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Biochem > Amino Acids and Nitrogen > Flashcards

Amino Acids and Nitrogen Flashcards

1
Q

Essential AAs

A

PVT TIM HALL
Phenylalanine, Valine, Threonine
Tryptophan, Isoleucine, Methionine
Histidine, Leucine, Lysine

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2
Q

Acidic AAs

A

Aspartate and Glutamate

Negatively charged at body pH

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3
Q

Basic AAs

A

Arg, Lys, His

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4
Q

What is the most basic AA

A

Arg

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5
Q

What AAs are required in periods of growth

A

Arg and Histidine

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6
Q

What are arginine and lysine required for

A

Nuclear localization signals

High concentrations in histones

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7
Q

Why are lysine and arginine so basic

A

Extra ammonia group

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8
Q

What AA has no charge at body pH?

A

Histidine

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9
Q

What amino acid is important in catecholamine synthesis

A

Phenylalanine, Tyrosine

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10
Q

What happens if you iodinate tyrosine

A

Thyroxine

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11
Q

How is Dopa made

A

Converted from tyrosine with tyrosine hydroxylase + BH4

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12
Q

What makes melanin

A

Converted from Dopa

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13
Q

What makes dopamine

A

Dopa w/B6 and Dopa decarboxylase

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14
Q

What is dopamine converted to

A

NE, with vitamin C

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15
Q

What converts phenylalanine to tyrosine

A

Phenylalanine hydroxylase and BH4

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16
Q

What inhibits Dopa decarboxylase

A

Carbadopa

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17
Q

What stimulates conversion of NE to Epi?

A

Cortisol

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18
Q

What happens when break dopamine down?

A

Get HVA

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19
Q

What happens when NE broken down

A

VMA

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20
Q

What happens when Epi broken down

A

Metanephrine

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21
Q

What 3 things can you make from arginine?

A
  1. Creatine (can transfer phosphate to ATP)
  2. Urea
  3. NO (requires BH4)
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22
Q

What compounds is tryptophan converted to

A

Niacin and Serotonin

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23
Q

What is required to make niacin from tryptophan

A

B6

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24
Q

What is required to make serotonin from tryptophan

A

BH4 and B6

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25
Q

What essential elements are made from niacin?

A

NAD+ and NADP+

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26
Q

What is the precursor to melatonin

A

Serotonin

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27
Q

What is histidine converted to and what is required

A

Histamine, requires B6

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28
Q

What AA is required to make porphyrin

A

Glycine, with B6

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29
Q

What AA is required to make GABA?

A

Glutamate, with B6

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30
Q

What amino acid derivatives require B6 as a cofactor?

A 
Trp -> Niacin
Trp -> Serotonin
His -> Histamine
Glycine -> Porphyrin
Glutamate -> GABA
31
Q

What are the derivatives of glutamate?

A

GABA (with B6)

Glutathione

32
Q

Where does urea cycle take place

A

Liver

33
Q

Rate limiting step in urea cycle

A

CPS-I

34
Q

Where is CPS-I found

A

Mitochondria

35
Q

What is CPS-II rate limiting enzyme of

A

Pyrimidine synthesis

36
Q

What is ornithine transcarbamylase

A

An enzyme in urea cycle that uses ornithine and carbamoyl phosphate to make citruline

37
Q

OTC deficiency

A

XR
Can’t undergo urea cycle
-> Build up N and ammonia
*Low BUN!

38
Q

What is in excess in OTC deficiency

A

Carbamoyl phosphate

39
Q

What is carbamoyl phosphate converted to in OTC?

A

Orotic acid

40
Q

Symptoms in OTC deficiency

A

Hyperammonemia
Can get this in liver disease too
Slurring of speech, somnolence, vomiting, cerebral edema, blurry vision (=hepatoencephalopathy)

41
Q

Most common urea cycle disorder

A

OTC deficiency

42
Q

How to treat OTC deficiency

A

Decrease N load - eat low protein diet
Phenylbutyrate - binds amino acids like glycine and glutamine and help excrete them
Benzoate
Biotin - can stimulate ornithine transcarbamylase if you have it

43
Q

What amino acid is the precursor of porphyrin and heme

A

Glycine

44
Q

What amino acid is the precursor of nitric oxide

A

Arginine

45
Q

What amino acid is the precursor of GABA

A

Glutamate

46
Q

What amino acid is the precursor of S-adenosyl-methionine

A

Methionine

47
Q

What amino acid is the precursor of creatine?

A

Arginine

48
Q

Compare CPS-1 to CPS-2

A

1: Urea cycle in Mt, N from ammonium
2: Pyrimidine synthesis in Cytosol, N from glutamine

49
Q

What are the two ways to get PKU

A
  1. Deficiency in Phe hydroxylase

2. Deficiency on cofactor - BH4

50
Q

What becomes an essential amino acid in PKU

A

Tyrosine

51
Q

What happens to Phe in PKU

A

Becomes phenylketones

52
Q

What causes neurotoxic effects in PKU

A

Excess Phe (not phenylketones)

53
Q

Why do you have fair skin in PKU?

A

Can’t go through pathway to make melanin

54
Q

How is PKU treated

A 
Avoid phenylalanine: high protein foods, aspartame
Augment tyrosine (essential)
\+/- BH4 (tetrahydrobiopterin)
55
Q

What happens to baby of pregnant mom who has PKU?

A

Microcephaly
Intellectual disability
Growth retardation
Congenital heart defects

56
Q

What is alkaptonuria

A

Ochronosis
Congenital deficiency of “homogentisate oxidase” which is in the degradation of tyrosine to fumarate
AR

57
Q

What happens in alkaptonuria

A

Dark connective tissue, brown sclerae, urine turns black on prolonged exposure to air
Arthralgias - b/c homogentisic acid gets deposited in CT and is toxic to cartilage

58
Q

What causes albinism

A

Tyrosinase (can’t make melanin)

Or, no melanocytes where they are supposed to be

59
Q

What is homocystinuria

A

Excess homocystine by 3 different pathways

60
Q

Clinical manifestations

A 
Homocysteine in urine
Mental retardation
Osteoporosis, tall stature
Kyphosis
Atherosclerosis
Lens subluxation (downward)
61
Q

How to treat homocystinuria if it’s a cystathionine synthase problem

A

Decrease dietary methionine
Increase cysteine in diet (can’t make it)
Incr B12, Folate, B6

62
Q

S-Adenosyl-methionine - why important

A

Transfers methyl units in body

Important for NE-> Epi and for synthesis of phosphocreatinine

63
Q

How is SAM made

A

Methionine + ATP

64
Q

What is needed to regenerate methionine

A

B12 and folate

65
Q

Cystinuria

A

Defect of renal tubular AA for “COLA”

66
Q

What does COLA stand for

A

Cysteine
Ornithine
Lysine
Arginine

67
Q

Sx of cystinuria

A

Cysteine kidney stones

68
Q

How are cysteine kidney stones prevented

A

Acetazolamide - alkalinizes urine

69
Q

MSUD

A

Branched chain a-ketoacid dehydrogenase complex deficiency –> build up of isoleucine, leucine, valine

70
Q

Sx of MSUD

A

Intellectual deficiencies
Severe CNS defects
Death

71
Q

Hartnup disease

A

AR defect of transportier in kidneys and intestines

Deficiency of neutral AAs, especially tryptophan

72
Q

What is the pathophysiology of Hartnup disease

A

No tryptophan -> cant make niacin -> pellagra

73
Q

A patient with PKU - what other dietary modifications besides restricting phenylalanine?

A

Incr tyrosine

Replace BH4

Biochem (10 decks)

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