Ligand Gated Ion Channel Receptors

Question 1

give examples of LGICRs

Answer 1

nicotinic acetylcholine receptors (nAchR)

Question 2

what is a LGICR?

Answer 2

• receptors that dictate the reaction produced by a chemical

- binding of a chemical causes an ion path to open

Question 3

what are other types of LGICRs and what are their agonists?

Answer 3

• nicotinic cholinoceptor: Ach
• 5HT3: 5-HT
• GABAa: γ aminobutyric acid (GABA)
• glycine: glycine

Question 4

how many agonist molecules must bind to the LGICR for them to open?

Answer 4

2

Question 5

describe the structure of the LGICR

Answer 5

• pentamer: each LGICR made of 5 similar proteins that form a pore
• each has 4 transmembrane domains
• 2nd TM forms the pore
• some aa on the polypeptide chain are hydrophobic/philic so they may exist above the membrane
• has 20 transmembrane domains in total

Question 6

describe the structure of a nAchR on a skeletal muscle

Answer 6

• has 8 α subunits, 5 β subunits, 1 γ subunit and 1 δ subunit

Question 7

what are the 2 types of nAchR

Answer 7

• Nm or N1 (on muscles)

- Nn or N2 (CNS & autonomic ganglia)

Question 8

describe the composition of nAchR N1

Answer 8

• in adults: α1-ε-α1-β1-δ

- in foetus: α1-γ-α1-β1-δ

Question 9

describe the composition of nAchR N2

Answer 9

α2-α8 and β2-β4

Question 10

what happens when Ach binds to a nAchR?

Answer 10

• causes an excitatory junction potential
• influx of Na+
• stimulates an AP

Question 11

what happens to Ach when it is released from the nAchR?

Answer 11

it is degraded and causes the membrane potential to go back to baseline

Question 12

what is myathesia gravis?

Answer 12

• it is an autoimmune disease where muscle nAchRs are degraded
• targets the α1 subunit
• symptoms: muscle weakness, fatigue, drooping eyelids

Question 13

what do GABAa and glycine receptors do?

Answer 13

• inhibit activity
• allows influx of Cl-
• causes hyperpolarisation