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Dems Unit 02 - 02 > AA - Degradation and synthesis 20 > Flashcards

AA - Degradation and synthesis 20 Flashcards

1
Q

Which two aa are nonessential and can be synthesized from essential aa?

A

cysteine

tyrosine

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2
Q

AA that are glucogenic AND ketogenic

A

Nonessential:
- tyrosine

Essential:

  • Isoleucine
  • phenylalanine
  • tryptophan
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3
Q

AA that are ketogenic

A

Essential:

  • Leucine
  • Lysine
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4
Q

Catabolism of Ketogenic AAs yield . . .

A

aa whos catabolism yields either:
acetoacetate
or its precursors ( acetyl coA/acetoacetyl coA)

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5
Q

AAs that form oxaloacetate and how

A

asparagine –> aspartate + NH3 via asparaginase

Aspartate –> oxaloacetate + glutamate via aminotransferase (transamination)

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6
Q

Glutamate can be transaminated or oxidatively deaminated and converted to a-ketoglutarate. Which AAs can form glutamate, and ultimately a-ketoglutarate?

A
  1. Glutamine
  2. Proline
  3. Arginine
  4. Histidine

Gln, Pro, Arg, His
Q, P, R, H

pg 262

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7
Q

AA that form Pyruvate

A
  1. Alanine
  2. Cystine
  3. Glycine
  4. Serine
  5. Threonine
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8
Q

Major gluconeogenic AA

A

ALanine –> pyruvate

- loses its aa by reversible transamination to form pyruvate

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9
Q

AA that form fumarate

A

Phenylalanine
Tyrosine
(both are glucogenic + ketogenic)

Phe gets converted to Tyr via phenylalanine hydroxylase

Tyr can then form fumarate + acetoacetate

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10
Q

There is a relationship with homocysteine to what types of diseases?

A

vascular

  • elevated lvls promote oxidative damage
  • inflammation
  • endothelial dysfxn
  • occlusive vascular disease
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11
Q

Plasma homocysteine levels are inversely associated with high lvls of what 3 vitamins?

A

Folate
B6
B12

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12
Q

Pregnant women are given folate to prevent what?

A

NTD
- Folate is inversely related to homocysteine levels
Low homocysteine levels help prevent NTD

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13
Q

Branched chain aa are unique in that they are metabolized primarily by?

A

peripheral tissue (muscle) rather than by the liver

- leucine
- isoleucine
- valine
all are essential

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14
Q

Active form of folate and its use

- what does a deficiency in folate result in?

A

Tetrahydrofolic acid (THF)

  • Made from folate + 2 NADPH
  • allows one carbon compounds to be recognized and manipulated by biosynthetic compounds.
  • Deficiency presents as megaloblastic anemia
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15
Q

Here are 3 AAs, list their corresponding a-keto acids
alanine
aspartate
glutamate

A

alanine- pyruvate
aspartate - oxaloacetate
glutamate - a-ketoglutarate

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16
Q

PKU

  • cause
  • characteristics of classic PKU
  • tx
A

caused by a deficiency of phenylalanine hydroxylase (PAH)
(pg 269 cant convert Phe to Tyr)
- accumulation of Phe
- deficiency in Tyr (Tyr bcomes essential acid in PKU)

  1. Elevated Phe
    - urine has a “mousey” odor
  2. CNS sx
    - mental retardation, cant walk/talk, seizure, hyperactivity, tremor, microcephaly, failure to grow
  3. Hypopigmentation
    - fair hair, light skin, blue eyes
    - Hydroxylation of Tyr is first step in forming melanin

Tx: dietary - ingest nec. protein w low Phe levels
- Phe is essential aa - need it in diet

17
Q

Dihydropteridine reductate deficiency

A

Dihydropteridine reductase Regenerates BH4 from BH2

  • BH4 is needed for Phe hydroxylase, Tyr hydroxylase, Try hydroxylase
  • can result in Hyperphenylalaninemia
18
Q

Maple syrup urine disease (MSUD)

  • cause
  • characteristics of classic PKU
  • tx
A

partial or complete deficiency in branched chain a-keto acid dehydrogenase

  • Leu, Iso, Val cannot be decarboxylated + accumulate in blood
  • infants show sx in first few days of life (can be lethal!)
  1. Feeding problems:
    - vomiting, dehydration
  2. Severe met acidosis
  3. Maple syrup odor to the urine

Tx: synthetic formula that contains limited amts of leu, iso, val. Just sufficient to grow + develop

*note: branched chain aa are imp E source in times of metabolic need, and indiv with MSUD are at risk for decompensation during periods of increased protein catabolism

19
Q

Albinism

A

defect in Tyr metabolism –> deficiency in production of melanin
- increased risk of skin cancer

20
Q

Homocystinuria

  • cause
  • characteristics of classic PKU
  • tx
A

group of disorders involving defects in metabolism of homocysteine.
- high lvl homocysteine + methionine
- low lvl cysteine
- most common: defect in cystathionine B synthase
(converts homocysteine to cystathionine)

  1. ectopia lens (displace lens of eye)
  2. skeletal abnormalities
  3. thrombi prone
  4. osteoporosis
  5. neuro deficits

tx: restriction of methionine intake and supplementation with Vit folate, B6, B12

21
Q

Clinically imp aa:
Methionine
Arginine
Glutamine

A

Methionine

  • source of methyl groups in met.
  • precursor of cysteine

Arginine

  • Member of urea cycle
  • precursor of NO

Glutamine

  • storage and transport form of ammonia
  • precursor of purines an pyrimidines
22
Q 
Clinically imp aa:
Phe
His
Tryp
Ala
A

Phe

  • precursor to tyrosine
  • elevated in PKU

His

  • precursor to histamine
  • elevated in histidinemia

Tryp
- precursor to serotonin

Ala

  • transport form of ammonia from muscle
  • key glucogenic aa

Dems Unit 02 - 02 (20 decks)

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