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unit 6: MCP > AA metabolism (14) > Flashcards

AA metabolism (14) Flashcards

1
Q

What are two pathological conditions that can cause ammonia toxicity?

A
  1. liver failure

2. metabolic diseases

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2
Q

What are the symptoms of ammonia toxicity?

A

irritability, vomiting, lethargy and confusion, respiratory distress, migraines

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3
Q

What does ketogenic mean?

A

amino acids are degraded to either acetyl coenzyme A or acetoacetyl coA

-these give rise to ketone bodies

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4
Q

Which amino acids are ketogenic?

A

leucine and lysine

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5
Q

What does glucogenic mean?

A

Amino acids that are degraded to pyruvate or CAC intermediates

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6
Q

How are the levels of glutamate, GABA, serotonin affected in ammonia toxicity

A

GABA and glutamate - decreased

Tryptophan - increased

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7
Q

What three amino acids are converted directly to pyruvate?

A
  1. Alanine
  2. serine
  3. cysteine
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8
Q

What enzyme converts alanine to pyruvate and what is the reaction type?

A

alanine transaminase - ALT
transamination of alpha-ketoglutarate

-important for liver function tests!

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9
Q

What is glycine converted into? What enzymes?

A

serine –> pyruvate
-serine hydroxymethyltransferase

or

into CO2 and free ammonia
-glycine cleavage enzyme

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10
Q

What cofactor does serine hydroxymethyltransferase use? What happens to the cofactor during the breakdown of glycine?

A

THF —> 5,10 methylene-THF

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11
Q

Why is the glycine –> serine –> pyruvate conversion reaction so important?

A

major source of one carbon groups in the body

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12
Q

What is threonine converted into?

A

to glycine –> serine –> pyruvate

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13
Q

Is the threonine breakdown reaction reversible or irreversible?

A

irreversible - duhh its an essential AA

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14
Q

What AAs are broken down into OAA?

A

Aspartate and aspargine

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15
Q

What enzyme breaks down aspartate ?

A

aspartate transaminase - AST

another marker for liver damage

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16
Q

Which AAs are converted to glutamate? how many carbons do these AAs have?

A

5 carbon AAs:

  1. arginine
  2. histidine
  3. proline
  4. glutamine
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17
Q

Which of these amino acids uses THF as a cofactor in it’s breakdown reaction: histidine, arginine, proline, glutamine?

A

histidine

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18
Q

Which amino acid is only essential during growth?

A

arginine

- need extra since the liver is constantly breaking it down to orthinine and urea

19
Q

What amino acids are considered branched chain amino acids? what enzyme do these use for breakdown?

A
  1. valine
  2. leucine
  3. isoleucine

branched chain AA transaminase

20
Q

What happens in mice that have branched chain AA trasaminase deficiency ?

A
  • inc insulin sensitivity
  • inc protein turnover
  • inc serum leucine levels
  • dec fat and body weight
  • inc E expenditure
  • looking into it as a weight loss product
21
Q

BCATs breakdown branched chain AAs into what?

A

alpha-keto acids

22
Q

What enzyme breaks down alpha-keto acids by oxidative decarboxylation? What are it’s cofactors?

A

brached chain ketoacid dehydrogenase

-TPP, Lipoamide, FAD, NAD

23
Q

What is deficient in maple syrup urine disease? What happens as a result?

A

branched chain ketoacid dehydrogenase

-branched chain ketoaciduria

24
Q

What are the treatments for maple syrup urine disease?

A

dietary restriction of branched chain AAs
- some will respond to thiamine!!

(branched chain ketoacid dehydrogenase uses thiamine as a cofactor)

25
Q

Which amino acids are broken down to form succinyl coA?

A
  1. methionine
  2. isoleucine
  3. valine
26
Q

Which amino acids are broken down to form fumarate?

A
  1. asparate
  2. tyrosine
  3. phenylalanine
27
Q

What is formed by the hydroxylation of phenylalanine? What enzyme?

A

tyrosine

-phenylalanine hydroxylase

28
Q

What is the cofactor of phenylalanine hydroxylase?

A

tetrahydrobiopterin (BH4) –>dihydrobiopterin (BH2)

29
Q

Which amino acids are both glucogenic and ketogenic?

A
  1. phenylalanine
  2. isoleucine
  3. tryptophan
  4. tyrosine
  5. threonine
30
Q

What is deficient in PKU? What happens as a result?

A

phenylalanine hydroxylase

-accumulation of toxic derivatives - phenylpyruvate

31
Q

Are infants tested at birth for PKU?

A

yes one of the oldest genetic tests

32
Q

What is the treatment of PKU?

A

phenyalanine restricted diet until at least 16 y/o

33
Q

What is atypical PKU?

A

defect in dihydrobiopterin reductase

  • cant regenerate cofactor
  • no treatment
34
Q

What is alkaptonuria?

A

homgentisate oxidase is deficient
-homogentisate is secreted in the urine-dark urine

deposited in bones and cartilage leading to arthritis
-diagnosed by looking in ear lobes with light

35
Q

What disease can result if a patient is deficient in tryptophan?

A

pellagra

36
Q

What is tryptophan the precursor of?

A

serotonin

37
Q

What is arginine formed from?

A

during the urea cycle from ornithine

ornithine is made from glutamate

38
Q

What is serine formed from? Why is this important?

A

3-phosphoglycerate - intermediate in glycolysis

*major source of 1C groups

39
Q

Is cysteine an essential amino acid?

A

only if methionine is not provided in the diet

40
Q

What is homocyteinuria?

A

cystathione synthase deficiency
-homocysteine spills over into urine

-risk factor for atherosclerosis and mental disabilities

41
Q

What is cysteinthionuria?

A

cystathionase deficiency

-cystathione builds up

42
Q

When is tyrosine an essential amino acid?

A

in patients with PKU

-don’t have phenylalanine in their diet

43
Q

What do herbicides do?

A

block the biosynthesis of essential AAs

44
Q

Which amino acids are glucogenic?

A
  1. alanine
  2. arginine
  3. aspartic acid
  4. asparagine
  5. cysteine
  6. glutamic acid
  7. glutamine
  8. glycine
  9. histidine
  10. methionine
  11. proline
  12. serine
  13. valine

unit 6: MCP (17 decks)

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