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Biochemistry > Semester 3, midterm 1: Extra q's > Flashcards

Semester 3, midterm 1: Extra q's Flashcards

1
Q

The sodium potassium pump is found in:

a) Striated muscle
b) Brain
c) PNS
d) Heart
e) Testis

A

All solutions are correct

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2
Q

In order for sodium potassium ATPase to operate properly:

a) Both sodium and potassium are required
b) Potassium must saturate the site that it binds to
c) Potassium does not need to saturate the site that it binds to
d) Less than 50% of sodium binding sites are required to be filled with sodium
e) More than 50% of sodium binding sites are required to be filled with sodium

A

a, b, d (?)

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3
Q

Postganglionic sympathetic nerves containing nordadrenaline are found in:

a) Heart atria
b) Heart ventricles
c) Intestinal smooth muscle
d) Blood vessels
3) Bronchi

A

All solutions are correct

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4
Q

What is the subunit composition of the ganglionic type nicotinic receptor?

a) A2b3
b) A3b2
c) A2b2
d) A1b4
e) None of the above

A

a

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5
Q

Which plasma membran calcium ATPase is predominently neuronal?

a) PMCA1
b) PMCA2
c) PMCA3
d) PMCA4
e) PMCA5

A

b

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6
Q

Which alpha subunit of the sodium potassium ATPase is the only one found in epithelial cells?

a) a1
b) a2
c) a3
d) a4
e) a5

A

a

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7
Q

Which activates adenylate cyclase directly?

a) a subunit of Gs protein
b) cAMP
c) cyclic phosphodiesterase
d) diacylglycerol (DAG)
e) a subunit of Gq protein

A

a

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8
Q

Which factor is NOT involved in the muscle contraction following signal transmission in the neuromuscular junction?

a) Ryanodine receptor
b) Dihydropyridine receptor
c) Nicotinic receptor
d) Beta receptor
e) L-type Ca2+ channel

A

d*

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9
Q

Which factor is involved in the efflux of Ca2+ from the mitochondria?

a) Ca2+ uniporter
b) IP3 receptor
c) Na/Ca exchange
d) T-channel
e) Ryanodine receptor

A

c?

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10
Q

Which of the following receptors function as Ca2+ channels?

a) Nicotinic receptor in skeletal muscle
b) a1 receptor of smooth muscle in the blood vessel wall
c) NMDA receptor in the CNS
d) D2 receptor in the striatum
e) Muscarinic receptor in the heart

A

c*

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11
Q

Which Ca2+ channel is rapidly inactivated in the heart?

a) L-type
b) N-type
c) P-type
d) T-type

A

d ?*

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12
Q

Which statement is true concerning the malignant hyperthermia?

a) Characterized by rigidity of skeletal muscle
b) It is a consequence of abnormal CNS thermoregulation
c) It is a consequence of a mutation of the ryanodine receptor
d) It can be treated with Ca2+ channel blocker
e) It is accompanied by intensive lactate production in the muscle

A

a, c, e*

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13
Q

The reaction catalyzed by DOPA decarboxylase:

a) L-dopa -> dopamine
b) Dopamine -> noradrenaline
c) Serotonin -> 5-hydroxy-indoleacetate
d) 5-hydroxy-tryptophan -> serotonin
e) Tryptophan -> 5-hydroxytryptophan

A

a, d*

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14
Q

Which statements are true concerning the nicotinic acetylcholine receptor channel?

a) the channel is a homopentamer, its disfunction can lead to myasthenia
b) the channel is a heteropentamer, its disfunction can lead to myasthenia
c) the channel is a tetramer, its disfunction can lead to myasthenia
d) the ligand binding domain is a 4 fold symmetrical gating ring
e) the ligand binding domain is a 5 fold symmetrical ring

A

a, e*

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15
Q

ATP-sensitive K channels are heteroctamers formed by four inward rectifier K+ channel and four ……. subunits.

A

SUR

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16
Q

Under physiological conditions ATP-sensitive K+ channels are activated by intracellular …….. and inhibited by intracellular …………..

A

ADP, ATP

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17
Q

Type II diabetes mellitus can be treated by sulphonylureas, which ………….. ATP-sensitve K+ channels

A

closes (inhibits)

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18
Q

ATP-sensitive K+ channels are involved in the regulation of the hormone ……..

A

Insulin

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19
Q

What is the name of the enzyme that hydrolyses acetylcholine in the cholinergic synapse?

A

Acetylcholinesterase

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20
Q

What kind of molecule exerts irreversible inhibition of the enzyme acetylcholinesterase?

A

Diisopropyl flourophosphate (DFP)

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21
Q

What is the underlying effect on the irreversible inhibition of the enzyme by the above mechanisms? (by DFP)

A

Increased acetylcholine in synaptic cleft and prolonged action of cholinergic fibers and decreased production of acetylcholine (?)

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22
Q

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

A

Dopamine hydroxylase

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23
Q

What is the intracellular location of this enzyme? (dopamine hydroxylase)

A

synaptic vesicles in adrenal medulla

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24
Q

What is the substrate of dopamine hydroxylase?

A

Dopamine

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25
Q

What is the primary molecular target of strophantine in the human body?

A

Sodium potassium ATPase

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26
Q

What is the sequence of events leading to positive inotropic effect of strophantine?

A

It inhibits Na/K-ATPase -> Na conc. increases IC -> reverse function of Ca/Na pump -> Ca2+ IC increased -> positive inotropic effect

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27
Q

In which organs are nicotinic acetylcholine receptors present?

A

Skeletal muscle, autonomic ganglia

28
Q

What happens in the cells due to stimulation of nicotinic receptors?

A

Na+ entry, K+ efflux, or depolarization

29
Q

What is the subunit composition of the nicotinic receptors?

A
  • 2alpha2beta gamma
    OR
    Neuronal: 2alpha3beta / 5alpha
    Muscular: Adults- 2alpha,beta,epsilon,delta
    Baby- 2alpha, beta, gamma, delta
30
Q

What is the name of the autoimmune disease that is characterized by an impaired function of the nicotinic receptor?

A

Myasthenia Gravis

31
Q

The central fatigue in exercise is related to the decreased levels of ………. (Major excitatory neurotransmitter)

A

Glutamate

32
Q

The central fatigue is related to elevated levels of …… produced from tryptophan

A

Serotonin

33
Q

….elevated levels of serotonin, produced from tryptophan, the neural uptake of which is favored by the decreased blood levels of ……… amino acids consumed by the working muscle

A

Branched chain amino acids

34
Q

Following neural stimulation in skeletal muscle, Ca2+ binds to …….. to initiate contraction, to …….. , subunit of …………. to initiate glycogen breakdown and to phosphatase subunit of ……… to initiate oxidation of pyruvate

A

Troponin C, calmodulin, phosphorylase kinase, pyruvate dehydrogenase complex

35
Q

In liver insufficiency ….. concentration is elevated and toxic for the brain.

A

Ammonia

36
Q

Inhibition of ………. enzyme prevents accumulation of ……… in astrocytes

A

Glutamine synthase, glutamine

37
Q

The most serious problems in acute liver insufficiency (3):

A
  • Hypoglycemia
  • Hyperammonemia
  • Lactic acidosis
38
Q

Where can information on membrane topology of an ion channel be innferred from?

A

Hydropathy plots

39
Q

Membrane depolarization activates voltage-gated channels by increasing their …..

A

Open probability

40
Q

The open probability of an ion channel is the ……… spent in the open state

A

Fraction of time

41
Q

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

A

0 to 1

42
Q

The gating charge in the voltage sensor of voltage-gated K+ channels is provided by conserved ……. residues on the S4 helix

A

Arginine and lysine

43
Q

How do the the following factors change (decrease, increase, no change) as a consequence of decreased activity of Na-K-ATPase?

  • Intracellular Na+ ?
  • Intracellular pH ?
  • Glucose uptake of skeletal muscle cells from plasma?
A

Increase, decrease, no change

44
Q

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

A

Synthesis can be inhibited completely by alpha-methyl-P-tyrosine (used in adrenal medulla cancer)

45
Q

1) Which neurotransmitter is released from the motor neurons stimulating contraction?
2) Through which effect is this effect mediated?
3) What is the second messenger essential for the above effect?

A

1) Acetylcholine
2) Nicotinic acetylcholine receptors
3) increase in intracellular Ca2+

46
Q

How does dopamine influence the kidney?

  • Activity of Na/K-ATPase
  • Rate of Na reabsorption
A

Dopamine inhibits Na/K-ATPase in the BL mem.

Decreases Na reabsorption

47
Q

Name the main metabolite formed in the brain in the NE metabolism, which can be detected in urine

A

3-methoxy-4-hydroxy-phenylglycol (MHPG)

48
Q

Name the hormone thats stimulates Na/K-ATPase

A

Aldosterone

49
Q

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

A

Pore loop (located extracellularly)

50
Q

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

A

Extracellular side

51
Q

The central cavity communicates with which solution through the gate?

A

Intracellular solution

52
Q

Which technique reveals openings and closure of individual ion channel pores?

A

Patch clamp technique

53
Q

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

a) Gating is a stochastic process
b) Gating is a deterministic process
c) Rate constants describe the probabilities of transition between stable open and closed conformations
d) Gating schemes describe well the kinetics of ionic currents of the whole cell membrane
e) Gating schemes are only useful for describing kinetics of single ion channels

A

a, c, d*

54
Q

Which disease is caused by a mutation of the clc Cl-channel?

a) Muasthenia
b) Myotonia
c) Epilepsy
d) Cystic fibrosis
e) Long QT syndrome

A

b

55
Q

Which disease is caused by a mutation in the CFTR Cl-channel?

a) Myasthenia gravis
b) Myotonia
c) Cystic fibrosis
d) Epilepsy
e) Long QT syndrome

A

c*

56
Q

Na/K-ATPase is electrogenic because

a) Hydrolyzes ATP
b) Pumps more K into the cell than Na out of the cell
c) Mem. pot. favors pumping Na out of the cells
d) Hydrolyzing one ATP, 3Na pumped out, 2K in
e) Pumping out of Na causes depolarization

A

d*

57
Q

Which of the following statements explain the relatively specific effect of strophantin on the heart?

a) Na/Ca exchanger is formed only in the heart
b) Na/K-ATPase alpha subunit found in the heart binds strophantin with the lowest affinity
c) Strophantin binds to Na/K-ATPase intracellularly in the heart
d) The Kd of Na/K-ATPase alpha subunit for strophantin is the lowest in the enzyme found in the heart
e) Strophantin can inhibit only the heart muscle Na/K-ATPase

A

d*

58
Q

Which of the following statements are valid?

a) The high-affinity choline transporter is found exclusively in cholinergic terminals
b) All types of cholinergic receptors belong to the family of seven TMD receptors
c) The nicotinic receptor is an ion channel permeable for Na and K
d) The inhibition of Ach esterase decreases the Ach content of synaptic vesicles

A

a, c*

59
Q

The movement of how many unitary charges precedes activation of a voltage-gated K-channel?

a) 0.1-0.2
b) 1-2
c) 4-6
d) 12-16
e) 40-60

A

d*

60
Q

What is true for the subunit composition of voltage-gated Cl channels?

a) Two-pore dimers, both polypeptide chains contribute to forming both pores
b) Two-pore dimers, each polypeptide chain individually forms a pore
c) Single-pore dimers, both polypeptide chains contribute to forming the pore
d) Single-pore tetramers
e) Single-pore monomers

A

b*

61
Q

The following statements are valid for serotonin:

a) Its the main product of tryptophan catabolism
b) serotonin is 5-hydroxy-tryptamine
c) it needs tetrahydrobiopterine for synthesis
d) it needs tetrahydrofolate for synthesis
e) it plays a role in the regulation of sleep

A

a, b, c, e

62
Q

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

a) By an active transport mechanism
b) At high ion concentrations the throughput rates become 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

A

D*

63
Q

Which of the following are characteristic for the ER?

a) SERCA
b) PMCA
c) IP3 receptor
d) Ryanodine receptor
e) Na/Ca exchange

A

a, c, d*

64
Q

What is true for the IP3 receptor?

a) Localized both in the plasma mem. and the ER
b) It is a Ca-channel
c) It has 4 Ca binding sites
d) It binds ATP
e) It is activated by phospholipase C

A

b, c, d*

65
Q

What are the molecular effects of digitalis - like compounds?

a) Stimulation of sodium potassium ATPase endocytosis
b) Inhibition of endocytosed membrane traffic
c) Activation of signal transduction mechanisms
d) Activation of calcium oscillations in the cytoplasm
e) Indirect activation of the plasmalemmal sodium/calcium exchanger

A

a, d, e

Biochemistry (9 decks)

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