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IMS > PHARMACOLOGY 1 > Flashcards

PHARMACOLOGY 1 Flashcards

1
Q

what is a type 1 receptor?

A

fast neurotransmission - directly coupled to an ion channel – ionotropic receptors

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2
Q

what is a type 2 receptor?

A

signal via G-protein pathways – metabotropic receptors

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3
Q

what is a type 3 receptor?

A

signal via enzyme-linked cell surface receptors

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4
Q

what is a type 4 receptor?

A

located in specialized regions of DNA, activation directly promotes gene up-regulation

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5
Q

what does the nicotinic Ach receptor consist of?

A

5 memb spanning subunits - 2 alpha, beta, gamma, delta

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6
Q

how does the nicotinic Ach receptor open?

A

2 Ach molecules bind to the 2 units - this opens the ligand-gated Na ion channel and depolarises the cell.

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7
Q

what is intracellular signalling?

A

describes the way the binding of a ligand with a receptor activates an enzyme cascade, ultimately inducing a cellular response.

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8
Q

what is the function of receptors?

A

provide a means of selectively transmitting extracellular signals across the cell membrane, enabling cells to respond to the stimuli.

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9
Q

what do cellular responses include?

A

opening of ion channels, increased secretion of other signalling molecules, cell motility and modifications of the cell cycle

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10
Q

what are the 2 types of intracellular signalling?

A

G-protein pathway - Type 2 receptors

enzyme-linked cell surface receptor pathway - Type 3 receptors

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11
Q

what do type 2 receptors consist of?

A

most consist of a single polypeptide chain forming seven transmembrane helices arranged with an extracellular N-terminus and a cytoplasmic carboxy terminus

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12
Q

where does the ligand bind in type 2 receptors?

A

binds to a binding site in the helices embedded in the memb

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13
Q

what part of the receptor couples to a G-protein?

A

the 3rd loop

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14
Q

what are G-proteins?

A

Exist as highly mobile proteins in the membrane

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15
Q

what do G-proteins consist of?

A

consist of 3 subunits, alpha, beta and gamma

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16
Q

what does the alpha subunit function as?

A

as a GTPase, converting GTP to GDP

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17
Q

what do the beta and gamma subunits do?

A

and  subunits form a complex, are very hydrophobic and stay closely associated with the memb

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18
Q

what happens when the protein is inactivated?

A

the alpha, beta and gamma subunits form a complex in which GDP is bound to an alpha subunit

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19
Q

what is the 1st stage of G protein activation?

A

Binding of a ligand to the receptor - allows a conformational change in the alpha, beta and gamma complex, allowing the alpha to exchange the GDP for a GTP and this causes the alpha to dissociate from the beta and gamma and subunits.

20
Q

what is the 2nd stage of G protein activation?

A

The  coupled to the GTP then associates with specific allosteric target enzyme such as an adenylate cyclase.

21
Q

what is the 3rd stage of G protein activation?

A

The  hydrolyses GTP into GDP. This inactivates the enzymatic ability of the  alpha subunit whilst allowing the activation of the target enzyme. The inactive alpha subunit then re-associates with the beta and gamma complex

22
Q

what can the G protein mechanism act as?

A

as a signal amplifier - a single activated receptor can activate several G proteins.

23
Q

what are the targets for G proteins?

A

Adenylate cyclase
Guanylate cyclase
Phospholipase C/inositol phosphate system
The regulators of ion channels

24
Q

what does adenyl cyclase produce?

A

intracellular cAMP

25
Q

what does guanyl cyclase produce?

A

intracellular cGMP

26
Q

what does activated adenyl cyclase do?

A

converts ATP into cAMP

27
Q

what is cAMP?

A

cyclic 3’,5’-adenosine monophosphate, cAMP functions as a secondary messenger and is inactivated by hydrolysis into 5’-AMP.

28
Q

how does cAMP act?

A

targets inactive protein kinases, activating them

29
Q

what do the activated protein kinases do?

A

use ATP as a source of phosphate groups and phosphorylate downstream enzymes thus activating them.

30
Q

give an example of cAMP’s role

A

cAMP role in beta adrenoceptor activated breakdown of glycogen

31
Q

how is cAMP inactivated?

A

by phosphodiesterase. Inactivation can be inhibited by drugs such as caffeine.

32
Q

what is the phosphoinositide system?

A

based on memb phospholipid phosphoinositide (4,5) diphosphate (PIP2)

33
Q

what is the role of PIP2?

A

acts as a substrate for a membrane-bound enzyme phospholipase C (PLC) which spits PIP2 into diacylglycerol (DAG) and inositol (1,4,5) triphosphate InsP3.

34
Q

what are the secondary messengers in the phosphoinositide system?

A

DAG and InsP3

35
Q

what do DAG and InsP3 do?

A

DAG results in protein kinase C activation and InsP3 promotes Ca2+ release from intracellular stores

36
Q

how does InsP3 work?

A

binds to endoplasmic receptors and opens endoplasmic Ca2+ channels. This allows the release of Ca2+ into the cytosol where the Ca2+ can interact with a whole range of targets

37
Q

what is Ca important in?

A

Muscle contraction
Control of secretion from exocrine glands (ie., the muscarinic ACh receptor)
Hormone release

38
Q

what does DAG activate?

A

activates PKC which is a serine/threonine kinase and acts by phosphorylating downstream target enzymes.

39
Q

what things are associated with the PKC being activated?

A

Muscle contraction
Inflammatory response
Increased neurotransmitter release

40
Q

what effect do G-proteins have on ion channels?

A

directly activate ion channels, ie., interaction of ACh and muscarinic receptors opens potassium channels via a G-protein pathway

41
Q

how does the guanyl cyclase receptor work?

A

Extracellular domain binds the ligand.

On binding ligand, intracellular domain (the guanylyl cyclase) becomes activated and produces cyclic GMP.

42
Q

what does cyclic GMP do?

A

binds to cyclic GMP-dependent protein kinase (G-kinase)

43
Q

what does G-kinase do?

A

phosphorylates downstream proteins on either threonine or serine residues

44
Q

what is the secondary messenger in the guanyl cyclase receptor system?

A

cyclic GMP

45
Q

give an example of guanylyl cyclase receptor

A

the receptor for atrial natriuretic peptide.

46
Q

what are type 3 receptors?

A

Trans-Memb proteins possessing an extracellular ligand binding domain and a cytoplasmic domains that have an intrinsic enzymatic activity.

47
Q

what are the 4 kinds of type 3 receptors?

A

tyrosine kinases
Receptor linked tyrosine kinases
tyrosine phosphatases
serine/threonine kinases

IMS (52 decks)

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