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BMSC 230 #2 > module 11- amino acid degradation & urea cycle > Flashcards

module 11- amino acid degradation & urea cycle Flashcards

1
Q

what is the 1st step in amino acid degradation

A

nitrogen removal

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2
Q

ammonium ion is converted to what in most terrestrial vertebrates?

A

urea

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3
Q

carbon skeletons of degraded amino acids emerge as?

A

intermediates

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4
Q

T or F: no storage of amino acids so we need them everyday

A

T

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5
Q

inputs to amino acid pool

A

defective cells, dietary protein

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6
Q

T or F: some organisms such as yeast/bacteria can synthesize all 20 amino acids

A

T

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7
Q

average person requires ( ) of dietary protein per day to maintain amino acid pool

A

70-100g

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8
Q

proteolysis- what occurs & where does it begin/end

A

peptide bonds are cleaved, begins in stomach & goes to small intestine

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9
Q

2 purposes of low gastric pH

A

1) causes denaturation of protein
2) antiseptic- destroys bacteria/viruses

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10
Q

2 components of gastric juice

A

pepsin & gastrin

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11
Q

pancreatic juice components

A

bicarbonate & proteases

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12
Q

what does the array of proteases cause?

A

proteins to be rapidly degraded into free amino acids

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13
Q

where are free amino acids absorbed & where do they go

A

endothelial cells, portal vein

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14
Q

all of the proteolytic enzymes involved in protein digestion are synthesized as ( ) to protect from self degradation?

A

inactive zymogens

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15
Q

how are zymogens activated

A

small portion of polypeptide backbone cut off to change conformation

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16
Q

what triggers removal of masking sequence?

A

low pH

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17
Q

autocatalysis

A

self-activation

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18
Q

where are pancreatic proteases stored?

A

granules

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19
Q

protease self-activation

A

attack & degrade each other when their activity is not needed

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20
Q

gastroesophageal reflux disease cause

A

over-active proton pump in the stomach = too much acid production

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21
Q

how do antacids work

A

act as proton sponges & reduce acidity

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22
Q

what pump is involved in GERD

A

K/H pump

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23
Q

inhibition of histamine H2 receptor

A

inhibits histamine = less acid

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24
Q

proton pump inhibitors

A

bind directly to proton pump & inhibit its ability to pump protons into lumen

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25
Q

excess amino groups are secreted in the form of ( ), while carbon skeletons are converted to ( )

A

urea, a-keto acids

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26
Q

what are a-keto acids used for

A

energy production or gluconeogenesis

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27
Q

transamination

A

amino groups form 1 amino acid

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28
Q

oxidative deamination

A

amino group from glutamate is released as NH4

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29
Q

transdeaminination

A

transamination & deamination combined

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30
Q

where does urea production occur

A

liver

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31
Q

what is the 1st step in amino acid degradation

A

transamination

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32
Q

what do aminotransferases do?

A

transfer amino group from a-ketoglutarate to glutamate

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33
Q

what do aminotransferases require as a coenzyme?

A

pyridoxal phosphate- derived from vitamin B6

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34
Q

the nomenclature for aminotransferases are based on?

A

amino acid donor

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35
Q

alaine aminotransferase

A

transfers amino group from alanine to a-ketoglutarate to produce glutamate & pyruvate

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36
Q

aspartate aminotransferase

A

transfers amino group from aspartate to a-ketoglutarate to produce glutamate & oxaloacetate

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37
Q

T or F: elevated aminotransferases levels can be used to diagnose medical conditions

A

T

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38
Q

at pH of 7.4, most is in ( ) form

A

NH4 form

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39
Q

T or F: ammonium is odorless

A

T

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40
Q

glutamate undergoes oxidative deamination which releases ( ) + ( )

A

NH4 + a-ketoglutarate

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41
Q

T or F: we have very little free ammonia in our bodies

A

T

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42
Q

where is free ammonium produced? why?

A

mitochondria, can be used to form urea which prevents accumulation

43
Q

glutamate dehydrogenase

A

removes amino group & oxidation of glutamate

44
Q

electrons removed from glutamate by glutamate dehydrogenase are captured as?

A

NADH or NADPH

45
Q

in most tissues, free ammonium is incorporated into ( ) by ( )

A

glutamine, glutamine synthetase

46
Q

T or F: most amino acids cannot get out of cells

A

T

47
Q

what amino acid can leave cells

A

glutamine

48
Q

glutaminase- location & what does it do

A

liver, uses water to cleave ammonium off of glutamine

49
Q

most ammonim gets transported out of the muscle in the form of?

A

alanine

50
Q

glucose-alanine cycle

A

alanine-> glutamate -> pyruvate -> glucose -> pyruvate

51
Q

contributions to the glutamate pool come from

A

alanine from muscle & glutamine from tissues

52
Q

glutamate is acted on by glutamate dehydrogenase to?

A

releases ammonium

53
Q

urea is ( ) soluble in water

A

highly

54
Q

precursors for urea are?

A

NH4, CO2 & aspartate

55
Q

urea cycle

A

reactions that occur in the mitochondira & the cytosol

56
Q

where does the urea cycle start? why?

A

mitochondria, bc ammonia is released here

57
Q

what is the rate limiting enzyme for urea cycle

A

carbamoyl phosphate synthetase

58
Q

carbamoyl phosphate synthetase I- location

A

mitochondrial matrix

59
Q

obligate allosteric activator of carbomoyl phosphate synthetase I

A

N-acetylglutamate

60
Q

obligate activator

A

required for its target enzyme to have activity

61
Q

how is N-acetylglutamate stimulated

A

presence of arginine

62
Q

where do the 2 amino groups on urea come from?

A

free ammonium & aspartate

63
Q

urea cycle part 2

A

urea is produced & ornithine is replenished

64
Q

citrulline is acted upon by ?

A

argininosuccinate synthetase

65
Q

when argnine is acted upon by the hydrolase arginase, what 2 things are produced?

A

urea & ornithine

66
Q

what 3 enzymes are clustered together in a complex

A

argininosuccinate synthetase, argininosuccinase & arginase

67
Q

what 2 molecules link the urea cycle & the citric acid cycle

A

fumarate & aspartate

68
Q

how is the urea cycle regulated?

A

by N-acetylglutamate & arginine

69
Q

how many ATP are needed per urea molecule formed

A

3

70
Q

ammoniotelic

A

secrete nitrogen as ammonium

71
Q

ureotelic

A

secrete urea

72
Q

how do birds/reptiles ecrete excess nitrogen

A

uric acid

73
Q

hyperammonemia

A

too much ammonium

74
Q

what 2 amino acids can form ammonium

A

serine & theronine

75
Q

acquired vs congential hyperammonemia

A

acquired- liver damage - hepatitis or alcohol

congential- mutation defects

76
Q

glucogenic amino acid & example

A

catabolized to pyruvate or intermediate of CAC

alanine

77
Q

ketogenic amino acid & example

A

catabolized to acetyl CA or acetoacetate

78
Q

what 5 amino acids are ketogenic & glucogenic

A

tryptophan, tyrosine, threonine, phenylalanine, and isoleucine

79
Q

phenylketonuria- what is it, symptoms

A

deficiency in phenylalanine hydroxylase, CNS symptoms

80
Q

maple syrup urine disease- what is it & symptoms

A

deficiency in dehydrogenase complex, CNS symptoms

81
Q

most genetic diseases affecting amino acid catabolism have ( ) effects

A

CNS

82
Q

T or F: genetic diseases affecting amino acid catabolism are very rare

A

T

83
Q

porphyrins

A

cyclic compounds that bind Fe 2+ or Fe 3+

84
Q

all carbon & nitrogen atoms in porphyrins are contributed by ( ) & ( )

A

glycine & succinyl CoA

85
Q

1st step in porphyrins pathway

A

fusion of succinyl CoA & glycine to form ALA

86
Q

porphyrias

A

rare genetic diseases due to defects in porphyrin synthesis & accumulation of intermediates

87
Q

acute intermittent porphyria

A

defect in PBP deaminase

88
Q

how do porphyrin diseases different?

A

accumulation of different intermediates

89
Q

what is most common porphyria?

A

acute

90
Q

PCT vs AIT porphyria

A

AIT- neuro
PCT- skin lesions

91
Q

3 major catecholamines

A

dopamine, norepinephrine & epinephrine

92
Q

T or F: epinephrine is a hormone & dopamine & norepinephrine are neurotransmitters

A

T

93
Q

what are dopamine, norepinephrine & epinephrine synthesized from?

A

tyrosine

94
Q

histamine- how formed & what it does

A

decarboxylation reaction, vasodilator, allergies, inflammation & regulates gastric acid secretion

95
Q

serotonin synthesis

A

from tryptophan via decarboxylation

96
Q

creatine synthesis

A

glycine, arginine & methionine

97
Q

what occurs with MSG

A

excess glutamate goes to the brain

98
Q

our bodies naturally contain ( ) g of free glutamate

A

10

99
Q

how much free glutamate in brain vs muscle

A

brain- 2.3g
muscle-6g

100
Q

what 2 molecules transport nitrogen from muscle to liver

A

alanine & glutamine

101
Q

2 alanine precursors

A

glutamate & pyruvate

102
Q

2 aspartate precursors

A

glutamate & oxalocacetate

103
Q

2 glutamate precursors

A

alanine & a-ketoglutarate

BMSC 230 #2 (15 decks)

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