MT1 PP Open Questions

Question 1

The open probability of an ion channel can range from __ to __

Answer 1

0 to 1

(or 0 to 100%)

Question 2

Ion channels are protein pores that span the _____

Answer 2

plasma / bilipid membrane

Question 3

The protein segment responsible for K channel selectivity is called the ____

Answer 3

P loop

Question 4

The selectivity filter of a K+ channel is located close to the ____ side

Answer 4

extracellular

Question 5

The central cavity of an ion channel communicates with
which solution through the gate?

Answer 5

Intracellular solution

Question 6

During N-type inactivation, the N terminal peptide segment of a voltage gated K channel plugs its pore from the _______ side

Answer 6

intracellular

Question 7

ATP-sensitive K+ channels are involved in regulation of which hormone?

Answer 7

Insulin secretion from pancreatic beta cells

Question 8

Type II diabetes mellitus can be treated by sulphonylureas. What effect do they have on the ATP-sensitive K+ channels:

Answer 8

Sulfonylureas (tolbutamide) inhibit the ATP-sensitive K+ channels by binding to the SUR1 subunit in pancreatic beta cells. Inhibiting the channel leads to easier depolarization and insulin release from the beta-cells – which can lower blood sugar level.

Question 9

At high ionic concentrations the ion channel throughput rate becomes:

Answer 9

saturated

Question 10

The gate of a K+ channel is located close to the ____ side

Answer 10

intracellular

Question 11

Which transmitter is released from the motoneurons stimulating muscle contraction?

Through which receptor is it mediated?

What second messenger is essential for the above process?

Answer 11

acetycholine

nicotinic acetycholine receptor

Ca2+ is second messenger

Question 12

List the names of the intermediates that are produced in the consecutive steps of noradrenaline synthesis

Answer 12

Tyrosine -> DOPA -> dopamine -> noradrenaline

Question 13

How does dopamine influence (decrease, increase, or no effect) the kidney:

• effect on Na+/K+ ATP-ase
• rate of Na+ reabsorption

Answer 13

decrease for both

Question 14

Name the metabolite that is formed in the brain in the metabolism of noradrenaline and can be detected in the urine

Answer 14

MHPG

3-Methoxy-4-hydroxyphenylglycol

Question 15

Name a hormone that stimulates the activity of Na+,K+ ATPase

Answer 15

Norepinephrine

Also Aldosterone

Question 16

Which protein regulates the CFTR channel?

Answer 16

PKA

Question 17

Phosphorylated CFTR Cl- channels require intracellular _____ for gating

Answer 17

ATP

Question 18

Under physiological conditions, ATP-sensitive K+ channels are activated by intracellular ____ and inhibited by intracellular ____

Answer 18

ADP / ATP

Question 19

Phosphorylation by cAMP dependent protein kinase _______ the activity of CFTR Cl- channel

Answer 19

Increases

Question 20

For this reaction, name the substrates and products

What’s the enzyme?

Where is the enzyme (cell type and intracellular compartment)?

Answer 20

Substrates: choline + acetyl-CoA

Products: Acetylcholine + CoA-SH

Enzyme: choline acetyltransferase (ChAT)

Location: cytosol of cholinergic axon terminal

Question 21

Indicate one therapeutical means by which the synthesis of noradrenaline can be decreased

Answer 21

α-metil-DOPA is similar to DOPA, used as substrate of the same enzyme -> α-methylnorepinephrine, by dopamine beta-hydroxylase. This product is effective but not as much as norepinephrine.

Question 22

What is the name of the enzyme that hydrolyzes acetycholine in the cholinergic synapse?

What kind of molecules exert an irreversible inhibition of this enzyme?

What is the underlying effect of the irreversible inhibition of the enzyme by those molecules?

Answer 22

Acetylcholinesterase

Organophosphates, i.e. DFP, Sarin gas. Makes pesticides and chemical weapons.

Phosphorylates a serine group of Ach-esterase, making it unable to function and this cannot be undone (at least in the CNS, the antidote for this only works in the periphery). The action of acetylcholine on nerve terminals becomes continuous, so both constant muscarinic and nicotinic effects.

Question 23

ATP-sensitive K+ channels are heterooctamers formed by four inward rectifier K+ channel subunits and four ______ subunits

Answer 23

ATP-sensitive K+ channels are heterooctamers formed by four inward rectifier K+ channel subunits and four SUR (sulfonylurea receptor) subunits

Question 24

What is the name of the enzyme catalyzing the final step in the synthesis of noradrenaline?

What is the intracellular localization of this enzyme?

What is the substrate of this enzyme?

Answer 24

1. Dopamine Hydroxylase
2. inside the vesicles
3. Dopamine

Question 25

1. What is the primary molecular target of strophanthin in the human body?
2. What is the sequence of events leading to positive inotropic effect of strophantin?

Answer 25

1. Na+/K+ ATPase
2. Moderate inhibition of Na+/K+ ATPase causes an increase in intracellular sodium, which reverses the function of Na+/Ca2+ antiporter, causing sodium to leak out and calcium to leak into the heart cell, causing an increase in inotropy/ contractility

Question 26

Answer the following questions below concerning nicotinic receptors:

1. In which organs are they present?
2. What happens in the cells due to stimulation of nicotinic receptors?
3. What is the subunit composition of the receptor?
4. What is the name of the autoimmune disease that is characterized by an impaired function of nicotinic receptors?

Answer 26

1. Present in skeletal muscle, autonomic ganglia, CNS
2. Causes depolarization by increasing permeability to sodium and potassium
3. 2 alpha, 1 beta, 1 gamma, 1 delta subunits
4. Myasthenia Gravis