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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
Due to enzyme defects in the urea cycle
Hereditary Hyperammonemia
26
Most common hereditary hyperammonemia
Ornithine transcarbomylase deficiency
27
Most severe hereditary hyperammonemia
Carbamoyl phosphate synthetase I deficiency
28
Characterized by hyperammonemia, elevated blood glutamine, decreased BUN, and respiratory alkalosis
Hereditary Hyperammonemia
29
Seen in adults with compromised liver function | Due to cirrhosis
Acquired Hyperammonemia
30
Purely Ketogenic
Lysine | Leucine
31
Glucogenic and Ketogenic
Phenylalanine Tyrosine Isoleucine Tryptophan
32
Phenylketonuria: Characteristic odor to urine
Phenylacetate
33
Treatment of Phenylketonuria
Dietary control to decrease phenylalanine and increased tyrosine
34
Congenital deficiency of homogentisate oxidase in the degradative pathway of tyrosine, leading to build up of homogentisic acid
Alkaptonuria
35
_________ cause urine to turn black
Alkapton bodies
36
Ochronosis
Alkaptonuria
37
Defective melanin synthesis from tyrosine Absence of pigment from hair, eyes, skin Increased risk for skin cancer
Albinism
38
Defect in methionine degradation leads to: High plasma and urinary levels of homocysteine and methionine Low levels of cysteine
Homocystinuria
39
Clinical Presentation of Homocystinura
Ectopia lentis MI Stroke in children and young adults
40
Treatment for Homocystinuria
Restriction of methionine | Supplementation with vitamins B6, B12, and folate
41
Inherited defect of renal tubular amino acid transporter for Cystine, Ornithine, Lysine and Arginine in the PCT of the kidneys
Cystinuria
42
Excess cystine in urine can lead to precipitation of cystine kidney stones and cause staghorn calculi
Cystinuria
43
Treatment of Cystinuria
Acetazolamide to alkalinize the urine
44
Defect in the conversion of methylmalonyl CoA to succinyl CoA
Methylmalonyl CoA Mutase Deficiency
45
Stroke at the age of 1 month to 1 year
Methylmalonyl CoA Mutase Deficiency
46
Deficiency in a-ketoacid dehydrogenase
MSUD
47
MSUD: a-ketoacids accumulate in the blood, especially
Leucine
48
Characteristic odor imparted to the urine by the
a-keto acids
49
Cyclic compounds by the linkage of four pyrole rings through methyne bridges
Porphyrins
50
Steps in Heme Synthesis
1. Formation of d-aminolevulinic acid 2. Formation of porphobilinogen 3. Formation of uroporphyrinogen 4. Formation of heme
51
Identify the enzyme: Glycine + Succinyl CoA -> d-Aminolevulinic acid
ALA synthase
52
Co-factor ALA synthase
Pyridoxine
53
Biliverdin color
Green
54
Bilirubin color
Red orange
55
Identify the enzyme: Formation of Bilirubin
Heme oxygenase system of reticuloendothelial cells
56
Bilirubin transported to the liver in the blood by binding to
Albumin
57
In the liver, bilirubin binds to intracellular proteins, particulary to
Ligandin
58
Identify the enzyme: Formation of Bilirubin diglucoronide
Bilirubin glucuronyltransferase
59
Deficient in formation of bilirubin diglucoronide leads to
Crigler-Najjar I and II | Gilbert Syndrome
60
Bilirubin -> Urobilinogen
Colorless
61
Urobilinogen -> Stercolin
Brown
62
Remaining urobilinogen converted to urobilin
Yellow
63
Lead inactivates many enzymes in heme synthesis
ALA dehydratase and ferrochelatase
64
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
Porphyrias
65
Most common porphyrias
Porphyria cutanea tarda
66
Results from an elevatd level of plasma bilirubin
Jaundice
67
Used to measure bilirubin in serum
Van den Bergh reaction
68
Assay with no methanol measures
Direct bilirubin
69
Assay with methanol measures
Total bilirubin
70
Difference between the two measures is
Indirect bilirubin

Biochemistry (10 decks)

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