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SFM Exam 2 > 12: Protein And AA Metabolism > Flashcards

12: Protein And AA Metabolism Flashcards

1
Q

Three things that supply the AA pool

A
  1. Protein turnover
  2. Digested food
  3. De novo synthesis of non-essential AAs
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2
Q

Three things that deplete the AA pool

A
  1. Body protein production
  2. Synthesis of nitrogenous compounds
  3. Degradation
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3
Q

9 essential AAs

A

H, V
MILK
WTF

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4
Q

Six conditionally essential AAs

A

RPG

CQY

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5
Q

5 non-essential AAs

A

DANSE

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6
Q

Major source of N in the body

A

Dietary protein

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7
Q

Four ways the body excretes N

A
  1. Ammonia
  2. Creatinine
  3. Uric acid
  4. Urobilinogen
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8
Q

In what organ does AA metabolism take place?

A

Liver

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9
Q

What two things form from ketogenic AAs and what two things form from glucogenic AAs?

A

Ketogenic -> acetyl CoA, acetoacetate

Glucogenic -> pyruvate, TCA cycle intermediates

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10
Q

Ketogenic AAs are precursors for what three things?

A

A-keto acids, ketone bodies, FAs

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11
Q

Glucogenic AAs are precursors for what process?

A

Gluconeogenesis

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12
Q

Two ketogenic AAs

A

Leu, Lys

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13
Q

5 AAs that are both ketogenic and glucogenic

A

WIFY T

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14
Q

Release of trypsinogen and chymotrypsinogen

A

Are released into SI lumen as inactive zymogens

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15
Q

What activates trypsinogen?

A

Enteropeptidase (an enterokinase embedded in the intestinal mucosa)

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16
Q

What two things does trypsin activate

A

Chymotrypsinogen + other trypsinogen molecules

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17
Q

Three steps in AA Degradation

A
  1. Aminotransferase
  2. Glutamate dehydrogenase
  3. Urea cycle
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18
Q

Other term for aminotransferase

A

Transaminase

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19
Q

What occurs during a transamination reaction?

A

Amino group of AA is transferred to an a-ketoacid

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20
Q

Coupled reactions of AAs and keto acids

A

All AAs have a conjugate keto-acid; like acid-base reactions

AA + keto acid -> a different AA + keto acid

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21
Q

Required coenzyme for aminotransferase reactions

A

PLP (pyridoxyl-5’-phosphate) (derived from B6)

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22
Q

Two examples of aminotransferases used as markers in medicine

A

Alanine transaminase, aspartate transaminase

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23
Q

What four AAs form glutamate -> which then forms a-ketoglutarate

A

Gln, His, Arg, Pro

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24
Q

Byproduct of glutamine glutamate reactions

A

NH4+

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25
Q

What two enzymes do the glutamine glutamate reactions

A

Glutamate dehydrogenase, glutamine synthase

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26
Q

What cofactor is required in the methionine pathway?

A

PLP

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27
Q

Three branched chain AAs

A

Valine, Leucine, Isoleucine

28
Q

What does phenylalanine hydroxylase do?

A

Turns Phe into Tyr

29
Q

How is ammonia removed from the brain vs other tissues

A

Removed from brain: as Glu or Gln

Removed from other tissues: as Glu

30
Q

How is urea generated?

A

In AA metabolism by deamination mechanisms

31
Q

Goal of urea cycle

A

Produce urea from ammonia

32
Q

What can defects in any of the six urea cycle enzymes cause?

A

Hyperammonemia

33
Q

Example of a urea cycle enzyme

A

NAG synthase

34
Q

Where does the urea cycle occur?

A

Liver mostly, kidneys a little

35
Q

What does ammonia toxicity mostly affect

A

Brain and CNS

36
Q

Toxic agent in ammonia toxicity and why

A

NH3 - it can penetrate membranes

37
Q

Four things formed from tryptophan

A

Serotonin -> melatonin

Niacin -> NADH/NADPH

38
Q

What do serine and glutamate form?

A

Serine: Ach
Glutamate: GABA

39
Q

Four things formed by tyrosine

A
  1. Thyroid hormones
  2. Dopamine -> norep/epi
  3. Melanin
40
Q

Thyroglobulin

A

120 Tyr residues with iodine stuck on them, helps form T3 and T4

41
Q

T3 vs T4

A

T4: 2 diionated Tyr
T3: 1 monoiodonated + 1 diiodinated Tyr

42
Q

Inborn Errors of Metabolism (IEMs)

A

Conditions associated with dysfunctional metabolism of AAs/thier derivatives

43
Q

How many core IEMs are screened, and how many does Missouri screen for?

A

34 core conditions; 59 screened in MO

44
Q

Two things Hartnup disease and Cystinuria have in common

A
  1. Autosomal recessive

2. Associated with defects in AA transporters

45
Q

cause of Hartnup disease

A

Defective transport of non-polar/neutral AAs (ex: Tryptophan)

46
Q

What does Hartnup disease cause?

A

Trp deficiency

47
Q

Clinical associations of Hartnup disease

A

Elevated Trp in urine, failure to thrive, nystagmus, tremor, intermittent ataxia, photosensitivity

48
Q

Cause of cystinuria

A

Defective transport of dimerize cystine and dibasic AAs

49
Q

Four dibasic AAs

A

COAL: cysteine, ornithine, arginine, lysine

50
Q

Clinical associations of cystinuria

A

Formation of cystine crystals in kidney, renal colic

51
Q

What AA is homocysteine most like?

A

Methionine

52
Q

Homocystinuria cause

A

Deficiency in methionine pathway, folate deficiency, or PLP deficiency

53
Q

Four organ systems affected by hyperhomocysteinemia

A

Eyes, skeletal, CNS, vascular

54
Q

Treatment for hyperhomocysteinemia

A

Vitamin supplements can sometimes normalize homocysteine levels

55
Q

What causes maple syrup urine disease

A

Defective BCKD (branched-chain a-keto acid dehydrogenase complex), which causes branched-chain keto-aciduria

56
Q

Clinical associations of maple syrup urine disease

A

Maple syrup urine smell, toxicity in brain (due to branched chain AAs in brain)

57
Q

Treatment of maple syrup urine disease

A

Synthetic diet limiting BCAAs

58
Q

What was the first IEM to be included in newborn screenings?

A

Phenylketonuria

59
Q

What causes phenylketonuria

A

Phenylalanine hydroxylase deficiency: cant form Tyr from Phe

60
Q

Clinical association of phenylketonuria

A

Blocked AA transport in the brain, impaired brain function

61
Q

Treatment of phenylketonuria

A

Limit Phe + use formula containing Tyr

62
Q

Secondary PKU causes what?

A

Tetrahydrobiopterin deficiency (a cofactor of phenylalanine hydroxylase)

63
Q

What causes albinism?

A

Defects in tyrosinase -> conversion of tyrosine to melanin is blocked

64
Q

What is special about orotic aciduria

A

It is an X-linked disease of the urea cycle

65
Q

What enzyme is defective in orotic aciduria

A

Ornithine transcarbamoylase

SFM Exam 2 (19 decks)

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