Receptor mechanisms I

Question 1

A chemical is nothing without its

Answer 1

Receptor

Question 2

What happens when a hormone/neurotransmitter binds to specific receptor

Answer 2

There will be an effect in that cell

Question 3

What will an antagonist do

Answer 3

Will have no effect on the cell and it stops the receptor from working

Question 4

What is the order of speed from fastest to slowest when it comes to receptors

Answer 4

1. Ligand gated ion channels
2. G-protein coupled
3. Tyrosine kinase linked and nuclear receptors

Question 5

What is the receptor of a ligand gated ion channel

Answer 5

Its an ion channel

Question 6

What does binding of an agonist cause on a ligand gated ion channel

Answer 6

Causes a conformational change, opening the ion channel, creating an instant ion flow

Question 7

What is a nicotine cholinoreceptor stimulated by

Answer 7

Acetylcholine

Question 8

What is a 5HT3 receptor stimulated by

Answer 8

5-HT (serotonin)

Question 9

What ions do the nicotine cholinoreceptor and the 5HT3 receptor use and what happens to the membrane potential

Answer 9

They both use Na and Ca

The membrane potential depolarises (-70mv to 0mv)

Question 10

What is the GABAa receptor stimulated by

Answer 10

gamma-aminobutyric acid (GABA)

Question 11

What is the glycine receptor stimulated by

Answer 11

Glycine

Question 12

What ion does the GABAa and glycine receptor use and what happens to the membrane potential

Answer 12

They both use Cl

The membrane hyperpolarises

Question 13

What is the structure of the basic protein forming the parts of the ligand gated ion channel

Answer 13

• Big amino terminus
• 4 transmembrane domains
• 2nd domain is differentiated from the other 3

Question 14

What does a functional ligand gated ion channel require

Answer 14

• 5 of these grouped domains, so overall there are 20 domains
• The second domain group is situated in the middle and therefore forms the ion pathway

Question 15

How is the structure of the ligand gated ion channel related to its function

Answer 15

Hydrophilic amino acids are on the outside of the plasma membrane
Hydrophobic/lipophilic amino acids are on the inside of the plasma membrane, therefore the transmembrane domains will be hydrophobic amino acids

Question 16

How many molecules are required to open the pentamer

Answer 16

2 molecules of agonist e.g. acetylcholine

Question 17

Where are N1/Nm nicotinic receptors found

Answer 17

They are found in motor end plates on skeletal muscle cells in the neuromuscular junction

Question 18

Where are N2/Nn nicotinic receptors found

Answer 18

Found in cholinergic and adrenergic ganglia, the CNS and the adrenal medulla

Question 19

Whats the difference between adult and foetal N1 muscle nicotinic receptors and why

Answer 19

Foetal ion channel takes longer to open and close since it has gamma subunit instead of an epsilon subunit (Alpha-1, gamma, alpha-1, beta-1 and delta)

Question 20

What is the cause of Myasthesia gravis

Answer 20

Antibodies attack the alpha-1 subunit in N1 muscle nicotinic acetylcholine receptors causing the number of functioning receptors to drop. N2 neuronal nicotinic receptors are unaffected

Question 21

What are the diagnosable differences of Myasthesia gravis

Answer 21

The electrical recording of the resting potential in the neuromuscular junction presents with very little miniature end plate potentials

Question 22

What are the symptoms of Myasthesia gravis

Answer 22

Muscle weakness, dropping eyelids, fatigue, difficulty swallowing

Question 23

What does the GABAa receptor do once stimulated

Answer 23

causes an inhibitory effect on neurotransmission by diminishing the chance of a successful action potential occurring