Signalling Transfuction 1

Question 1

Examples of extracellular signalling molecules

Answer 1

Hormones
Neurotransmitters
Growth factors

Question 2

For what molecules are receptors intracellular

Answer 2

Steroid
Thyroid hormones

Question 3

3 superfamilies of cell-surface receptor

Answer 3

G protein-couples (7TM) receptors
Ligand-gated (receptor-operated) ion channels
Receptors with intrinsic enzymatic activity

Question 4

What follows ligand binding

Answer 4

Activation of receptor

Question 5

Example of G protein-coupled (7TM) receptors

Answer 5

Muscarinic acetylcholine receptors

Question 6

Example of ligand-gated ion channels

Answer 6

Nicotine acetylcholine receptors

Question 7

Example of intrinsic enzymatic activity

Answer 7

Receptor with tyrosine kinases
E.g.) insulin receptor

Question 8

Difference between agonist and antagonist

Answer 8

Agonist: bind to the receptor and activate it
Antagonist: bind to the receptor, but do NOT activate it

Question 9

Basic structure of GPCRs

Answer 9

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

Question 10

Where are the two regions of GPCRs responsible for ligand binding

Answer 10

Transmembrane
N-terminal region

Question 11

How do GPCRs reposed to ligands

Answer 11

Conformational change
(Change their 3D shape)

Question 12

G protein stands for

Answer 12

Guanine nucleotide-binding protein

Question 13

What are the three subunits of G proteins

Answer 13

Alpha
Beta
Gamma

Question 14

How do GPCRRs cause a change in cellular activity

Answer 14

GPCR-G protein interaction activates G protein by causing GTP to exchange to GDP on the G protein alpha subunit

Question 15

Describe the sequence of G-protein signalling

Answer 15

1. Agonist-bound receptor binds to G protein
2. GDP released from alpha subunit (GDP➡️GTP)
3. GTP binds to alpha subunit
4. α-βγ complex dissociated into α-GTP and free βγ and each can interact with effector proteins
5. GTPase hydrolyses GTP➡️GDP (5secs)
6. α-GTP and βγ subunits reform an inactive heterotrimeric complex

Question 16

What govern receptor-G protein selection

Answer 16

Gα subunit is a primary determinant

Question 17

Three G protein types

Answer 17

Gα(s)- stimulates adenylyl cyclase
Gα(i)- inhibits adenylyl cyclase
Gα(q)- stimulated phospholipase C

Question 18

Difference between endogenous and exogenous ligands

Answer 18

Endogenous: Natural ligands
E.g.) noradrenaline, adrenaline

Exogenous: Synthetic ligands
E.g.) isoprenaline, salbutamol, propranolol