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Biochemistry > Nitrogen Metabolism > Flashcards

Nitrogen Metabolism Flashcards

1
Q

Net accumulation of proteins as in growth and pregnancy

A

Positive Nitrogen Balance

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2
Q

Net breakdown of protein as in surgery, advanced cancer, kwashiorkor or marasmus, starvation

A

Negative Nitrogen Balance

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3
Q

Sum of all free amino acids in cells and extracellular fluid

A

Amino Acid Pool

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4
Q

Removal of the a-amino group forming ammonia

A

First Phase of Amino Acid Catabolism

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5
Q

Deamination means

A

Removal of the a-amino group to form ammonia

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6
Q

Carbon skeletons of a-ketoacids are converted to Glycolysis/Krebs Cycle

A

Second Phase of Amino Acid Catabolism

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7
Q

Excretion of Excess Nitrogen: Seen in telostean fish, which excrete highly toxic ammonia

A

Ammonitelic

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8
Q

Excretion of Excess Nitrogen: Uricotelic

A

Seen in birds, which excrete uric acid as semisolid guano

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9
Q

Excretion of Excess Nitrogen: Seen in land animals and humans, who excrete non-toxic, water soluble area

A

Ureotelic

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10
Q

Steps of First Phase of Amino Acid Catabolism

A

Step 1: Transamination

Step 2: Oxidative Deamination

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11
Q

Amino acids transfer their a-amino group to a-ketoglutarate, resulting in the formation of ________

A

Glutamate

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12
Q

Identify the enzyme: a-ketoglutarate -> glutamate

A

Aminotransferase

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13
Q

Coenzyme of aminotransfrase

A

Pyridoxal phosphate

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14
Q

Identify the enzyme: Glutamate is oxidatively deaminated to release free ammonia

A

Glutamate dehydrognase

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15
Q

Transport of Ammnonia from Peripheral Tissues

A

Through Glutamine

Through Alanine

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16
Q

In most tissues, glutamate combines with ammonia to form glutamine via

A

Glutamine synthetase

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17
Q

Glutamine is transported in the blood and may be deaminated to release ammonia in two organs:

A

Liver: in response to high protein intake
Kidneys: in response to metabolic acidosis

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18
Q

Conversion of the body’s nitrogenous waste to urea

A

Urea Cycle

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19
Q

Where does Urea Cycle occur

A

Liver only

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20
Q

What are the substrates of Urea Cycle

A

NH3
Aspartate
CO2

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21
Q

What is the product of Urea Cycle

A

Urea

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22
Q

Rate limiting step of Urea Cycle

A

Carbamoyl phosphate synthetase I

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23
Q

Allosteric Activator of Carbamoyl phosphate synthetase I

A

N-acetylglutamate

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24
Q

Has a direct neurotoxic effect on the central nervous system

A

Hyperammonemia

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25
Q

Due to enzyme defects in the urea cycle

A

Hereditary Hyperammonemia

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26
Q

Most common hereditary hyperammonemia

A

Ornithine transcarbomylase deficiency

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27
Q

Most severe hereditary hyperammonemia

A

Carbamoyl phosphate synthetase I deficiency

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28
Q

Characterized by hyperammonemia, elevated blood glutamine, decreased BUN, and respiratory alkalosis

A

Hereditary Hyperammonemia

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29
Q

Seen in adults with compromised liver function

Due to cirrhosis

A

Acquired Hyperammonemia

30
Q

Purely Ketogenic

A

Lysine

Leucine

31
Q

Glucogenic and Ketogenic

A

Phenylalanine
Tyrosine
Isoleucine
Tryptophan

32
Q

Phenylketonuria: Characteristic odor to urine

A

Phenylacetate

33
Q

Treatment of Phenylketonuria

A

Dietary control to decrease phenylalanine and increased tyrosine

34
Q

Congenital deficiency of homogentisate oxidase in the degradative pathway of tyrosine, leading to build up of homogentisic acid

A

Alkaptonuria

35
Q

_________ cause urine to turn black

A

Alkapton bodies

36
Q

Ochronosis

A

Alkaptonuria

37
Q

Defective melanin synthesis from tyrosine
Absence of pigment from hair, eyes, skin
Increased risk for skin cancer

A

Albinism

38
Q

Defect in methionine degradation leads to:
High plasma and urinary levels of homocysteine and methionine
Low levels of cysteine

A

Homocystinuria

39
Q

Clinical Presentation of Homocystinura

A

Ectopia lentis
MI
Stroke in children and young adults

40
Q

Treatment for Homocystinuria

A

Restriction of methionine

Supplementation with vitamins B6, B12, and folate

41
Q

Inherited defect of renal tubular amino acid transporter for Cystine, Ornithine, Lysine and Arginine in the PCT of the kidneys

A

Cystinuria

42
Q

Excess cystine in urine can lead to precipitation of cystine kidney stones and cause staghorn calculi

A

Cystinuria

43
Q

Treatment of Cystinuria

A

Acetazolamide to alkalinize the urine

44
Q

Defect in the conversion of methylmalonyl CoA to succinyl CoA

A

Methylmalonyl CoA Mutase Deficiency

45
Q

Stroke at the age of 1 month to 1 year

A

Methylmalonyl CoA Mutase Deficiency

46
Q

Deficiency in a-ketoacid dehydrogenase

A

MSUD

47
Q

MSUD: a-ketoacids accumulate in the blood, especially

A

Leucine

48
Q

Characteristic odor imparted to the urine by the

A

a-keto acids

49
Q

Cyclic compounds by the linkage of four pyrole rings through methyne bridges

A

Porphyrins

50
Q

Steps in Heme Synthesis

A
  1. Formation of d-aminolevulinic acid
  2. Formation of porphobilinogen
  3. Formation of uroporphyrinogen
  4. Formation of heme
51
Q

Identify the enzyme: Glycine + Succinyl CoA -> d-Aminolevulinic acid

A

ALA synthase

52
Q

Co-factor ALA synthase

A

Pyridoxine

53
Q

Biliverdin color

A

Green

54
Q

Bilirubin color

A

Red orange

55
Q

Identify the enzyme: Formation of Bilirubin

A

Heme oxygenase system of reticuloendothelial cells

56
Q

Bilirubin transported to the liver in the blood by binding to

A

Albumin

57
Q

In the liver, bilirubin binds to intracellular proteins, particulary to

A

Ligandin

58
Q

Identify the enzyme: Formation of Bilirubin diglucoronide

A

Bilirubin glucuronyltransferase

59
Q

Deficient in formation of bilirubin diglucoronide leads to

A

Crigler-Najjar I and II

Gilbert Syndrome

60
Q

Bilirubin -> Urobilinogen

A

Colorless

61
Q

Urobilinogen -> Stercolin

A

Brown

62
Q

Remaining urobilinogen converted to urobilin

A

Yellow

63
Q

Lead inactivates many enzymes in heme synthesis

A

ALA dehydratase and ferrochelatase

64
Q

Genetic or acquired disorders due to abnormalities in the pathway of biosynthesis of heme, which result in the accumulation and increased excretion of porphyrins or porphyrin precursors

A

Porphyrias

65
Q

Most common porphyrias

A

Porphyria cutanea tarda

66
Q

Results from an elevatd level of plasma bilirubin

A

Jaundice

67
Q

Used to measure bilirubin in serum

A

Van den Bergh reaction

68
Q

Assay with no methanol measures

A

Direct bilirubin

69
Q

Assay with methanol measures

A

Total bilirubin

70
Q

Difference between the two measures is

A

Indirect bilirubin

Biochemistry (10 decks)

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