Amino Acid Metabolism EC Flashcards

1
Q

Nitrogen containing substances are used in the synthesis of what compounds?

A
Nucleotides
Neurotransmitters
Hormones
Porphyrins
Nonessential amino acids
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2
Q

What are the essential amino acids?

A
Phenylalanine
Valine
Tryptophan
Threonine
Isoleucine
Methionine
Histidine
Leucine
Lysine
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3
Q

Which amino acids are acidic?

A

Aspartate

Glutamate

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4
Q

Tremor, slurred speech, somnolence, vomiting, cerebral edema, and blurred vision

A

Ammonia intoxication
Liver disease or urea cycle enzyme deficiency
NH4 accumulates and depletes a-ketoglutarate (blocks TCA)

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5
Q

What happens to carbon skeletons of amino acids after the ammonia has been removed?

A

They are degraded and become intermediates in the TCA cycle

Some are ketogenic: Lysine & Leucine
Some are both: Isoleucine, Phenylalanine, Typrtophan, & Tyrosine
Some are glucogenic: rest

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6
Q

Tyrosine derivatives

A

Thyroid hormones

DOPA (dopamine, NE/Epi, melanin)

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7
Q

Methionine

A

S-Adenosylmethionine (SAM) - methyl group transfers
Homocysteine
Cysteine

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8
Q

Tryptophan

A

Niacin
Serotonin
Melatonin

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9
Q

Glutamate

A

GABA

Glutathione

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10
Q

Glycine

A

Porphyrin (heme)

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11
Q

Arginine

A

Creatine
NO
Urea

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12
Q

Histidine

A

Histamine

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13
Q

Phenylalanine

A

Tyrosine (dopa, thyroid hormones)

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14
Q

What does phenylalanine hydroxylase do?

A

Convert Phenylalanine to Tyrosine

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15
Q

Man presents with knee and back pain. Dark spots on conjunctiva and nasal bridge. Urine turns dark if forgets to flush.

A

Alkaptonuria
Defective homogentisic acid oxidase (degrades tyrosine)
Tyrosine, Phenylalanine, and Homogentisic acid build up

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16
Q

Presents to ER with sudden severe, intermittent right flank pain w/ n/v. Urinalysis shows hematuria. Kidney stones with cysteine crystals found.

A

Cystinuria
Defective transport of Cysteine, Ornithine, Arginine, & Lysine “COAL”

Cystosis - intralysosomal accumulation of cysteine

17
Q

Fanconi Syndrome

A

Renal proximal tubule dysfunction (hypophosphatemia, glycosuria, amino aciduria, hypokalemia)

Growth retardation, rickets, polyuria, dehydration, metabolic acidosis, photophobia.

18
Q

Man complaining of photosensitive rash on face and neck and extensor surfaces. Has been feeling more irritable than normal and is somewhat ataxic. Eats healthy with a well balanced diet.

A

Hartnup disease
Mutation in neutral a.a. transporter
Tryptophan excreted in urine and not absorbed in gut
Leads to niacin deficiency-pellagra

19
Q

7 yo boy presents complaining of diminished visual acuity. On p/e, lenticular dislocation found along with abnormally long fingers. Has mild mental retardation. Labs reveal elevated serum methionine and urine homocysteine.

A

Homocystinuria

Defects: 
Cystathionine synthase (or PP/B6 cofactor affinity). Homocysteine methyltransferase

Homocysteine accumulates-
toxic to vascular endothelium (atherosclerosis),
interferes with collagen formation (ocular/skeletal)

20
Q

4 day old infant presents because vomiting and urine smells sweet. Moro reflex absent and rigid. Labs show metabolic acidosis.

A

Maple Syrup Urine Disease
Defect in BCKD (branched chain ketoacid dehydrogenase)
Diminished breakdown of Isoleucine, Leucine, & Valine
“I Love Vermont Maple Syrup”

Ketoacids toxic to brain
Branched chain a.a.’s in urine lead to sweet smell

21
Q

2 y/o blonde haired blue eyes immigrant presents with possible developmental delays. Hypertonia and hyperreflexia and smells “musky”. Guthrie test positive, phenylketones in urine.

A

PKU (phenylketonuria)
Defect in Phenylalanine Hydroxylase or tetrahydrobiopterin cofactor (converts phenylalanine to tyrosine)
Phenylalanine buildup causes brain damage (and becomes deficient in tyrosine derivatives)
Avoid foods w/ phenylalanine (aspartame)