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Biochem 2 > Lecturio - Urea Cycle > Flashcards

Lecturio - Urea Cycle Flashcards

1
Q

Nitrogen is needed for synthesis of ___

A

1/ Nucleotides (ATP, GTP, CTP, UTP, dATP, dCTP, dGTP, dTTP)
2/ Non protein AAs (Ornithine, Citrulline, Sarcosine)
3/ Other nitrogen-containing compounds (choline, carnitine, and vitamins)

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2
Q

Solubility of ammonia. Why?

A

1 nitrogen, water soluble and toxic

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3
Q

Solubility of urea. Why?

A

2 nitrogens, very water soluble

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4
Q

Solubility of uric acid. Why?

A

4 nitrogens, not very water soluble

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5
Q

Uric acid is produced by ____

A

purine catabolism

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6
Q

Urea is produced by ____

A

urea cycle

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7
Q

The Central Role of Glutamate
-> Identify

A

Glutamic acid

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8
Q

The Central Role of Glutamate
-> Identify

A

α-ketoglutaric acid

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9
Q

The Central Role of Glutamate
-> Identify

A

1/ Glutamine synthetase
2/ Glutamine transaminase

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10
Q

The Central Role of Glutamate
-> Identify

A

Glucose-alanine cycle

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11
Q

Location of urea cycle?

A

Primarily occurs in liver; also in kidney

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12
Q

What does urea cycle contain?

A

Consists of 4 cycle reactions and 1 feeder reaction

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13
Q

What does urea cycle contain?

A

Consists of 4 cycle reactions and 1 feeder reaction

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14
Q

The role of Feeder reaction in Urea Cycle?

A

It incorporates 1 molecule of ammonia and 1 CO2 per turn.

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15
Q

The role of Cycle reaction in Urea Cycle?

A

It provides 1 amine from an amino acid.

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16
Q

Output of Urea cycle is ____ per turn

A

1 molecule of urea

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17
Q

The net reaction per turn of the UREA cycle is:

A

2NH3 +CO2 +3ATP+H2O -> urea + 2ADP + 4Pi +AMP

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18
Q

urea cycle
-> Identify

A

NH4+ + HCO3-

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19
Q

Urea Cycle
-> Identify

A

Urea

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20
Q

Urea Cycle
-> Identify

A

1/ Carbamoyl phosphate synthetase
2/ Ornithine Transcarbamoylase
3/ Argininosuccinate Synthetase
4/ Argininosuccinate Lyase
5/ Arginase

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21
Q

What is the source of ammonium ion in urea cycle?

A

The source of ammonium ion is glutamine or glutamate

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22
Q

The source of ammonium ion is glutamine or glutamate.
=> The reaction require which enzyme(s)?

A

The reaction requires action of glutaminase (glutamine) or glutamate dehydrogenase (glutamate).

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23
Q

Carbamoyl Phosphate Synthetase Reaction
-> What is the net reaction?

A

2 ATP + HCO3 + NH4+ <=> 2 ADP + carbamoyl phosphate + P

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24
Q

Carbamoyl Phosphate Synthetase Reaction
-> Identify

A
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25
Q

Identify these molecules

A
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26
Q

Identify the enzyme for this reaction

A

Ornithine transcarbamoylase

27
Q

Ornithine Transcarbamoylase Reaction
-> Ornithine Transcarbamoylase is expressed only in ___

A

liver

28
Q

Ornithine Transcarbamoylase Reaction
-> What is the inheritance pattern of this enzyme?

A

X-linked

29
Q

Ornithine Transcarbamoylase Reaction
-> What are the most common treatments for the deficiency of Ornithine Transcarbamoylase?

A

1/ Low protein diet
2/ Liver transplant

30
Q

In urea cycle, which enzyme is the most commonly deficient enzyme?

A

Ornithine transcarbamoylase

31
Q

What is the alternative way to produce Citrulline? (except using Ornithine transcarbamoylase)

A

By using Nitric oxide synthase

32
Q

How is nitric oxide synthetase used to produce citrulline

A
33
Q

Alternate means of producing citrulline nitric oxide synthase
-> What is the substrate for reaction?

A

Arginine

34
Q

Citrulline movement to cytoplasm requires ____

A

ornithine-citrulline translocase

35
Q

Citrulline movement to cytoplasm requires ornithine-citrulline translocase
-> Characteristics of this transporter

A

Antiport moves citrulline out, ornithine in
-> Needed for both parts of urea cycle (mitochondrial and cytosol)

36
Q

Citrulline movement to cytoplasm requires ____

A

ornithine-citrulline translocase

37
Q

Identify

A

1/ Citrulline
2/ Ornithine

38
Q

What are the 2 step reaction of Argininosuccinate Synthetase?

A
  • First, AMP attaches to amine-rich end of citrulline
  • Next, aspartate displaces the AMP
39
Q

Argininosuccinate Synthetase
-> What is happening at 1?

A

First, AMP attaches to amine-rich end of citrulline

40
Q

Argininosuccinate Synthetase
-> What is happening at 2?

A

aspartate displaces the AMP

(Two step reaction
* First, AMP attaches to amine-rich end of citrulline
* Next, aspartate displaces the AMP)

41
Q

What is the product of Argininosuccinate Synthetase?

A

The product is L-argininosuccinate.

42
Q

Which reaction in urea cycle is the rate-limiting step?

A

Reaction catalyzed by Argininosuccinate Synthetase

43
Q

Argininosuccinate Synthetase
-> Gene expression of enzyme reduced by (1)____, increased by (2)____

A

1/ arginine
2/ citrulline

44
Q

Argininosuccinate Synthetase defects lead to ____

A

citrullinemia - accumulation of ammonia

45
Q

Argininosuccinate Synthetase defects lead to citrullinemia - accumulation of ammonia
-> What are the most common treatments?

A

Treated with low protein diet, arginine supplementation

46
Q

Argininosuccinate Lyase important for production of ____

A

arginine

47
Q

Argininosuccinate Lyase reaction
-> Identify

A

1/ Argininosuccinic acid
2/ Arginine
3/ Fumaric acid

48
Q

Identify the enzyme catalyzed this reaction

A

Arginosuccinate lyase

49
Q

In Urea Cycle, which reaction is the source of fumarate?

A

Reaction catalyzed by Argininosuccinate Lyase

50
Q

UREA CYCLE
In Argininosuccinate Lyase reaction, what is the fate of arginine?

A

To proteins or remainder of urea cycle

51
Q

UREA CYCLE
In Argininosuccinate Lyase reaction, what is the fate of fumarate?

A

To citric acid cycle

52
Q

Identify these molecules

A

1/ Arginine
2/ Urea
3/ Ornithine

53
Q

Identify the enzyme

A

Arginase

54
Q

Arginase is co-expressed with ____

A

nitric oxide synthase in smooth muscle

55
Q

Arginase
-> Increased arginase activity reduces____

A

nitric oxide production.

56
Q

Arginase
-> The role of Nitric oxide

A

Nitric oxide relaxes smooth muscle and facilitates erection of penis.

57
Q

In urea cycle, what is the fate of urea?

A

Excretion

58
Q

In urea cycle, what is the fate of Ornithine?

A

To mitochondria to complete cycle through Ornithine citrulline translocase

59
Q

Carbamoyl phosphate synthetase I deficiency
-> Accumulating molecules?

A

Ammonia

60
Q

Ornithine transcarbamylase deficiency
-> Accumulating molecules?

A

Ornithine, uracil, orotic acid

61
Q

Citrullinemia
-> Enzyme deficiency? Accumulating molecules?

A

Enzyme - Argininosuccinate synthetase
Accumulating molecules - Citrulline

62
Q

Argininosuccinic aciduria
-> Enzyme deficiency? Accumulating molecules?

A

Enzyme - Argininosuccinate lyase
Accumulating molecules - Citrulline, arginiosuccinic acid

63
Q

Argininemia
-> Enzyme deficiency? Accumulating molecules?

A

Enzyme - Arginase
Accumulating molecules - Arginine

Biochem 2 (38 decks)

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