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

module 11- amino acid degradation & urea cycle Flashcards

(103 cards)

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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
excess amino groups are secreted in the form of ( ), while carbon skeletons are converted to ( )
urea, a-keto acids
26
what are a-keto acids used for
energy production or gluconeogenesis
27
transamination
amino groups form 1 amino acid
28
oxidative deamination
amino group from glutamate is released as NH4
29
transdeaminination
transamination & deamination combined
30
where does urea production occur
liver
31
what is the 1st step in amino acid degradation
transamination
32
what do aminotransferases do?
transfer amino group from a-ketoglutarate to glutamate
33
what do aminotransferases require as a coenzyme?
pyridoxal phosphate- derived from vitamin B6
34
the nomenclature for aminotransferases are based on?
amino acid donor
35
alaine aminotransferase
transfers amino group from alanine to a-ketoglutarate to produce glutamate & pyruvate
36
aspartate aminotransferase
transfers amino group from aspartate to a-ketoglutarate to produce glutamate & oxaloacetate
37
T or F: elevated aminotransferases levels can be used to diagnose medical conditions
T
38
at pH of 7.4, most is in ( ) form
NH4 form
39
T or F: ammonium is odorless
T
40
glutamate undergoes oxidative deamination which releases ( ) + ( )
NH4 + a-ketoglutarate
41
T or F: we have very little free ammonia in our bodies
T
42
where is free ammonium produced? why?
mitochondria, can be used to form urea which prevents accumulation
43
glutamate dehydrogenase
removes amino group & oxidation of glutamate
44
electrons removed from glutamate by glutamate dehydrogenase are captured as?
NADH or NADPH
45
in most tissues, free ammonium is incorporated into ( ) by ( )
glutamine, glutamine synthetase
46
T or F: most amino acids cannot get out of cells
T
47
what amino acid can leave cells
glutamine
48
glutaminase- location & what does it do
liver, uses water to cleave ammonium off of glutamine
49
most ammonim gets transported out of the muscle in the form of?
alanine
50
glucose-alanine cycle
alanine-> glutamate -> pyruvate -> glucose -> pyruvate
51
contributions to the glutamate pool come from
alanine from muscle & glutamine from tissues
52
glutamate is acted on by glutamate dehydrogenase to?
releases ammonium
53
urea is ( ) soluble in water
highly
54
precursors for urea are?
NH4, CO2 & aspartate
55
urea cycle
reactions that occur in the mitochondira & the cytosol
56
where does the urea cycle start? why?
mitochondria, bc ammonia is released here
57
what is the rate limiting enzyme for urea cycle
carbamoyl phosphate synthetase
58
carbamoyl phosphate synthetase I- location
mitochondrial matrix
59
obligate allosteric activator of carbomoyl phosphate synthetase I
N-acetylglutamate
60
obligate activator
required for its target enzyme to have activity
61
how is N-acetylglutamate stimulated
presence of arginine
62
where do the 2 amino groups on urea come from?
free ammonium & aspartate
63
urea cycle part 2
urea is produced & ornithine is replenished
64
citrulline is acted upon by ?
argininosuccinate synthetase
65
when argnine is acted upon by the hydrolase arginase, what 2 things are produced?
urea & ornithine
66
what 3 enzymes are clustered together in a complex
argininosuccinate synthetase, argininosuccinase & arginase
67
what 2 molecules link the urea cycle & the citric acid cycle
fumarate & aspartate
68
how is the urea cycle regulated?
by N-acetylglutamate & arginine
69
how many ATP are needed per urea molecule formed
3
70
ammoniotelic
secrete nitrogen as ammonium
71
ureotelic
secrete urea
72
how do birds/reptiles ecrete excess nitrogen
uric acid
73
hyperammonemia
too much ammonium
74
what 2 amino acids can form ammonium
serine & theronine
75
acquired vs congential hyperammonemia
acquired- liver damage - hepatitis or alcohol congential- mutation defects
76
glucogenic amino acid & example
catabolized to pyruvate or intermediate of CAC alanine
77
ketogenic amino acid & example
catabolized to acetyl CA or acetoacetate
78
what 5 amino acids are ketogenic & glucogenic
tryptophan, tyrosine, threonine, phenylalanine, and isoleucine
79
phenylketonuria- what is it, symptoms
deficiency in phenylalanine hydroxylase, CNS symptoms
80
maple syrup urine disease- what is it & symptoms
deficiency in dehydrogenase complex, CNS symptoms
81
most genetic diseases affecting amino acid catabolism have ( ) effects
CNS
82
T or F: genetic diseases affecting amino acid catabolism are very rare
T
83
porphyrins
cyclic compounds that bind Fe 2+ or Fe 3+
84
all carbon & nitrogen atoms in porphyrins are contributed by ( ) & ( )
glycine & succinyl CoA
85
1st step in porphyrins pathway
fusion of succinyl CoA & glycine to form ALA
86
porphyrias
rare genetic diseases due to defects in porphyrin synthesis & accumulation of intermediates
87
acute intermittent porphyria
defect in PBP deaminase
88
how do porphyrin diseases different?
accumulation of different intermediates
89
what is most common porphyria?
acute
90
PCT vs AIT porphyria
AIT- neuro PCT- skin lesions
91
3 major catecholamines
dopamine, norepinephrine & epinephrine
92
T or F: epinephrine is a hormone & dopamine & norepinephrine are neurotransmitters
T
93
what are dopamine, norepinephrine & epinephrine synthesized from?
tyrosine
94
histamine- how formed & what it does
decarboxylation reaction, vasodilator, allergies, inflammation & regulates gastric acid secretion
95
serotonin synthesis
from tryptophan via decarboxylation
96
creatine synthesis
glycine, arginine & methionine
97
what occurs with MSG
excess glutamate goes to the brain
98
our bodies naturally contain ( ) g of free glutamate
10
99
how much free glutamate in brain vs muscle
brain- 2.3g muscle-6g
100
what 2 molecules transport nitrogen from muscle to liver
alanine & glutamine
101
2 alanine precursors
glutamate & pyruvate
102
2 aspartate precursors
glutamate & oxalocacetate
103
2 glutamate precursors
alanine & a-ketoglutarate

BMSC 230 #2 (15 decks)

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