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Block 3 Week 5 Meg > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

1
Q

Synthesized in bacteria
Reduced form of folate
Transfers single carbon

A

Tetrahydrofolate (THF)

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2
Q

Synthesized from ATP + methionine
Transfers methyl groups
Alter transfer yields SAhcys then hcys

A

SAM

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3
Q

Transfers CO2

A

Biotin

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4
Q

Involved in oxidation reactions

A

Tetrahydrobiopterin

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5
Q

Cofactor in transaminase reaction
Coenzyme form of Vitamin B6
“Holds” the nitrogen

A

Pyridoxal Phosphate (PLP)

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6
Q

Total “ATP” generated from one round of the TCA cycle

A

12 ATP

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7
Q

Citrate inhibits (blank) and is an important component in (blank)

A

glycolysis; FA synthesis

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8
Q

Acetic acid from alcohol metabolism can enter the TCA cycle at this step

A

Acetyl-CoA + OAA –> Citrate

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9
Q

This complex is bound to the inner mitochondrial membrane

A

succinate dehydrogenase

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10
Q

What are methionine and cysteine both derived from?

A

homocysteine

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11
Q

What is tyrosine derived from?

A

phenylalanine

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12
Q

What is the reaction for glutamate synthesis? What enzyme catalyzes this reaction?

A

NH4+ + alpha-KG + NADPH + H+ –> glutamate + NADP+ + H20

Glutamate dehydrogenase

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13
Q

Glutamate synthesis is driven by toxic levels of free (blank). It occurs primarily in the (blank)

A

ammonia; liver

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14
Q

What enzyme takes Glutamate to Glutamine? What is required for this reaction?
What enzyme take Glutamine to Glutamate?
What is produced?

A

Glutamine synthetase
ATP + NH3
Glutaminase
NH4+

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15
Q

Does glutamate transport across cell membranes? Does glutamine?

A

NO; yes

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16
Q

Most abundant circulating amino acid

A

glutamine

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17
Q

(blank) is a Nitrogen donor for many synthesis reactions; (blank) allows transport of the detoxified form of NH4+

A

glutamine; glutamine

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18
Q

Discuss the glucose-glutamine cycle (starts with glucose in the muscle, ends with glucose in the kidney)

A

Glucose-

  • ->alpha-KG (glycolysis/TCA)
  • ->Glutamate (transaminase)
  • ->Glutamine (glutamine synthetase)
  • -> kidney
  • ->Glutamate (glutaminase)
  • ->alpha-KG (glutamate DH)
  • ->glucose (gluconeogenesis)
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19
Q

Equation for alanine synthesis; what enzyme is required for this reaction

A 
AA + pyruvic acid --> alpha-keto acid + alanine
alanine transaminase (ALT)
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20
Q

Transaminases are highly (blank) with a Keq = 1

Transaminases require what cofactor?

A

reversible

PLP

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21
Q

What can be used as a diagnostic for liver damage?

A

Serum ALT levels

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22
Q

Discuss the glucose-alanine cycle

A

In muscle:
Glucose –> pyruvate via glycolysis
Pyruvate –> alanine via alanine aminotransferase
In liver:
Alanine –> pyruvate via alanine aminotranferase
Pyruvate –> glucose via gluconeogenesis

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23
Q

What activates proteolysis of muscle protein to amino acids? Also activates transaminases and gluconeogenesis.

A

Cortisol

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24
Q

Aspartate synthesis; what enzyme is responsible for this reaction?

A

OAA –> ASP
Glutamate –> alpha KG
Glutamate-OAA transaminase (GOT)

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25
Q

Asparagine synthesis; what enzyme is responsible for this reaction?

A

Aspartate –> asparagine
Glutamine + ATP –> Glutamate
asparagine synthetase

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26
Q

Do humans express asparaginase?
Asparagine is often (blank)
Some leukemia cells lack the ability to synthesize (blank)
(blank) injections sometimes used for adult leukemia

A

NO
glycosylated
asparagine
asparaginase

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27
Q

Serine synthesis

A

3 PGA –> SER

Glutamate + NAD+ –> alphaKG + NADH

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28
Q

The formation of serine has (blank) and (blank) intermediates, and generates (blank)

A

phosphopyruvate; phosphoserine; NADH

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29
Q

Glycine synthesis; what enzyme is responsible? What is required for this reaction?

A

Serine –> glycine via serine hydroxymethyltransferase

Requires THF –> N5, N10 methylene THF

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30
Q

Methionine synthesis; 2 things required for this reaction

A

homocysteine –> methionine
Requires B12
Requires Methyl-THF–>THF

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31
Q

Cysteine synthesis

A

Methionine + ATP – > SAM –> SAHcys –> homocysteine –> cystathione –> cysteine + alpha-aminobutyrate

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32
Q

What takes homocysteine to cystathionine? What does this require?

A

cystathionine synthase; PLP

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33
Q

What takes cystathionine to cysteine + alpha-aminobutyrate? What does this require?

A

cystathionase; PLP

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34
Q

What do deficiencies in cystathionine synthase or in cystathionase cause? What is this characterized by? What are treatments?

A

homocystinuria
thinning/lengthening of long bones, osteoporosis, vascular thrombosis, mental deficiency
dietary or vitamin treatments

35
Q

Tyrosine synthesis; what enzyme catalyzes this reaction? What is required?

A

Phenylalanine –> tyrosine via phenylalanine hydroxylase

Requires tetrahydrobiopterine being oxidized to DHB

36
Q

What can tyrosine be taken to via tyrosinase?

A

melanin

37
Q

What can a build up of phenylalanine lead to? Symptoms? What is the treatment for this?

A

PKU; mental retardation, light skin color; dietary, no aspartame

38
Q

Proline synthesis; what is required for this reaction?

A

Glutamate –> Proline

2 NADH –> 2NAD+

39
Q

Ubiquitin binds to (blank) residues on proteins destined for degradation. Ubiquitin can form chains - the (blank) the chain, the higher the signal for degradation.

A

lysine; longer

40
Q

(blank) of protein determines RATE of ubiquination. Destabilizing N-terminal residues (blank) or (blank) = fast ubiquination. Stabilizing N-terminal residues (blank) or (blank) = slow ubiquination.

A

N-terminus
arginine, leucine
methionine, proline

41
Q

(blank) sequences are also targets for degradation

A

P-E-S-T (proline-glutamate-serine-threonine)

42
Q

Disease: formation of protein structures in neurons

A

Alzheimers and Parkinsons

43
Q

Disease: rapid degradation of chloride channels

A

CF

44
Q

Disease: Na+ channel in kidney not degraded, leading to excess Na+ absorption and early-onset hypertension

A

Liddle’s syndrome

45
Q

Amino acids that degrade to pyruvate

A 
Alanine
Cysteine
Glycine
Serine
Threonine
Tryptophan
46
Q

Amino acids that degrade to acetyl-CoA

A

Isoleucine
Leucine
Threoine
Tryptophan

47
Q

defect in phenylalanine hydroxylase

A

PKU

48
Q

defect in Tyrosine aminotransferase

A

tyrosinemia II

49
Q

defect in homogentisate oxidase

A

alkaptonuria

50
Q

defect in fumarylacetoacetate hydroxylase

A

tyrosinemia I

51
Q

Amino acids that degrade to alpha-KG

A 
Arginine
Glutamine
Histidine
Proline
Glutamate
52
Q

Amino acids that degrade to OAA

A

Asparagine

Aspartate

53
Q

Amino acids that degrade to Succinyl-CoA

A

Isoleucine
Methionine
Threonine
Valine

54
Q

Amino acid metabolism: most amino acids go to the (blank). What two amino acids are metabolized in intestinal mucosal cells? What type of amino acids leave the liver to go the muscle to be transaminated before returning to the liver?

A

liver; glutamate/glutamine; branched chain amino acids

55
Q

When fasting, (blank) is a major source of amino acids. (blank) goes to the liver for gluconeogenesis. (blank) goes to kidneys and intestines.

A

muscle tissue; alanine; glutamine

56
Q

List the steps in Phe degradation

A

Phe–>Tyr–>homogentisic acid int.–>fumarylacetoacetate int.–>acetoacetate

57
Q

What enzyme takes Phe –> Tyr

What does a defect in this enzyme cause?

A

Phe hydroxylase; PKU

58
Q

What takes Tyr to its homo intermediate

What does a defect in this enzyme cause?

A

Tyr aminotransferase; tyrosinemia II

59
Q

What takes the homo int. to a fumaryl int? What does a defect in this enzyme cause?

A

homo oxidase; alkaptonuria

60
Q

What enzyme takes fumaryl int to acetoacetate? What does a defect in this enzyme cause?

A

fumaryl hydroxylase; tyrosinemia I

61
Q

What other amino acids degrade to acetyl-CoA?

A

Isoleucine
Lysine
Threonine
Tryptophan

62
Q

To take histadine to Glutamate and ultimately to alpha-KG, how many steps are involved? If there is a defect in histadase (the first step), what does this cause? If there is a folate deficiency, what accumulates?

A

4; histidinemmia; formimino glutamic acid (FIGLU)

63
Q

What other amino acids get degraded to glutamate and ultimately alpha-KG?

A

Arginine
Glutamine
Histadine
Proline

64
Q

What takes serine to cystathione? What takes homocysteine to cystathione? (same enzyme) What does a defect in this enzyme cause?

A

cystathionine synthase; homocystinuria

65
Q

What takes glycine to CO2 and NH4+? What does a defect in this enzyme cause?

A

glycine cleavage enzyme; nonketotic hyperglycinemia

66
Q

What enzyme takes glycine to glyoxylate? What does a defect in this enzyme cause?

A

glycine transaminase; oxaluria type I

67
Q

Discuss the degradation of asparagine to OAA

A

asparagine –> aspartate –> OAA

68
Q

What does a defect in branched chain alpha-keto acid dehydrogenase complex cause?

A

maple syrup urine disease

69
Q

Degradation of (blank) goes through homocysteine, propionyl-CoA, methylmalonyl-CoA, and ultimately Succinyl-CoA. What takes methylmalonyl-CoA to Succinyl-Coa? What does a defect in this enzyme cause?

A

methionine; methyl-malonyl CoA mutase (requires B12); methylmalonic aciduria

70
Q

What other amino acids degrade to succinyl-Coa?

A

Isoleucine
Methionine
Threonine
Valine

71
Q

Missing enzyme Dihydropteridine reductase - causes accumulation of phenylalanine. What does this cause?

A

PKU (non-classical)

72
Q

1st step in urea cycle

A

CO2 + NH4+ –> Carbamoyl phosphate (via Carbamoyl-phosphate synthetase)

73
Q

A build up of carbamoyl phosphate leads to (blank) in urine

A

orotate

74
Q

List the steps of the urea cycle

A 
Carbamoyl phosphate
Citrulline
Arginosuccinate
Arginine
Ornithine
75
Q

How many ATP does the urea cycle require?

A

4 ATP

76
Q

What two intermediates in the cycle are in the mito matrix?

A

ornithine –> citrulline

77
Q

Blood urea level measured as (blank). This rises sharply (uremia) in renal failure

A

BUN

78
Q

Bacterial enzyme (blank) can cleave urea, alkalinizing the urine causing precipitation of magnesium ammonium phosphate -> kidney stones

A

urease

79
Q

Inherited defects of urea cycle enzymes lead to (blank) and encephalopathy. Feeding difficulties, vomiting, lethargy, irritability, aversion to protein rich foods.

(blank) deficiencies because α-ketoglutarate is converted to glutamine.
(blank) levels elevated as well as immediate substrate of deficient enzyme

A

hyperammonemia (lots of NH4+); ATP; glutamine

80
Q 
Therapy for urea cycle enzyme deficiencies:
Limit (blank) intake
Remove excess (blank)
Replace intermediates
Liver transplant
A

protein; ammonia

81
Q

The urea cycle is related to this component of the TCA cycle, and shares argino-succinate as an intermediate

A

aspartate-arginosuccinate shunt

82
Q

Three steps that require a transaminase

A

3PGA –> serine
Pyruvate –> alanine
OAA –> Aspartate

83
Q

Three steps that require NH4+

A

alpha KG –> glutamate
glutamate –> glutamine/proline/arginine
aspartate–>asparagine

Block 3 Week 5 Meg (8 decks)

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