Calcium & G-coupled Receptors Flashcards Preview

Cell Physiology & Pharmacology > Calcium & G-coupled Receptors > Flashcards

Flashcards in Calcium & G-coupled Receptors Deck (53)
Loading flashcards...
1

In regards to the movement of ions, how an Na+ K+ ATPase functions?

3 Na+ ions out, 2 K+ ions in

2

Describe, in simple terms, the structure of PKA.

A combination of 4 subunits - 2 r subunits to which cAMP binds, and 2 c subunits which are the catalytic entity

3

List 3 ion transporters used to remove Ca2+ from the cell. Are these ion transporters passive or active transporters?

Plasma membrane Ca2+ ATPase (PMCA) - active
Smooth Endoplasmic Reticulum Ca2+ ATPase (SERCA) - active
Na+ Ca2+ Exchanger (NCX) - passive (antiporter)

4

What effect do agonists have on a receptor? In that case, what effect do antagonists have on a receptor?

Agonists activate a receptor - antagonists do not activate a receptor

5

Describe the structure of a G-protein coupled receptor?

A single polypeptide chain spanning the membrane 7 times - it has an extracellular N-terminus and an intracellular C-terminus

6

Describe the steps explaining how a substrate may activate a G protein.

The substrate binds the G protein-coupled receptor at either the N-terminus or by burying itself in the membrane of the receptor - this causes a conformational change in the receptor which releases the G protein - this causes the G protein to release GDP and bind GTP

7

What type of G-protein activates phospholipase C? What does phospholipase C catalyse?

Phospholipase C is actives by a Gq-type G-protein, and catalysts the cleavage of PIP2 to IP3 and DAG

8

What type of G-protein activates adenylyl cyclase? What type inhibits it?

Adenylyl cyclase is activated by Gs-type G-proteins, and is inhibited by Gi-type G-proteins

9

What molecules make up a G-protein?

A G-protein contains an alpha, beta, and gamma subunit (is heterotrimeric) - the beta and gamma subunits functionally act as one however

10

What cation is required for neurotransmitter release?

Ca2+ entry

11

What is the neuromuscular junction?

The synapse between a nerve and a skeletal muscle fibre (cell)

12

Are Ca2+ levels higher intracellularly or extracellularly?

Extracellularly

13

What is needed to increase the amount of Ca2+ entry at a nerve terminal?

Increase in frequency (as opposed to amplitude) of action potentials

14

What is the pore-forming subunit of a voltage-gated Ca2+ channel?

A1 (alpha 1) subunit

15

How many subunits does a voltage-gated Ca2+'channel have? How does this relate to a voltage-gated Na+ channel?

Both have 4 subunits, and share a very similar structure

16

What molecules can block L-type Ca2+ channels? Can you give 1 example?

DHP (dihydropyridines) e.g. nifedipine

17

What type,of Ca2+ channels are found in the heart?

R-type and T-type

18

How does increased intracellular Ca2+ affect Ca2+ channels?

Increased intracellular Ca2+ channels block the activity of Ca2+ channels

19

How do voltage-gated Ca2+ channels act in comparison to voltage-gated Na+ channels?

They act in a slower manner

20

What type of Ca2+ channels are found in skeletal muscle?

L-type

21

What breaks down acetylcholine in the synaptic cleft?

Acetylcholinesterase

22

What molecule brings Ca2+ vesicles to the pre-synaptic member ae to be released?

Synaptotagmin

23

What complex is associated with fusion of the Ca2+ vehicle to form a pore in the pre-synaptic membrane?

The SNARE complex

24

What molecules does a nicotinic acetylcholine receptor let pass through its pore?

Na+ and K+

25

How many molecules of acetylcholine are required to induce a conformational change and open a nicotinic acetylcholine receptor?

2 molecules of acetylcholine

26

If a nicotinic acetylcholine receptor lets through both Na+ and K+, which does Na+ flood into the cell and not K+?

The resting membrane potential of a cell is much closer to the equilibrium potential of K+ - as it is much further from the equilibrium potential of Na+, Na+ floods into the cell in an effort to reach equilibrium, which leads to depolarisation of the cell

27

State an example of a competitive nicotinic acetylcholine receptor blocker.

Tubocurarine

28

How can a competitive blocker of a nicotinic acetylcholine receptor (such as tubocurarine) be overcome?

Increasing the amount of acetylcholine (or the receptors endogenous substrate)

29

How do depolarising blockers act at nicotinic acetylcholine receptors?

They act to keep nicotinic acetylcholine receptors in a depolarised state, thereby deactivating adjacent Na+ channels meaning an action potential cannot propagate

30

Can you list an example of a depolarising nicotinic acetylcholine receptor blocker?

Succinylcholine