Molecular cell biology

Question 1

What are ionotropic receptors?

Answer 1

Ligand-gated ion channel

Ion channel opens in response to binding of specific ligands to extracellular sites

Question 2

The main excitatory neurotransmitter in the CNS?

Answer 2

Glutamate

Question 3

The main inhibitory neurotransmitter in the CNS?

Answer 3

GABA

Question 4

What are the two main types of Ach receptors?

Their features?

Answer 4

Nicotinic receptors

• G protein coupled
• Slow metabolic response

Muscarinic receptors

• Ligand-gated ion channels
• Fast synaptic transmission

Question 5

How are Nicotinic Ach receptors arranged? (molecular make-up)

Answer 5

5 subunits arranged around a central channel

Have 2 or more alpha subunits

Question 6

What are the two main types of nicotinic receptor sub-units?

Answer 6

Heteromeric (different subunits - at least to alpha)

Homomeric (one subuit - has to be one type of alpha)

Question 7

How do non-depolaraising muscle relaxants work?

Answer 7

Block neuromuscular transmission by binding competitively at the agonist site on the muscular nAChR.

Question 8

Two main types of ionotropic glutamate receptors?

Answer 8

NMDA receptor

AMPA receptor

Question 9

What drug specifically binds to NMDA receptors?

Answer 9

Ketamine

Question 10

Main effects of GABA on the brain, specifically in the amygdala?

Answer 10

Calming effects (amygdala commonly associated with emotion)

Question 11

Two types of GABA receptors?

Answer 11

GABAa - ionotropic

GABAb - metabotropic (G-protein coupled)

Question 12

Results of activation of a GABA receptor?

Answer 12

Influx of Cl- thereby inhibiting the neurone

Question 13

The molecular makeup of a GABA receptor?

Answer 13

Heteropentameric (5 different subunits)

Question 14

Common drugs that act on the GABA receptor?

How do they work?

Answer 14

Benzodiazepines, sedatives e.g. phenobarbital, barbituates

They bind on a different subunit to the one that GABA binds on but increase GABA’s action.

Question 15

How do benzodiazepines increase GABA’s action?

Answer 15

They lock the GABA receptor into a position where GABA has a much higher affinity for the GABA receptor.

Question 16

How do the two glutamate receptors AMPA and NMDA interact?

Answer 16

AMPA is activated my small amounts of glutamate release, whereas NMDA is not, it is blocked by a magnesium ion.

AMPA receptors let Na+ into the post-synaptic membrane, depolarising it (as usual)

If there is a large enough glutamate release the NMDA receptor will be activated and the magnesium plug removed

NMDA receptors also let Ca2+ into the post-synaptic membrane, the Ca2+ has a number of secondary effects and increases the post-synaptic membranes ability to be depolarised. It does this through:

• Increasing the amount of AMPA receptors
• Phosphorylates AMPA receptors (increases the amount of Na+ that can travel in)

Synapse is said to be enhanced

This contributes to long term potentiation