Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

BMSC 230 > Chapter 30 - AA Degradation and the Urea Cycle > Flashcards

Chapter 30 - AA Degradation and the Urea Cycle Flashcards

1
Q

T/F: There is no protein whose sole job is to act as a storage depot for amino acids

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

amino acid input in animals

A
  • protein turnover
  • dietary proteins
  • amino acid biosynthesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

amino acid utilization in animals

A
  • synthesis of proteins
  • synthesis of nitrogenous molecules
  • degradation of amino acids carbon skeleton (acetyl coA)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

half-life of regulatory proteins

A

minutes to hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

half-life of collagen

A

weeks/months/years

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

2 major protein degradation pathways

A
  • ubiquitin-proteasome pathway

- chemical signals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

average dietary intake of protein

A

70-100g/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Generally, proteins are too large to be absorbed intact so….

A

they are digested into amino acids and di- and tri- peptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

proteolysis

A

the hydrolytic cleavage of proteins by proteases; occurs in stomach and small intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

endopeptidases

A
  • trypsin
  • chemotrypsin
  • elastase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

exopeptidases

A
  • carboxypeptidases A + B

- amino peptidases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

acidic environments…

A

denature proteins and enhance proteolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

gastroesophageal reflux disease (GERD)

A

a condition where the stomach acid leaks back to the esophagus
-The K+/H+ pump in the
membrane of specialized stomach cells pumps protons into the stomach in exchange for K+ at the expense of ATP hydrolysis
-generates acidic environment and releases heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

medications for GERD

A
  • antacids
  • histamine H2 receptor clockers
  • proton pump inhibitors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

zymogens

A

inactive proteolytic enzymes so that they don’t breakdown proteins in the cells where they are made and stored

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how are zymogens activated?

A

by proteolysis, which allows for proper folding of the enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

pepsin

A

preferentially cleaves pepDde bonds between hydrophobic amino acids and aromaDc amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

trypsin

A

cleaves peptide bonds following Arg or Lys residues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

chymotrypsin

A

preferentially cleaves peptide bonds after an aromatic amino acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

elastase

A

cuts after amino acids with smaller, hydrophobic side chains such as Glycogen, Ala

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

T/F: proteases self-inactivate

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Excess amino acids are not secreted or stored, so have to be……

A

metabolized to other molecules that can be excreted or used for other purposes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

transamination reaction

A

reversible reaction that transfers amino group to a-KG

-catalyzed by aminotransferase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

obligatory step of transamination

A

degradation of amino acids (except Lys and Thr and Pro)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
aminotransferases/transaminases required the coenzyme _________________.
pyridoxal phosphate; derived from pyridoxine (vit B6)
26
glutamate + pyruvate -->>
alanine + a-KG | -catalyzed by alanine transaminase
27
glutamate + oxaloacetate -->>
aspartate + a-KG | -catalyzed by AST
28
fate of glutamate in liver
transported to mitochondria and undergoes oxidative deamination to release ammonia
29
ratio of ammonia vs ammonium depends on?
pH | -pH 7.4 = 98.3% NH4+ (ammonium)
30
oxidative deamination of glutamate
- reversible rxn that removes amino group from Glu as NH4+ - catalyzed by glutamate dehydrogenase - in mitochondrial matrix
31
coenzymes of glutamate dehydrogenase
NAD+ and NADP+
32
positive allosteric modulator of glutamate dehydrogenase
ADP
33
negative allosteric modulator of glutamate dehydrogenase
GTP
34
high concentration of ______ is toxic
NH4+
35
NH4+ is converted to what in the liver?
urea
36
How does Ammonia that is Produced in Non-Liver Tissues get to the Liver so it can be Converted to Urea? (in most tissues)
- NH4+ reacts w/ glutamate to form glutamine (catalyzed by glutamine synthetase) - glutamine is a nontoxic storage and transport for of NH4+ - it is transported via blood to liver - NH4+ released from Gln by cleavage by glutaminase
37
How does Ammonia that is Produced in Non-Liver Tissues get to the Liver so it can be Converted to Urea? (in muscle)
- glutamate transfers amino group to pyruvate to form alanine - alanine leaves muscle into blood to liver - undergoes transamination to release amino group as ammonium - ALSO, glutamine can be formed from glutamate and released from muscle to liver
38
the urea cycle
cyclical pathways whereby excess NH4+ is converted to urea | -occurs in liver
39
precursors of urea
NH4+, CO2, and aspartate
40
where does the urea produced go?
it is secreted into the blood, filtered by kidney, then excreted in urine.
41
carbamoyl phosphate synthesis
- rate limiting step, regulated - requires 2 ATP - catalyzed by carmaboyl phosphate synthetase I (CPSI) (requires N-acetylglutamate as allosteric activator)
42
how is N-acetylglutamate formed?
from acetylCoA and Glu by N-acetylGlu synthase (stimulated by arginine)
43
some of the glutamate is used to form _____ which provides the second ammonium group
aspartate
44
advantages of clustering
- rapid rxn rates - intermediates remain in complex - conc of intermediates is high - intermediates do not undergo side rxns
45
___ and ______ link the urea cycle and the citric acid cycle
Asp. and fumarate
46
urea cycle overall rxn
Asp + NH4+ + HCO3-, + 3ATP --> urea, fumarate, 2ADP + AMP + 2Pi + PPi
47
ammoniotelic organisms
release ammonia directly (usually aquatic organisms)
48
uricotelic organisms
secrete nitrogen as the purine uric acid, require little water -generally used by organisms that can't afford to lose water: reptiles, birds
49
sources of free NH4+
- dietary and body protein - kidneys - amines (norepinephrine) - purine and pyrimidine catabolism
50
major source of ammonia
amino acids from diet or protein turnover via transdeamination in liver
51
While ammonia is constantly being produced, its level in the blood are kept low by what mechanisms?
- formation of urea - formation of glutamate in muscle by glutamate dehydrogenase - formation of glutamine in most tissues by glutamine synthetase
52
hyperammonemia
- ammonia is particularly toxic to CNS | - brain tries to reduce levels by synthesizing glutamine from glutamate
53
increased levels of glutamine
Glutamine is an osmolyte in astrocytes, which causes an uptake of water and thus brain swelling
54
decreased levels of glutamate
Glutamate is itself a neurotransmitter, but also a substrate for the synthesis of a second neurotransmitter, GABA (gamma aminobutyrate); so neurotransmitter function is affected
55
symptoms of hyperammonemia
tremors, slurring of speech, blurred vision, cerebral edema, coma
56
Causes of hyperammonemia?
- acquired: liver damage | - congenital: genetic
57
acquired hyperammonemia
- liver damage from viral hepatitis, hepatotoxins | - when liver becomes cirrhotic
58
congenital hyperammonemia
-defects in genes coding for all 5 urea cycle enzymes
59
treatments for hyperammonemia
- early treatment regimen was to inhibit protein intake and increase caloric intake to reduce amino acid catabolism - more recent, compounds administered that bind amino acids, forming compounds excreted in urine
60
compounds that are administered to bind to amino acid to treat hyperammonemia target glutamine. why?
- not an essential AA - main carrier of ammonium from peripheral tissues - contain 2 amino groups
61
glucogenic
amino acids that are catabolized to pyruvate or an intermediate of the TCA cycle, since they can be used for glucose synthesis via gluconeogenesis
62
ketogenic
amino acids that are catabolized to acetyl CoA or acetoacetate; can lead to formation of FA, ketone bodies, or their precursors
63
Most ketogenic amino acids are also glycogenic except for...
lysine and leucine
64
T/F: gluconeogenesis is a simple reversal of glucose synthesis
FALSE
65
catabolic pathways for Top, Ala, Sec, and Cys
can all be converted to pyruvate
66
catabolic pathway for Asparagine in mitochondria
converted to oxaloacetate
67
catabolic pathway for phenylalanine
converted to tyrosin (catalyzed by Phe hydroxylase) --> fumarate or acetylCoA
68
phenylketonuria
- best known of the diseases of amino acid metabolism - caused by absence or deficiency of Phe hydroxylase - phenylalanine accumulates and cannot be converted to tyrosine for complete degradation
69
catabolism of branched-chain amino acids (Leucine, Isoleucine, and valine)
yield acetyl CoA, acetoacetate, or succinyl CoA
70
Specialized products that are derived from amino acids
nitrogen-containing molecules such as porphyrins, some hormones, neurotransmitters, purines/pyrimidines
71
poryphyrins
-cyclic compounds that bind primarily Fe2+ or Fe3+ (heme)
72
Carbon and nitrogen atoms in porphyrins are derived from..
glycine and succinyl CoA
73
porphyrias
rare genetic disease which lead to defects in biosynthesis of porphyrins and accumulation of intermediates
74
Conversion of amino acids to catecholamines
synthesized from tyrosine | -dopamine, norepinephrine, epinephrine
75
Conversion of amino acids to histamine
- mediates many responses (allergic and inflammatory responses, gastric acid secretions) - stronf vasodilator - formed from decarboxylation of histidine
76
Conversion of amino acids to serotonin (5-hydroxytryptamine)
- synthesized from tryptophan | - pain, sleep, temp, blood pressure, appetite, well-being
77
Conversion of amino acids to creatine
- synthesized from glycine, guanidine group of arginine and Mat - small pool of energy source in phosphorylated form

BMSC 230 (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions