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Advanced Metabolism > Week 5 > Flashcards

Week 5 Flashcards

1
Q

Glutamate can be made from which three amino acids?

A

Glutamine
Proline
Arginine

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2
Q

Which amino acid contributes to the structure of fibrous proteins like collagen?

A

Proline

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3
Q

Which two amino acids are both glucogenic and ketogenic?

A

Threonine and tyrosine

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4
Q

What are the 3 circumstances as to which amino acids undergo catabolism?

A
  • normal synthesis and degradation of cellular proteins
  • dietary protein surplus
  • during starvation or in uncontrolled diabetes mellitus
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5
Q

Which amino acids are sent to the muscles?

A

Branched chain AA

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6
Q

What is the first step of AA degradation?

A

The alpha amino group is separated from the carbon skeleton and shunted into the pathways of amino acid metabolism

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7
Q

What is the first step of AA degradation catalysed by?

A

Aminotransferases

Transaminases

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8
Q

What and where do dietary amino acids collect as/where?

A
  • collect as glutamate

- reaching the liver

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9
Q

What are the two general collection points for aa from the tissues?

A

Alanine and glutamine

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10
Q

What are the two general collection points for amino groups in the liver?

A

Glutamate and glutamine

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11
Q

Where are most amino acids metabolised?

A

In the liver

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12
Q

What are the four amino acids which are extremely important in nitrogen metabolism?

A
  • glutamate
  • glutamine
  • alanine
  • aspartate
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13
Q

In skeletal muscle excess amino groups are transferred to pyruvate to make ?

A

Alanine (alanine cycle)

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14
Q

Which amino acid has an important role once the AA reach the liver?

A

Aspartate

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15
Q

Which prosthetic group do all aminotranferases use?

A

PLP, derived from Vit B6.

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16
Q

Where does the nitrogen removal by transamination occur?

A

Cytosol of the liver

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17
Q

An increased plasma levels of ALT and AST indicates?

A

Damage to cells rich in these enzymes

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18
Q

In the transamination of AA in the form of glutamate which free amino acids can be used to enter the TCA Cycle?

A

All free amino acids except threonine and lysine

alpha keto acids can enter the TCA cycle

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19
Q

The aldehyde form of pyridoxal phosphate can react reversibly with?

A

Amino groups

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20
Q

The aminated form of Pyridoxamine phosphate can react reversibly with?

A

Carbonyl groups

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21
Q

Pyridoxal phosphate is covalently linked to the enzyme via?

A

The active site lysine side chain

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22
Q

After dehydration of the pyridoxal phosphate, what type of base linkage is formed? What is the covalent complex called?

A

A Schiff base linkage.

Internal aldimine

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23
Q

Which oxidase enzyme produces ammonia and alpha keto acid directly? and what cofactor does it use? (primary form of deamination
)

A

L-amino acid oxidase

FMN

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24
Q

What is an example of a secondary means of deamination possible for only hydroxyl amino acids (serine and threonine)?

A

Through the use of a dehydratase mechanism, to form the keto acid and ammonia
- unstable, imine intermediate which hydrolysis spontaneously to yield an alpha keto acid and ammonia.

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25
Q

Which amino acids are the exception to entering the TCA cycle?

A

Leucine and Lysine

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26
Q

Once amino acids are collected as glutamate in the liver, what happens to them?

A

Glutamate undergoes oxidative deamination to release its amino group as ammonia

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27
Q

What is enzyme involved in oxidative deamination of glutamate?

A

Glutamate dehydrogenase
Redox + hydrolysis - transamination
- only occurs in the liver/kidney (mito) and it is the only enzyme that can use either NAD or NADP as a coenzyme

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28
Q

The combined actions of aminotransferases and glutamate dehydrogenase can be either ?

A

Anabolic or catabolic as the equilibrium constant = 1

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29
Q

How is ammonia transported in the bloodstream?

A

Glutamine
Which is catalysed by glutamine synthetase
Ammonia is then liberated in the mitochondria by the enzyme glutaminase

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30
Q

What is the primary regulatory point in nitrogen metabolism?

A

Glutamine synthetase

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31
Q

How is glutamine synthetase regulated?

A
  • Allosteric regulation
  • Covalent post translational modification
  • cumulatative feedback inhibition
  • multiple inhibitors are additive
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32
Q

What donates ammonia to pyruvate in the glucose-alanine cycle to make alanine which in the liver, the ammonia can be removed and the pyruvate can be used to make gluconeogenesis.

A

Glutamate

The energetic burden is on the liver rather than the muscle

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33
Q

Which enzyme is used in the glucose alanine cycle?

A

Alanine aminotransferase

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34
Q

In the liver what are amino acids transferred to to form glutamate?

A

Alpha ketoglutarate

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35
Q

In the liver, glutamine is converted to glutamate by what?

A

Glutaminase - releasing nitrogen

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36
Q

In the liver, glutamate is reduced to ketoglutarate by what?

A

Glutamate dehydrogenase

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37
Q

Alanine releases its nitrogen by ?

A

Alanine aminotransfersae

38
Q

In skeletal muscle excess amino groups are transferred to pyruvate to form ?

39
Q

What are the requirements of the urea cycle?

A
  • one free ammonia and one nitrogen in aspartate

- the carbon and oxygen are derived from CO2 as bicarbonate

40
Q

Where is urea produced and where does it transport to for excretion?

A

Produced in the liver and is then transported in the blood to the kidneys for excretion in urine

41
Q

Where does the urea cycle begin and then move to?

A

Begins in the liver mitochondria and then moves to the cytosol

42
Q

Glutamate imported into the mitochondrial matrix is metabolised by glutamate dehydrogenase to produce ammonia and is used to make?

A

Urea cycle precursor Carbamoyl Phosphate

43
Q

Excess glutamate is metabolised in the … of hepatocytes?

44
Q

What is the urea cycle?

A

The conversion of ammonia to urea

45
Q

How many carbamoyl phosphate synthetases are there?

A
  • mito (aa catabolism)

- cytosolic (nucleotide pyridimine base biosynthesis)

46
Q

How is CPS I regulated?

A

Allosterically, by the enzyme N-acetylglutamate

47
Q

Ornithine and citrulline are … and move across the mito membrane via ….

A

dibasic amino acids

Co transporter

48
Q

Cleavage of argininosuccinate produces?

A

Arginine - the immediate pre cursor of urea

Fumarate

49
Q

Fumarate can be hydrated to form? oxidised to form? transaminated to form?

A

Malate
Oxaloacetate –> TCA (glucose production)
Aspartate

50
Q

In the reaction of malate being oxidised to oxaloacetate what is being reduced and oxaloacetate is being continually removed by the highly exergonic ….

A

NAD is reduced to NADH and H

Citrate Synthase Reaction

51
Q

How can arginosuccinate be made?

A

Aspartate and citrulline

52
Q

Where does the cleavage of arginine to urea happen?

A

In the liver

53
Q

In the final step of the urea cycle arginase cleaves urea from arginine by the addition of …., regenerating cytosolic ……

A

H2O

Ornithine

54
Q

In patients with kidney failure, plasma levels of urea are …?

55
Q

In the GI tract, urea is cleaved by bacteria with the enzyme …, releasing ….

A

Urease

NH4

56
Q

Intestinal urease activity can contribute to hyperammonemia in patients with ….

A

Kidney failure

57
Q

What is a diagnostic tool for H.Pylori?

A

Breath test

- radiolabelled isotope

58
Q

What are the 5 sources of ammonia?

A
  • transamination by aminotransferases and oxidative deamination by glutamate dehydrogenase
  • non toxic transport of glutamine by action of glutamine synthetase and glutaminase
  • bacterial action of urease in intestine
  • digestion/degradation of amines from diet or hormones/neurotransmitters by amine oxidase
  • catabolism of purine and pyrimidines
59
Q

In the urea cycle which two amino acids move between the hep mito and cyto?

A

Ornitihine and citrulline

60
Q

Nitric oxide and urea have in common the fact that they both have … as an immediate precursor?

61
Q

Ammonia is transported in the blood from extrahepatic organs as which ?

A

Alanine and glutamine

62
Q

Alanine catabolism in the liver results in pyruvate production which can be incorporated into which molecule for return to the muscle?

63
Q

In the muscle name two other amino acids that can regenerate pyruvate?

A

Isoleucine and valine

64
Q

In Hyperammonemia, serum levels can rise above?

A

1,000umol/L

Leading to neurotoxin defects

65
Q

What are the two enzyme deficiencies that have effects in the mito?

66
Q

What are the three enzyme deficiences that have effects in the cyto?

67
Q

What are the the three transporter defects in the urea cycle?

A
  • ornithine carrier
  • aspartate/glutamate carrier
  • dibasic amino acid carrier
68
Q

What two aromatic acids can be used to combine glycine and glutamine which can be used in the treatment for deficiencies in the urea cycle?

A

Benzoate and phenylbutyrate - removes ammonia

69
Q

What are three cofactors involved in the transfer of carbon in amino acid metabolism?

A
  • biotin
  • tetrahydrofolate
  • S-adenosylmethionine (SAM)
70
Q

What are the common type of transfers in amino acid metabolism?

A

One Carbon transfers

71
Q

Which folate can transfer carbon in different oxidation states?

A

Tetrahydrofolate

72
Q

Which enzyme is involved in the carbon group transfer to which tetrahydrofolate donates the carbon for the synthesis and degradation of glycine?

A

Serine hydroxymethyl transferase + cofactor THF

73
Q

What form does biotin transfer carbon as?

A

Biotin transfers carbon in its most oxidised form as CO2

Biotin Dependent Carboxylations

74
Q

SAM transfers one carbon to? (The most preferred co-factor for many biological reactions)

A

Methyl groups only

In the most reduced form

75
Q

How is SAM synthesised?

A
  • methionine
  • ATP
  • Methionine adenosyl transferase
76
Q

What is required for the conversion of norepinephrine to epinephrine?

77
Q

Which carbon skeletons breakdown to fumarate?

A

Phenylanine

Tyrosine

78
Q

Which carbon skeletons breakdown to succinyl CoA?

A

Met, Ile, Thr and Val

79
Q

Glycine is degraded by three different pathways?

A
  • oxidative cleavage
  • converted to serine
  • glycine converted to glyoxylate by D-amino acid oxidase
80
Q

Glycine is converted pyruvate via conversion of glycine to serine by ?

A

Serine hydroxymethyltransferase

81
Q

Nonketotic hyperglycinemia is caused by a defect in ?

A

The glycine cleavage enzyme activity

  • high levels of serum glycine
  • leads to severe mental deficiency and death in early childhood
82
Q

Oxalate crystals can form … and if in excess is called?

A

kidney stones

Urolithiasis

83
Q

A defect in phenylanine hydroxylase results in ?

A

PKU leading to elevated levels of phenylaline

84
Q

Phenylalanine can be converted to tyrosine, which can produce?

A
  • Tissue Proteins
  • Melanin
  • Catecholamines
  • Fumarate and Acetoacetate
85
Q

What is the disorder that causes urine to turn black?

A

Alkaptonuria

86
Q

What are the three characteristic symptoms of Alkaptonuria?

A
  • homogentisic aciduria
  • Excess homogentisic acid
  • Arthiritis
    Appear after 30
87
Q

What is the treatment for alkaptonuria?

A

Diet low in phenylalaine and tyrosine

88
Q

Tyrosine is oxidised by what enzyme?

A

Tyrosine Hydroxylase

89
Q

Tyrosine is the precursor for which pigment molecules?

90
Q

Albinism is a result of ?

A

Defect in tyrosine metabolism… less melanin

enzyme: tyrosinase

91
Q

Any defect in the pathway through tyrosine to acetoacetyl coA results in ?

A

Disease State

Advanced Metabolism (8 decks)

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