amino acid metabolism Flashcards
1
Q
what protein stores amino acids?
A
there is none
2
Q
protein turnover is about ___g / day
A
300-400
3
Q
what are the 2 major protein degradation paths?
A
1) ubiquitin-proteasome path
2) chem signals
4
Q
the hydrolytic cleavage of proteins by proteases
A
proteolysis
5
Q
proteolysis occurs in ___ and ___
A
stomach; small intestine
6
Q
purpose of chewing?
A
liquification, neural effects (histamine), surface area
7
Q
gastric juice contains:
A
HCl (100mmol/L), pepsin, gastrin
8
Q
pH alters ___ and ___ bonds
A
disulfide; hydrogen
9
Q
pathway of protein digestion?
A
mouth–>stomach–>small intestine–>endothelial cells–>portal vein–>liver/peripheral tissues
10
Q
inactive form of proteases are called:
A
zymogens
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
12
Q
wat does GERD stand for?
A
gastroesophageal reflux disease
13
Q
example of proton pump inhibitor med?
A
prevacid
14
Q
example of histamine H2 receptor blocker?
A
zantac
15
Q
zymogens are activated by ___
A
proteolysis
16
Q
why are proteolytic enzymes stored as zymogens?
A
so don’t break down proteins in cells where they are made/stored
17
Q
2 steps of zymogen activation?
A
1) autocleavage
2) autocleaved activated enzymes activate the other zymogens
18
Q
preferentially cleaves peptide bonds between hydrophobic and aromatic a.a.
A
pepsin
19
Q
less specific proteolytic enzymes that cleave at ends of proteins are called:
A
exopeptidases (carboxy, amino)
20
Q
preferentially cleaves peptide bonds after aromatic a.a.
A
chymotrypsin
21
Q
cleaves peptide bonds following Arg or Lys
A
trypsin
22
Q
cuts after a.a. w/ smaller hydrophobic side chains
A
elastase
23
Q
why are there so many diff proteolytic enzymes?
A
enable diff substrate specificities to allow proteins cut into small bits rapidly
24
Q
in transamination, amino acids are all funneled into ____
A
L-glutamate
25
glutamate-->alpha ketoglutarate called?
oxidative deamination (remove NH4)
26
urea only produced in ___
liver
27
transamination requires vit. ____
B6
28
transamination reaction doesn't happen for _____
Lysine and Threonine
29
transamination has a Keq that is approximately ___
1 (reversible rxn)
30
__ of aminotransferases are used as a diagnostic tool
isozymes
31
3 pairings we need to know?
alpha ketoglutarate/glutamate; pyruvate/alanine; aspartate/oxaloacetate
32
what is the fate of glutamate in liver?
transport to mito and undergo oxidative deamination to release ammonia
33
oxidative deamination of glutamate by ____
glutamate dehydrogenase (remove amino group from Glu)
34
NH3 is ___, NH4 is ___
ammonia; ammonium (odourless, more common in body)
35
glutamate dehydrogenase is activated by ___, inhibited by ___
ADP, GTP
36
coenzymes of glutamate dehydrogenase?
NAD or NADP
37
NH4 reacts with glutamate to form ___, by enzyme called ____; this happens in tissue other than _____
glutamine; glutamine synthetase; muscle/liver
38
glutaminase is found in ___ to release free ammonia to convert to urea
mitochondria
39
glutamate forms ____ in muscle by transferring amino group to ___
alanine; pyruvate (gluconeogenesis to form gluc)
40
urea produced is __ into blood, ___ by kidney, ___ in urine
secreted; filtered; excreted
41
urea cycle occurs in ___ thru series of rxns in __ and __ of cell
liver; cytosol; mito
42
precursors of urea
NH4, CO2, aspartate
43
very good disinfectant/cleaner, found in old pee
ammonia
44
uncatalyzed elimination of urea is ____, urease catalyzed hydrolysis is ____
slow; fast
45
rate limiting step with this enzyme in urea synthesis
carbamoyl phosphate synthetase 1
46
CPS1 needs ___ as allosteric activator and obligatory (ne___ ATP
N-acetylglutamate ; 2
47
N-acetylglutamate synth from _____ by synthase stimulated by ___
acetyl coA, glutamate; arginine
48
second ammonium group in urea cycle from ___
aspartate
49
carbamoyl phosphate and ____ results in citrulline
ornithine
50
why are cytosolic rxns in urea cycle clustered?
rapid rxns, intermediates remain in complex, [ ] intermediates high, no side rxns
51
enzyme that uses water to turn arginine to ornithine, and release urea
arginase
52
___ and ___ link urea cycle to TCA
Asp; fumarate
53
overall rxn of urea cycle?
Asp+NH3+HCO3+3ATP-->urea+fumarate+2ADP+AMP+2i+PPi
54
__ ATP equivalents needed form each urea cule
4
55
organisms that release ammonia directly are usually ___ and are referred to as ____
aquatic; ammoniotelic
56
organisms that release uric acid (slightly water soluble) because can't afford to lose water
reptiles, birds
57
reptiles and birds are examples of ____ organisms
uricotelic
58
major source of NH4?
dietary/body protein
59
in the liver, free ammonium produced from ________
serine, threonine, glutamine
60
in kidney, free ammonium gen by metabolism of glutamine by these enzymes:
glutaminase, glutamate dehydrogenase
61
ex. of monoamine that serve as hormone/neurotrans?
norepinephrine
62
how is blood ammonia left low?
formation of urea, form glutamate in muscle by glut dehydrogense, form glutamine in most tissues by glut synthetase
63
this condition shows how CNS particularly sensitive to ^ NH4
hyperammonemia
64
symptoms of hyperammonemia
tremors, slurring speech, blurred vision, cerebral edema, coma
65
glutamine is an ___ in astrocytes
osmolyte (brain swells)
66
glutamate is a substrate for synth of ____
GABA (gamma aminobutyrate)
67
2 causes of hyperammonemia?
liver damage (acquired), genetic (congenital)
68
liver damage can result from ____
viral hepatitis, hepatotoxins (alcohol)
69
compound administered that treats congenital hyperammonemia
phenylbutyrate (bind Glutamine)
70
in congenital hyperammonemia, why are defects in arginase less severe?
arginine contains 3 amino groups and can be excreted in urine
71
old treatment for congenital hyperammonemia?
inhibit protein intake, increase caloric intake in other things
72
a.a. catabolized to pyruvate or intermediate of TCA cycle are called?
glucogenic
73
a.a. catabolized to acetyl coA or acetoacetate are called?
ketogenic
74
the two exclusively ketogenic a.a.?
lysine, leucine
75
4 a.a. that channel to make pyruvate
Trp, Ala, Ser, Cys
76
path of Asn in mito?
Asn-->aspartate-->oxaloacetate
77
normal path of Phe?
Phe-->tyrosine-->acetyl coA/fumarate
78
PKU path of Phe?
Phe-->phenylpyruvate-->phenylacetate/phenyllactate
79
what is PKU?
phenylketonuria
80
symptoms of PKU?
mental retardation, fail to walk/talk, seizure, tremor, fail to grow, light skin/hair
81
how to treat PKU?
diet restrict Phe, no aspartame
82
tyrosine is precursor for ___
melanin
83
path of valine, isoleucine, leucine?
-->branched chain aminotransferase-->alpha keto acids-->branched chain alpha keto acid dehydrogenase complex-->acyl CoA derivatives
84
interference with dehydrogenase complex cause ____ disease
maple syrup urine
85
medical condition involving defect in tyrosine-->melanin enzyme
albinism
86
Four pyrrole rings linked together, with varying sidechains
porphyrin
87
porphyrins derive C and N from _____
glycine and succinyl CoA
88
porphyrin mainly binds :
Fe 2/3+
89
most common porphyria that is autosomal dominant, triggered by fasting/insufficient carbs (on IV)-->symptoms include abdominal pain, motor weakness, neuropsych prob
acute intermittent porphyria
90
porphyria that is characterized by red urine, teeth fluoresce red in UV, skin sensitive to light, anemic; associated with vampire myth
porphyria cutanea tarda
91
catecholamines are synthesized from ____
tyrosine
92
examples of catecholamines?
dopamine, norepinephrine, epinephrine
93
molecule that mediates many allergic/inflammatory responses, is a strong vasodilator, and is formed from decarboxylated histidine
histamine
94
found in intestinal mucosa and in CNS, mediates a sense of well-being, converted to melatonin, synthesized from tryptophan
serotonin
95
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
creatine
96
On average, we eat ___g of glutamate from protein sources and ___g from MSG
13; 0.6
97
overall reaction of nitrogen cycle?
N2+10H+16ATP+8e-->2NH4+H2+16ADP+16Pi
98
forms of nitrogen available to plants:
ammonium, nitrates
99
______ provide entry points for assimilation of ammonium into biomolecules
glutamate and glutamine
100
inhibitors of glutamine synthetase:
glycine, alanine, CTP, histidine, glucosamine 6-P, AMP, Tryptophan, carbamoyl P
101
glutamine synthetase is regulated by _____
allosteric effectors (8 of them) covalent mods
102
all inhibitors of glutamine synthetase contain ____
Nitrogen
103
adenylylation occurs on ___ residue
tyrosine
104
What is SAM and what does it do?
S-Adenosylmethionine; for 1-C transfers to N and O atoms (eg. norepinephrine --> epinephrine)
105
Diet folate-->DHF-->THF need ____ to catalyze and ____ as reducing agent
DHFR; NADPH
106
1C transfers using THF
methionine synth, serine synth
107
all aa synth from intermediates of _______ pathways
TCA, PPP, glycolytic
108
nonessential amino acids:
alanine, asparagine, aspartate, glutamate, serine
109
why are some a.a. conditionally essential?
during illness (nutritional insult), in young developing animals (high requirement)
110
4 types of feedback inhibition
product inhibition, sequential, concerted, enzyme multiplicity
