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BIOCHEMISTRY S02 > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

(112 cards)

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1
Q

What are the essential amino acids?

A 
Phenylalanine
Valine
Threonine 
Tryptophan
Isoleucine
Methionine
Histidine
Arginine
Leucine
Lysine

PVT TIM HALL always ARGues, never Tyres [tires]

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2
Q

What amino acids are not necessary for protein synthesis but is formed during post-translational processing of COLLAGEN?

A

Hydroxyproline and Hydroxylysine

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3
Q

These are amino acids whose catabolism yields either acetoacetate or one of its precursors (acetyl CoA or acetoacetyl CoA)

A

Ketogenic amino acids: Leucine and Lysine

- can enter metabolic pathway of lipids

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4
Q

Which amino acids have Carbon skeletons that can enter both ketogenic and glucogenic pathways?

A

Tryptophan, Isoleucine, Phenylalanine, Tyrosine

WIFY has it all

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5
Q

What alpha-ketoacid is used for the transamination to Alanine and how many carbons does it have?

A

Pyruvate;

3 carbons like alanine

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6
Q

What enzyme and coenzymes are needed for transamination of Pyruvate to Alanine?

A

Aminotransferase and Pyridoxal phosphate

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7
Q

What is the enzyme or serum marker for the transamination of oxaloacetate to aspartate?

A

Aspartate aminotransferase (aminotransaminase) / Serum Glutamic Oxaloacetic Transaminase

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8
Q

What is the only amino acid that undergoes reversal of oxidative deamination?

A

Glutamate

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9
Q

Glutamate is formed by which type of reaction with the citric acid cycle α-ketoglutarate?

A

reductive amination

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10
Q

What catalyzes the formation of glutamate from alpha-ketoglutarate?

A

Glutamate dehydrogenase (for reductive amination)

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11
Q 
The pathway of biosynthesis of glutamate will be important for the catabolism of which organic molecule?
A. O2
B. C
C. N
D. H+
A

C. Nitrogen

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12
Q

What are the coenzymes of Glutamate dehydrogenase?

A

NAD+ or NADP+

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13
Q

What are the Amino acids that form α-ketoglutarate via glutamate?

A

Glutamine
Arginine
Proline
Histidine

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14
Q

What is the intermediate in the amination of glutamate to glutamine?

A

γ-glutamylphosphate

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15
Q

What is the enzyme and coenzyme for the amination of glutamate to glutamine?

A

Glutamine synthase (ATP)

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16
Q

Circulating glutamine is removed by the liver and the kidneys and deaminated by ________ to produce glutamate and ammonia (NH3)

A

Glutaminase

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17
Q

What is the amide donor in asparagine synthesis?

A

Glutamine

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18
Q

What is the coenzyme and cofactor of Asparagine synthetase?

A

ATP and Mg2+

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19
Q

What is the intermediate formed in step 3 of proline synthesis?

A

Δ1-pyrrole-5-caryboxylic acid (carboxylate)

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20
Q

What are the reactions in proline synthesis?

A

reductive reactions and cyclization

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21
Q

What are the enzymes per step in proline synthesis in sequence?

A

Glutamate kinase (ATP) >
Glutamate semialdehyde dehydrogenase (NADPH) >
None but Spontaneous cyclization >
Pyrroline carboxylase reductase (NADPH)

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22
Q

Which intermediate of glycolysis is used in the synthesis of serine?

A

3-phosphoglycerate (the product of step 7)

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23
Q

What are the reactions and respective enzymes involved in the synthesis of serine?

A

1 - Oxidation via Phosphoglycerate dehydrogenase (NAD+)
2 - Transamination via Phosphoserine aminotransferase (PSAT1)
3 - Hydrolytic dephosphorylation via Phosphoserine phosphorylase (need water)

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24
Q

What amino acid can also be used for serine synthesis?

A

Glycine

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25
What is the enzyme and coenzymes needed for the formation of serine from Glycine?
Serine hydroxymethyl transferase with PLP and MTHF
26
What is the reaction, enzyme and coenzyme for the conversion of serine to pyruvate?
dehydration via serine dehydratase with PLP
27
What are the amino acid substrates for cysteine synthesis?
Methionine and Serine
28
What is the enzyme needed to form Cystathionine from Homocysteine?
Cystathionine-beta-synthase
29
What is the enzyme and coenzyme needed to remethylate Homocysteine to Methionine?
Methionine Synthase
30
What are the coenzymes needed to remethylate homocysteine back to methionine?
MTHF (B9) to give methyl group to cobalamin (B12) forming methyl cobalamin which will then give methyl to homocysteine
31
What is the coenzyme needed to form cystathionine from homocysteine?
Vitamin B6 or PLP
32
What is the enzyme that converts cystathionine to cysteine and homoserine?
Cystathionine lyase
33
Why can't dietary Tyr replace Phe?
Because Tyr synthesis from Phe is irreversible
34
What is the enzyme and coenzyme required for the formation of Tyr from Phe?
Phenylalanine hydroxylase and Tetrahydrobiopterin (BH4)
35
What odor is manifested by PKU patients?
Mousy odor
36
Why does PKU result to hypopigmentation?
Due to decreased melanin from decreased tyrosine
37
__________ is important in stabilizing the triple-helical structure of collagen because it maximizes interchain hydrogen bond formation.
Hydroxyproline
38
What is the reaction and enzymes needed for the formation of collagen from proline and lysine residues
Hydroxylation via Prolyl or Lysyl hydroxylase
39
What are the respective alpha-ketoacids formed from the transamination of branched-chain amino acids and in which organ does this primarily takes place? What enzyme?
``` Valine = a-ketoisovalerate Isoleucine = a-ketomethylvalorate Leucine = a-ketoisocaproate ``` Skeletal muscles with Branched-Chain Aminotransferase (BCAT)
40
What enzyme converts the alpha-keto acids of branched-chain amino acids?
Branched-chain alpha-ketoacid Dehydrogenase (BCKAD)
41
What AA is the precursor of Selenocysteine?
Serine
42
What is the Selenium donor in the biosynthesis of Selenocysteine, and what coenzyme and anion is required for its formation?
Selenophosphate from ATP and Selenate (SeO4^2-)
43
In Sec Biosynthesis, what enzyme eliminates the phosphate from the phosphoserine on the tRNA then ligate onto the tRNA the selenium from the donor selenophosphate?
Selenocysteine synthase
44
_______ is an excess of ingested over excreted nitrogen that accompanies growth and pregnancy.
Positive nitrogen balance
45
______________ is where output exceeds intake, may follow surgery, advanced cancer, and the nutritional disorders kwashiorkor and marasmus.
Negative nitrogen balance
46
What are the coenzymes for Prolyl hydroxylase or Lysyl hydroxylase?
Ascorbic acid and Fe++
47
What is the cofactor deficient in Menkes syndrome affect which enzyme?
Copper = lysl oxidase
48
What enzyme functions in formation of covalent cross-links that strengthen collagen fibers
lysl oxidase
49
What are the enzymes involved in Ehlers-Danlos syndrome?
alpha- collagen-1, procollagen N-peptidase or lysyl hydroxylase
50
What are the 3 sources of amino acids?
▪ Degradation of endogenous (body) proteins → most are reutilized ▪ Exogenous (dietary) proteins ▪ Nonessential amino acids synthesized from simple intermediates of metabolism
51
What are the 3 routes for depleting/excreting AA?
▪ Synthesis of body protein ▪ Consumption of amino acids as precursors of essential nitrogen-containing small molecules ▪ Conversion of amino acids to glucose (gluconeogenesis), glycogen, fatty acids, and ketone bodies (ketogenesis), or oxidation to CO2 + H2O (not used in biosynthesis are used as fuel/energy)
52
_______ is the simultaneous synthesis and degradation of protein molecules
Protein turnover
53
``` Nitrogen leaves our body by formation of the following except: A. urea B. ammonia C. pyruvate D. acetyl-CoA E. glucose ```
E.
54
What is the half-life of regulatory proteins?
minutes to hours | Short-lived like misfolded proteins
55
What is the half-life of the majority of cells proteins?
Days to weeks | Long-lived protein
56
What is the half-life of collagen?
months to years | Structural protein = metabolically stable
57
The ubiquitin proteasome system happens in which part of the cell?
Cytosol | ATP-dependent
58
ATP-independent degradative enzyme system happens in which part of the cell?
lysosomes
59
What enzyme system is used to degrade plasma proteins?
ATP-independent degradative enzyme system in lysosomes
60
Endogenous proteins are degraded by which system?
ATP-dependent ubiquitin-proteasome system of the cytosol
61
What protease hydrolyzes peptide bonds and degrade them into amino acids
endopeptidase
62
What are the enzymes involved in the attachment of ubiquitin to proteins?
→ E1: activating enzyme → E2: ligase → E3: transferase
63
Which enzyme of ubiquitin catalyzes the transfer of ubiquitin to the ε-amino group of a lysyl residue of the target protein?
E3
64
The ligase-catalyzed attachment of four or more additional ubiquitin molecules happens at lysyl residues ____
63 and 48
65
Amino terminal _______ residues retard, whereas ______ accelerate ubiquitination
Met or Ser - retard | Asp or Arg - accelerate
66
``` Which of the following is a result of defects in ubiquitination? EXCEPT: A. Angelman Syndrome B. congenital polycythemia C. von Hippel-Lindau syndrome D. AD juvenile PD ```
D. Angelman syndrome, autosomal recessive (AR) juvenile Parkinson’s disease, von Hippel-Lindau syndrome, and congenital polycythemia.
67
This consists of a macromolecular, cylindrical complex of proteins, whose stacked rings form a central core that harbors the active sites of proteolytic enzymes.
proteasome
68
What are the organs involved in the production of the proteolytic enzymes?
Stomach Pancreas Small intestine
69
What cells of the stomach secrete HCl?
Parietal cells
70
Which cells of the stomach secretes pepsinogen?
Chief cells
71
Trypsin cleaves only when the carbonyl group of the peptide bond is contributed by _______
arginine or lysine Tryp mo si RK
72
What enzyme activates trypsinogen and what cells secrete it?
Enteropeptidase secreted by duodenal epithelial cells
73
Which protease is the common activator of all zymogen?
Trypsin
74
Which 2 polypeptide hormones of the digestive tract mediates zymogen?
Cholecystokinin and Secretin
75
Which amino acids are hydrolyzed by Chymotrypsin?
Thr, Tyr, Phe, Leu, Met Chyamo To Top PLM?
76
Which amino acids are hydrolyzed by Elastase?
Glycine, Alanine, Serine Elas GAS
77
Which amino acids are hydrolyzed by Carboxypeptidase A?
Val, Ala, Iso, Leu Carboxypeptidase A is VAIL
78
Which amino acids are hydrolyzed by Carboxypeptidase B?
Arg, Lys B the same with Trypsin
79
This is an exopeptidase that repeatedly cleaves the N-terminal residue from oligopeptides to produce even smaller peptides and free amino acids. In which organ is it found?
Aminopeptidase = small intestine
80
Di- and tripeptides are taken up by a ________ and are hydrolyzed in the cytosol to amino acids
proton-linked peptide transporter (PepT1)
81
Amino acids from oligopeptides go straight to which organ?
liver
82
Branched-chain amino acids are NOT metabolized by the liver, but instead sent from the liver to ______ via blood (direct)
muscle
83
In the kidneys, __________ diseases are secondary to defective transport systems for AA
congenital tubular
84
Which amino acids are not reabsorbed in Cystinuria apart from cysteine?
Dibasic amino acids: | Ornithine, Citrulline and Arginine
85
This is a rare defect in the transport of cystine out of lysosomes that results in the formation of cystine crystals within the lysosome and widespread tissue damage
Cystinosis
86
Branched-chain amino acids, particularly ______ are released by muscles and taken up by brain
valine
87
This organ is the site of the urea cycle enzymes necessary for disposal of excess nitrogen
Liver
88
Which AA serves as source of ammonia for excretion by the kidney?
Glutamine
89
Which organ provides a major source of serine for uptake by peripheral tissues, including liver and muscle?
Kidney
90
The rate of hepatic gluconeogenesis from which amino acid is far higher than from all other amino acids?
alanine
91
Which amino acids provide the brain with an energy source in the fasting state, and are extracted predominantly by muscle postprandially, having been spared by the liver?
Branched-chain amino acids
92
Which organs release amino acids?
Stomach, Intestine, Spleen, Pancreas
93
Fish are considered as ______ as they excrete alpha-amino acid as highly toxic ammonia
Ammonotelic
94
Birds are considered as _____ as they excrete alpha-amino acid as nitrogen-rich uric acid
Uricotelic
95
Humans are considered as ____ as they excrete alpha-amino acid as nontoxic, highly water-soluble urea
Ureotelic
96
What are the stages of Biosynthesis of Urea?
1. Transamination 2. Oxidative deamination of Glutamate 3. Ammonia Transport 4. Reactions of Urea Cycle
97
What are the AA that don't participate in transamination?
K, T, P, hydroxyP
98
Removal of _________ is an obligatory step in the catabolism of all amino acids
amino group
99
What is the usual acceptor of amino group during transamination in urea synthesis?
α-ketoglutarate
100
Which enzyme is the exception to the rule that aminotransferases funnel amino groups to form glutamate?
Aspartate aminotransferase
101
Where does AST take amino group from to form the source of nitrogen in the urea cycle?
Glutamate
102
Where does AST transfer the amino group to form the source of nitrogen in the urea cycle?
OAA
103
What is generated when aminotransferase transfers amino group of an amino acid to the pyridoxal part of the coenzyme?
Pyridoxamine phosphate
104
Which laboratory transaminase is more sensitive?
AST
105
Which laboratory transaminase is more specific?
ALT
106
How can ALT and AST manifest in non-hepatic diseases?
Low ALT and Hight AST
107
What enzyme is used in the oxidative deamination step of Urea synthesis?
Glutamate dehydrogenase
108
The action of glutaminase is similar to the reaction catalyzed by which enzyme?
L-asparaginase
109
Which enzymes catalyze the interconversion of free ammonium ions and glutamine?
glutamine synthetase and glutaminase
110
What are the 2 sources of nitrogen for UREA?
Ammonium and Aspartate
111
What is the source of carbon and oxygen for Urea Synthesis?
CO2
112
Which requirement in Urea synthesis is consumed in reaction 2 and regenerated in reaction 5?
Ornithine

BIOCHEMISTRY S02 (2 decks)

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