CMB1004/L15 Cell Signalling I

Question 1

What is the purpose of ion channel coupled receptors?

Answer 1

Alters membrane permeability to ions

Question 2

What is the purpose of G-protein coupled receptors?

Answer 2

Interacts with G-proteins in cell membrane

Question 3

What is the purpose of enzyme coupled receptors?

Answer 3

Intrinsic enzyme activity or associates with an enzyme to catalyse reaction

Question 4

Give an example of an ion channel coupled receptor.

Answer 4

Any synaptic receptors

Question 5

Describe the action of a nitotinic acetylcholine receptor. (6)

Answer 5

ACh binds to receptor
Conformational change
Na+ enter cell
Depolarisation
T-tubules carry depolarisation to sarcoplasmic reticulum
Ca2+ release causes muscle contraction

Question 6

What is myasthenia gravis? (3)

Answer 6

Autoimmune condition
Causes muscle weakness
Autoimmune response to nicotinic ACh receptors

Question 7

How many times do G-protein coupled receptors pass through the membrane?

Answer 7

7

Question 8

What are trimeric G-proteins?

Answer 8

Transduce signals from G-protein linked receptors

Question 9

What are monomeric G-proteins?

Answer 9

Transduce signals from enzyme linked receptors

Question 10

What is the role of G-proteins?

Answer 10

Transducers

Question 11

What is bound by G-proteins?

Answer 11

GTP (active)
GDP (inactive)

Question 12

How many subunits make up trimeric G-proteins?

Answer 12

3 heterologous subunits
A, B and G

Question 13

What occurs as soon as a signal molecule bind a G-protein linked receptor?

Answer 13

Conformational change to receptor and alpha subunit
Alpha subunit released GDP and binds GTP

Question 14

How do G-proteins transduce signals?

Answer 14

By binding other target proteins on plasma membrane

Question 15

How do G-proteins inactivate?

Answer 15

GTP hydrolysis

Question 16

What are the 2 key proteins activated by trimeric G-proteins?

Answer 16

Adenylyl cyclase
Phospholipase C

Question 17

What are the secondary messengers to (1) adenylyl cyclase and (2) phospholipase C?

Answer 17

(1) Cyclic AMP (cAMP)
(2) Inositol 1,4,5-triphosphate (IP3) and Diacyllycerol (DAG)

Question 18

What is the role of adenylyl cyclase?

Answer 18

Converts ATP to cAMP

Question 19

What is the main role of cAMP?

Answer 19

Activation of cAMP-dependent protein kinase (PKA)

Question 20

What occurs when cAMP binds to PKA?

Answer 20

Conformational change
Release and activation of catalytic subunits

Question 21

Give the 5 steps to G-protein coupled receptor activation.

Answer 21

1. Activation of G-protein
2. G-protein activated adenylyl cyclase
3. Adenylyl cyclase converts ATP to cAMP
4. cAMP activates protein kinase A
5. PKA phosphorylates other proteins

Question 22

Give 3 roles of GTP and ATP in the cell.

Answer 22

Nucleic acid synthesis
Signal transduction
Carrying energy