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BMR 603 Test 1 > Nitrogen Metabolism Part 1 > Flashcards

Nitrogen Metabolism Part 1 Flashcards

1
Q

What is the first step in the Catabolism of amino acids?

A

Separation of the amino group from the carbon skeleton.

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2
Q

Transamination reaction (removing amino group from carbon skeleton) requires what coenzyme?

A

Pyridoxal Phosphate

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3
Q

Acquired hyperammonemia

A

Hepatitis, liver ischemia, hepatotoxins, and cirrhosis.

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4
Q

Hereditary hyperammonemia

A

Genetic deficiencies of any of the five enzymes of the urea cycle.

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5
Q

Role of Alanine aminotransferase?

A

Enzyme that transfers amino group from Alanine to a-ketoglutarate, resulting in pyruvate and Glutamate.

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6
Q

Role of Aspartate aminotransferase?

A

Enzyme that transfers amino group from Aspartate to a-ketoglutarate, resulting in Oxaloacetate and Glutamate.

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7
Q

Role of Pyridoxal phosphate (PLP)

A

Coenzyme of aminotransferases.

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8
Q

Role of Glutamate dehydrogenase?

A

Enzyme that drives Oxidative Deamination

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9
Q

What electron acceptors are used for Oxidative deamination?

A

NAD+ or NADP+

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10
Q

Explain the regulation of Glutamate dehydrogenase activity?

A
  • Allosterically regulated:
    • ADP and GDP increase activity
    • ATP and GTP decrease activity.
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11
Q

Ketogenic Amino Acids (7)

A
  • Form Acetyl-CoA:
    • Leu, Ile, Thr, Lys, Phe, Tyr, Trp
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12
Q

Amino acids that can form either Ketogenic or Glucogenic Amino Acids?

A

Ile, Thr, Phe, Tyr, Trp

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13
Q

Glucogenic Amino Acids:

Which AA make pyruvate?

A

Ala, Cys, Gly, Ser, Thr, Trp

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14
Q

Glucogenic Amino Acids:

Which AA make a-ketoglutarate

A

Arg, Glu, Gln, His, Pro

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15
Q

Glucogenic Amino Acids:

Which AA make succinyl-CoA

A

Ile, Met, Thr, Val

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16
Q

Glucogenic Amino Acids:

Which AA make Fumarate?

A

Phe, Tyr

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17
Q

Glucogenic Amino Acids:

Which AA make Oxaloacetate

A

Asp, Asn

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18
Q

Where are branched amino acids metabolized?

A

Peripheral tissues (particularly muscle).

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19
Q

Describe the glutamate pathway?

A
  • ATP and ammonia combine with glutamate to make glutamine.
    • Uses Glutamine synthetase
  • Travel to liver, and the process is reveresed.
20
Q

Describe the glucose-alanine cycle?

A
  • Glutamate is made by transamination, by transfering amino group to pyruvate.
    • Done by alanine aminotransferase.
  • Pyruvate is changed to alanine and sent to ther liver.
  • Alanine then undergoes transamination and becomes pyruvate which is turned to glucose and shipped back to muscle.
21
Q

What is the first nitrogen-acquiring reaction of the Urea cycle and what is the enzyme used?

A
  1. ATP + Bicarbonate —> Carbamoyl Phosphatase
    1. Carbamoyl phosphate synthetase 1
22
Q

Regulation of CPS1

A
  • Requires allosteric activation by N-acetylglutamate.
    • The activator is synthed from Acetyl CoA and Glutamate, both increase after protein rich meal.
23
Q

What role does Ornithine transcarbamoylase have in the urea cycle?

A
  • Combines Ornithine and Carbamoyl phosphate into Citrulline.
24
Q

What is the second nitrogen-acquireing reaction of the Urea Cycle?

A
  • In Cytosol: Citrulline + ATP —> Argininosuccinate
    • Argininosuccinate synthetase.
25
Q

What is the fourth step of the Urea cycle?

A
  • Argininosuccinate —-> Arginine + Fumarate
    • Argininosuccinate Lyase: Cleaves a fumarate group off.
26
Q

What is the final step in the Urea Cycle?

A
  • Arginine + H2O —-> Ornithine + Urea
    • Arginase
27
Q

What are the net effects of the urea cycle?

A
  • Eliminated nitrogen from ammonia and aspartate, as well as part of a CO2.
  • Cycle regenerates Ornithine to use again.
28
Q

How many high energy phosphate bonds are used per molecule of urea?

A

4

29
Q

What two molecules link the Urea Cycle to the TCA cycle? and how?

A
  • Aspartate and Fumarate.
  • Aspartate (TCA) combines with Citrulline (Urea) to make Argininosuccinate.
  • Argininosuccinate is then split into Arginine (Urea) and Fumarate (TCA)
30
Q

What is Tertrahydrobiopterin

A

The oxidation of Phe by phenylalanine hydroxylase.

31
Q

What does N5-methyl THF do and why is it notable?

A

It regenerates S-adenosylmethionine (adoMet).

This is its only known use in mammals

32
Q

How is adoMet synthesized?

A

ATP and Methionine

33
Q

How is Tetrahydrofolate formed?

A

From Folate

34
Q

What is special about THF (Tetrahydrofolate)

A
  • Can transfer 1-carbon in different oxidative states
    • Example: CH3, CH2OH, and CHO
35
Q

Catabolic pathway for Asparagine > Aspartate > Oxaloacetate

A
  1. Asparagine
    1. Asparaginase
  2. Aspartate
    1. Aspartate aminotransferase
  3. Oxaloacetate
36
Q

Disorder involving Degradation of branched chain amino acids

A

Maple Syrup Urine

37
Q

What causes metabolic defects in amino acid metabolism?

A
  • Enzyme deficiencies
  • Build up of products and result in severe health effects.
  • Managed by restricting intake.
38
Q

What disorder is caused by an issue in Phe degradation to Tyr?

A

Phenylketonuria

39
Q

What are the symptoms of PKU (Phenylketouria) and what causes it.

A
  1. Issue in first step of Phe dehydrogenation to Tyr
  2. Elevated phenylalanine
    1. CNS symptoms
    2. Hypopigmentation
40
Q

What disorder is caused by an issue in oxidase that breaks open Homogentisate (during catabolism of Tyr).

Symptoms?

A

Alkaptonura

Benignl; urine contains elevated levels of homogentisic acid, making it black.

41
Q

What causes Albinism?

A

Defective Melanin synthesis from tyrosine.

Enzyme responsible: Tyrosine 3-monooxygenase (Tyrosinase)

42
Q

What enzyme fails for Homocystinuria?

A

Cystathionine synthase

43
Q

Symptoms of Homocystinuria?

A

High plasma and urinary levels of Homocysteine and methionine.

Eye, skeletal, and arterial abnormalities, retardation.

44
Q

Degradation and Resynthesis of methionine.

A

Can go two paths once it is at L-Homocysteine.

  • If B6 is present L-Cysteine will ultimately be formed
  • If N5-Methyltetrahydrofolate and B12 are present L-Methionine and Tetrahydrofolate will form
45
Q
A

BMR 603 Test 1 (10 decks)

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