MT1 PP MCQ

Question 1

Structure of the K+ channel

a) Dimer
b) Trimer
c) Tetramer
d) Pentamer

Answer 1

c)Tetramer

Question 2

How can we explain the saturation of ion-channel throughput rates at high ion concentrations?

A. By an active transport mechanism

B. At high ion concentrations the throughput rate becomes diffusion limited

C. By passive diffusion through a cylindrical hole

D. The pore contains binding sites for the permeant ion; at high ion concentrations the off-rate of the ion from its binding site becomes rate limiting
E. None of the above provides an explanation

Answer 2

B. At high ion concentrations the throughput rate becomes diffusion limited

Question 3

Which of the following statements are true for ion-channel gating?

1. Gating is a stochastic process
2. Gating is a deterministic process
3. Rate constants describe the probabilities of transition between stable open and closed conformations
4. Gating schemes describe well the kinetics of ionic currents of the whole cell membrane
5. Gating schemes are only useful for describing kinetics of single ion channels

A: 2,4

B. 1,3,5

C. 1,3,4

D. 3,4

E. 5

Answer 3

C: 1,3,4

Question 4

Which statements are true?

1. At normal [Na+]e.c. and [K+]i.c. the activity of the Na,K ATPase is less than 15% of its maximal activity
2. When action potential is formed, the activity of the Na,K ATPase increases 25 fold
3. Corticosteroids decrease the expression of Na,K ATPase in the kidney
4. Dopamine activates the Na,K ATPase in the kidney
5. Epinephrine activates the Na,K ATPase in the skeletal muscle

A. 1,2,3 B. 1,2,4

C. 2,4,5 D. 3,4,5

E. 1,2,5

Answer 4

E. 1,2,5

Question 5

Which hormones/neurotransmitters stimulate the activity of the Na,K-ATPase in a tissue-specific manner?

1. Dopamine
2. Norepinephrine
3. Insulin
4. Aldosterone
5. Epinephrine

A: 1,2,3,4 B: 2,3,4,5

C: 1,3,4 D: 1,2,4,5

E: All

Answer 5

B: 2,3,4,5

(Dopamine, as far as I know, does not ever stimulate but only inhibits Na,K-ATPase. This is another hard one to answer confidently)

Question 6

Which statements are valid for the Na+-H+ exchanger?

1. Due to its action the pH in the cells is higher than the extracellular pH
2. It pumps Na+ and H+ against their electrochemical gradient
3. Its inhibiton diminishes the resting membrane potential
4. It takes part in the maintenance of pH gradient between the vesicles and the cytoplasm
5. Its action results in decreased sodium reabsorption in the kidney

A: 1,2,4 B: 1,4,5

C: 2,3,4 D: 2,4,5

E: none

Answer 6

E: none

Question 7

Which of the statements are valid?

1. Choline is formed from acetylcholine by choline acetyltransferase
2. The choline uptake is mediated by the so-called “low-affinity choline transporter”
3. Na+-cotransporters inactive acetylcholine in cholinergic synapses
4. The uptake of acetylcholine into the synaptic vesicles is an ATP-dependent process
5. Acetylcholine esterase can be inhibited by atropine

A: 1,2,4 B: 2,3,5

C: 2,4 D: 1,3,4

E: 2,5

Answer 7

C: 2,4

(1, 3, and 5 are definitely false, and 4 is definitely true, so process of elimination leads to this answer. On choline uptake affinity transporters, the slides say the low affinity ones are in all tissues, but the high affinity ones are only in cholinergic neurons)

Question 8

Which of the following factors has no role in the cellular effects of muscarinic receptor activation?

A. Increase of intracellular Ca2+ concentration

B. Activation of phospholipase C

C. Na+ uptake

D. Activation of K+ channel

E. Activation of G protein

Answer 8

C. Na+ uptake

Question 9

Which of the listed interrelations are valid for the following 2 statements:

1. Dopamine beta hydroxylase is localized in the vesicles of noradrenergic axon terminals
2. Dopamine is formed in the synaptic vesicles

A. Statements 1 and 2 are both valid, and 2 is the consequence of 1

B. Statements 1 and 2 are both valid, but there is no causative relation between them

C. Statement 1 is valid, but statement 2 is not

D. Statement 2 is valid, but statement 1 is not

E. Neither statement is valid

Answer 9

C. Statement 1 is valid, but statement 2 is not

(NE is formed in the vesicles, not dopamine)

Question 10

Which of the following listed interrelations are valid for the following two statements:

1. Monoamine oxidase is localized in the outer mitochondrial membrane
2. Deprenyl inhibits monoamine oxidase

A. Statements 1 and 2 are both valid, and 2 is the consequence of 1

B. Statements 1 and 2 are both valid, but there is no causative relation between them

C. Statement 1 is valid, but statement 2 is not

D. Statement 2 is valid, but statement 1 is not

E. Neither statement is valid

Answer 10

B. Statements 1 and 2 are both valid, but there is no causative relation between them

(presumably this is the answer, unless there’s something more complicated about the mechanism of deprenyl that they didn’t explain where it only works bc MAO is in the outer mitochondrial membrane. it’s a shitty question)

Question 11

Which statements are true concerning the nicotinic acetylcholine receptor channel?

1. The channel is a homopentamer, its dysfunction can lead to myasthenia
2. The channel is a heteropentamer, its dysfunction can lead to myasthenia
3. The channel is a tetramer, its dysfunction can lead to myotonia
4. The ligand-binding domain is a 4-fold symmetrical gating ring
5. The ligand-binding domain is a 5-fold symmetrical ring

A. 1,5 B: 2,5

C: 3,4 D: 1

E: 2

Answer 11

B: 2,5

(PROBABLY this answer anyway, this is according to questions asked to a professor about it. Apparently the binding unit is a homopentamer but the whole channel is a heteropentamer… This is so fucking stupid)

Question 12

Answer 12

B: 1,3,4,5

(They never talked about it, but non-selective ion channels do exist.. unless our biochem department doesn’t believe in them. 1,3,4 are definitely true and were covered though.)

Question 13

Which plasma membrane calcium ATPase is predominantly neuronal?

A. PMCA1

B. PMCA2

C. PMCA3

D. PMCA4

E. PMCA5

Answer 13

B. PMCA2

(During the lecture, I’m pretty she said we don’t need to know the specifics of this, yet it’s on past papers)