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Bmsc230 > amino acid metabolism > Flashcards

amino acid metabolism Flashcards

1
Q

what protein stores amino acids?

A

there is none

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2
Q

protein turnover is about ___g / day

A

300-400

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3
Q

what are the 2 major protein degradation paths?

A

1) ubiquitin-proteasome path

2) chem signals

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4
Q

the hydrolytic cleavage of proteins by proteases

A

proteolysis

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5
Q

proteolysis occurs in ___ and ___

A

stomach; small intestine

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6
Q

purpose of chewing?

A

liquification, neural effects (histamine), surface area

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7
Q

gastric juice contains:

A

HCl (100mmol/L), pepsin, gastrin

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8
Q

pH alters ___ and ___ bonds

A

disulfide; hydrogen

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9
Q

pathway of protein digestion?

A

mouth–>stomach–>small intestine–>endothelial cells–>portal vein–>liver/peripheral tissues

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10
Q

inactive form of proteases are called:

A

zymogens

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11
Q

purpose of K/H pump in membrane of specialized stomach cells?

A

H+ go into stomach, K+ go out to gen. acidic enviro and release heat

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12
Q

wat does GERD stand for?

A

gastroesophageal reflux disease

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13
Q

example of proton pump inhibitor med?

A

prevacid

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14
Q

example of histamine H2 receptor blocker?

A

zantac

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15
Q

zymogens are activated by ___

A

proteolysis

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16
Q

why are proteolytic enzymes stored as zymogens?

A

so don’t break down proteins in cells where they are made/stored

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17
Q

2 steps of zymogen activation?

A

1) autocleavage

2) autocleaved activated enzymes activate the other zymogens

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18
Q

preferentially cleaves peptide bonds between hydrophobic and aromatic a.a.

A

pepsin

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19
Q

less specific proteolytic enzymes that cleave at ends of proteins are called:

A

exopeptidases (carboxy, amino)

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20
Q

preferentially cleaves peptide bonds after aromatic a.a.

A

chymotrypsin

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21
Q

cleaves peptide bonds following Arg or Lys

A

trypsin

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22
Q

cuts after a.a. w/ smaller hydrophobic side chains

A

elastase

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23
Q

why are there so many diff proteolytic enzymes?

A

enable diff substrate specificities to allow proteins cut into small bits rapidly

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24
Q

in transamination, amino acids are all funneled into ____

A

L-glutamate

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25
Q

glutamate–>alpha ketoglutarate called?

A

oxidative deamination (remove NH4)

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26
Q

urea only produced in ___

A

liver

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27
Q

transamination requires vit. ____

A

B6

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28
Q

transamination reaction doesn’t happen for _____

A

Lysine and Threonine

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29
Q

transamination has a Keq that is approximately ___

A

1 (reversible rxn)

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30
Q

__ of aminotransferases are used as a diagnostic tool

A

isozymes

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31
Q

3 pairings we need to know?

A

alpha ketoglutarate/glutamate; pyruvate/alanine; aspartate/oxaloacetate

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32
Q

what is the fate of glutamate in liver?

A

transport to mito and undergo oxidative deamination to release ammonia

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33
Q

oxidative deamination of glutamate by ____

A

glutamate dehydrogenase (remove amino group from Glu)

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34
Q

NH3 is ___, NH4 is ___

A

ammonia; ammonium (odourless, more common in body)

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35
Q

glutamate dehydrogenase is activated by ___, inhibited by ___

A

ADP, GTP

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36
Q

coenzymes of glutamate dehydrogenase?

A

NAD or NADP

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37
Q

NH4 reacts with glutamate to form ___, by enzyme called ____; this happens in tissue other than _____

A

glutamine; glutamine synthetase; muscle/liver

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38
Q

glutaminase is found in ___ to release free ammonia to convert to urea

A

mitochondria

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39
Q

glutamate forms ____ in muscle by transferring amino group to ___

A

alanine; pyruvate (gluconeogenesis to form gluc)

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40
Q

urea produced is __ into blood, ___ by kidney, ___ in urine

A

secreted; filtered; excreted

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41
Q

urea cycle occurs in ___ thru series of rxns in __ and __ of cell

A

liver; cytosol; mito

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42
Q

precursors of urea

A

NH4, CO2, aspartate

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43
Q

very good disinfectant/cleaner, found in old pee

A

ammonia

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44
Q

uncatalyzed elimination of urea is ____, urease catalyzed hydrolysis is ____

A

slow; fast

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45
Q

rate limiting step with this enzyme in urea synthesis

A

carbamoyl phosphate synthetase 1

46
Q

CPS1 needs ___ as allosteric activator and obligatory (ne___ ATP

A

N-acetylglutamate ; 2

47
Q

N-acetylglutamate synth from _____ by synthase stimulated by ___

A

acetyl coA, glutamate; arginine

48
Q

second ammonium group in urea cycle from ___

A

aspartate

49
Q

carbamoyl phosphate and ____ results in citrulline

A

ornithine

50
Q

why are cytosolic rxns in urea cycle clustered?

A

rapid rxns, intermediates remain in complex, [ ] intermediates high, no side rxns

51
Q

enzyme that uses water to turn arginine to ornithine, and release urea

A

arginase

52
Q

___ and ___ link urea cycle to TCA

A

Asp; fumarate

53
Q

overall rxn of urea cycle?

A

Asp+NH3+HCO3+3ATP–>urea+fumarate+2ADP+AMP+2i+PPi

54
Q

__ ATP equivalents needed form each urea cule

A

4

55
Q

organisms that release ammonia directly are usually ___ and are referred to as ____

A

aquatic; ammoniotelic

56
Q

organisms that release uric acid (slightly water soluble) because can’t afford to lose water

A

reptiles, birds

57
Q

reptiles and birds are examples of ____ organisms

A

uricotelic

58
Q

major source of NH4?

A

dietary/body protein

59
Q

in the liver, free ammonium produced from ________

A

serine, threonine, glutamine

60
Q

in kidney, free ammonium gen by metabolism of glutamine by these enzymes:

A

glutaminase, glutamate dehydrogenase

61
Q

ex. of monoamine that serve as hormone/neurotrans?

A

norepinephrine

62
Q

how is blood ammonia left low?

A

formation of urea, form glutamate in muscle by glut dehydrogense, form glutamine in most tissues by glut synthetase

63
Q

this condition shows how CNS particularly sensitive to ^ NH4

A

hyperammonemia

64
Q

symptoms of hyperammonemia

A

tremors, slurring speech, blurred vision, cerebral edema, coma

65
Q

glutamine is an ___ in astrocytes

A

osmolyte (brain swells)

66
Q

glutamate is a substrate for synth of ____

A

GABA (gamma aminobutyrate)

67
Q

2 causes of hyperammonemia?

A

liver damage (acquired), genetic (congenital)

68
Q

liver damage can result from ____

A

viral hepatitis, hepatotoxins (alcohol)

69
Q

compound administered that treats congenital hyperammonemia

A

phenylbutyrate (bind Glutamine)

70
Q

in congenital hyperammonemia, why are defects in arginase less severe?

A

arginine contains 3 amino groups and can be excreted in urine

71
Q

old treatment for congenital hyperammonemia?

A

inhibit protein intake, increase caloric intake in other things

72
Q

a.a. catabolized to pyruvate or intermediate of TCA cycle are called?

A

glucogenic

73
Q

a.a. catabolized to acetyl coA or acetoacetate are called?

A

ketogenic

74
Q

the two exclusively ketogenic a.a.?

A

lysine, leucine

75
Q

4 a.a. that channel to make pyruvate

A

Trp, Ala, Ser, Cys

76
Q

path of Asn in mito?

A

Asn–>aspartate–>oxaloacetate

77
Q

normal path of Phe?

A

Phe–>tyrosine–>acetyl coA/fumarate

78
Q

PKU path of Phe?

A

Phe–>phenylpyruvate–>phenylacetate/phenyllactate

79
Q

what is PKU?

A

phenylketonuria

80
Q

symptoms of PKU?

A

mental retardation, fail to walk/talk, seizure, tremor, fail to grow, light skin/hair

81
Q

how to treat PKU?

A

diet restrict Phe, no aspartame

82
Q

tyrosine is precursor for ___

A

melanin

83
Q

path of valine, isoleucine, leucine?

A

–>branched chain aminotransferase–>alpha keto acids–>branched chain alpha keto acid dehydrogenase complex–>acyl CoA derivatives

84
Q

interference with dehydrogenase complex cause ____ disease

A

maple syrup urine

85
Q

medical condition involving defect in tyrosine–>melanin enzyme

A

albinism

86
Q

Four pyrrole rings linked together, with varying sidechains

A

porphyrin

87
Q

porphyrins derive C and N from _____

A

glycine and succinyl CoA

88
Q

porphyrin mainly binds :

A

Fe 2/3+

89
Q

most common porphyria that is autosomal dominant, triggered by fasting/insufficient carbs (on IV)–>symptoms include abdominal pain, motor weakness, neuropsych prob

A

acute intermittent porphyria

90
Q

porphyria that is characterized by red urine, teeth fluoresce red in UV, skin sensitive to light, anemic; associated with vampire myth

A

porphyria cutanea tarda

91
Q

catecholamines are synthesized from ____

A

tyrosine

92
Q

examples of catecholamines?

A

dopamine, norepinephrine, epinephrine

93
Q

molecule that mediates many allergic/inflammatory responses, is a strong vasodilator, and is formed from decarboxylated histidine

A

histamine

94
Q

found in intestinal mucosa and in CNS, mediates a sense of well-being, converted to melatonin, synthesized from tryptophan

A

serotonin

95
Q

synthesized from glycine, guanidino group of arginine and methionine; when phosphorylated it is a high energy compound found in muscle and serves as short term energy source

A

creatine

96
Q

On average, we eat ___g of glutamate from protein sources and ___g from MSG

A

13; 0.6

97
Q

overall reaction of nitrogen cycle?

A

N2+10H+16ATP+8e–>2NH4+H2+16ADP+16Pi

98
Q

forms of nitrogen available to plants:

A

ammonium, nitrates

99
Q

______ provide entry points for assimilation of ammonium into biomolecules

A

glutamate and glutamine

100
Q

inhibitors of glutamine synthetase:

A

glycine, alanine, CTP, histidine, glucosamine 6-P, AMP, Tryptophan, carbamoyl P

101
Q

glutamine synthetase is regulated by _____

A

allosteric effectors (8 of them) covalent mods

102
Q

all inhibitors of glutamine synthetase contain ____

A

Nitrogen

103
Q

adenylylation occurs on ___ residue

A

tyrosine

104
Q

What is SAM and what does it do?

A

S-Adenosylmethionine; for 1-C transfers to N and O atoms (eg. norepinephrine –> epinephrine)

105
Q

Diet folate–>DHF–>THF need ____ to catalyze and ____ as reducing agent

A

DHFR; NADPH

106
Q

1C transfers using THF

A

methionine synth, serine synth

107
Q

all aa synth from intermediates of _______ pathways

A

TCA, PPP, glycolytic

108
Q

nonessential amino acids:

A

alanine, asparagine, aspartate, glutamate, serine

109
Q

why are some a.a. conditionally essential?

A

during illness (nutritional insult), in young developing animals (high requirement)

110
Q

4 types of feedback inhibition

A

product inhibition, sequential, concerted, enzyme multiplicity

Bmsc230 (13 decks)

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