binding curve?

A
  • Y-axis: bound radiolabel
  • X-axis: [ligand]
18
Q

Define EC50.

A

The ligand concentration that produces half of the maximal response.

19
Q

What does EC50 show?

A

A ligand’s potency.

20
Q

If EC50 is low what does this mean?

A

The ligand is very potent.

21
Q

If EC50 is high what does this mean?

A

The ligand is not very potent.

22
Q

What are the axis for the dose-response curve?

A
  • Y-axis: response
  • X-axis: [ligand]
23
Q

What are the units for Kd & EC50?

A

Units of concentration.

24
Q

Define agonist.

A

A molecule whose binding activates the receptor & produces a response (the same as the one produced by the natural ligand).

25
Q

Define antagonist.

A

A molecule whose binding does not activate the receptor or produce a response, but whose binding interferes with the natural binding of the ligand.

26
Q

Differentiate between affinity and efficacy.

A

Affinity is the tendency of a ligand to bind to the receptor while efficacy is the ability of a ligand to produce a response.

27
Q

What is a full agonist?

A

An agonist that will be able to achieve the maximal response.

28
Q

What is a partial agonist?

A

An agonist that will not be able to achieve the maximal response.

29
Q

What is a competitive antagonist?

A

An antagonist that binds to the same binding site as the ligand.

30
Q

What is an irreversible competitive antagonist?

A

An antagonist that binds to the same binding site as the ligand but never leaves the binding site.

31
Q

What is a non-competitive antagonist?

A

An antagonist that does not bind to the same binding site as the ligand.

32
Q

State how the different antagonists can be overcome.

A
  • Competitive antagonist: overcome by increasing [ligand].
  • Irreversible competitive antagonist: not overcome.
  • Non-competitive antagonist: not overcome by increasing [ligand].
33
Q

Can maximal response be achieved with the different antagonists?

A
  • Competitive antagonist: yes
  • Irreversible competitive antagonist: no
  • Non-competitive antagonist: no
34
Q

How does the log[dose]-response curve look like with the different antagonists?

A
  • Competitive antagonist: shape & size is same, curve is shifted right.
  • Irreversible competitive antagonist: curve is shifted right & smaller.
  • Non-competitive antagonist: curve is shifted right + shape changes.
35
Q

How is maximal response achieved despite not all receptors being bound?

A

Due to a cell’s spare receptors.

36
Q

What is up-regulation?

A

Increasing sensitivity to the ligand by increasing the number of receptors.

37
Q

What is down-regulation?

A

Decreasing sensitivity to the ligand by decreasing the number of receptors.

BVM&S (10 decks)

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