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Biochem Take 2. > Amino Acids: Metabolism of Carbon Skeletons. > Flashcards

Amino Acids: Metabolism of Carbon Skeletons. Flashcards

1
Q

What is pyridoxial phosphate also known as?

A

Vitamin B6.

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2
Q

What is an essential amino acid?

A

An amino acid that must be obtained through the diet as the body cannot make it.

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3
Q

What is a non essential amino acid?

A

An amino acid that can be synthesised by the body.

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4
Q

The bodys pool of amino acid is topped up by what processes?

A

Amino acids from protein turnover.

Amino acids from dietary proteins.

Non-essential amino acids that are synthesised by the body.

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5
Q

The amino acids in the body’s amino acid pool can be used for what processes?

A

Protein synthesis.

The synthesis of specialised products.

Amino acid catabolism.

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6
Q

Amino acid catabolism leads to what?

A

The release of ammonia in urea.

The release of carbon skeletons.

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7
Q

The carbon skeletons that are released by the catabolism of amino acids can be used for what processes?

A

Making glucose.

Making ketone bodies.

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8
Q

Are excess amino acids ever stored in the body?

A

No.

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9
Q

How many amino acids does the body need?

A

20.

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10
Q

What stereoisomer of amino acids will the body use?

A

Always the L form.

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11
Q

How many of the 20 amino acids are essential?

A

10.

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12
Q

How many of the 20 amino acids are non-essential?

A

10.

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13
Q

Cant the carbon skeleton be used to classify amino acids?

A

Yes.

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14
Q

What are the 2 classifications of amino acids by their carbon skeletons?

A

Glucogenic amino acids.

Ketogenic amino acids.

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15
Q

What does the catabolism of glucogenic amino acids yield?

A

Carbon skeletons that form pyruvate or intermediates of the TCA cycle.

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16
Q

The carbon skeletons of glucogenic amino acids can be used as what precursors?

A

As gluconeogenic precursors.

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17
Q

The catabolism of ketogenic amino acids will yield what?

A

A carbon backbone that forms acetoacetate, ACoA or acetoacetyl CoA.

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18
Q

The carbon skeletons of ketogenic amino acids can be converted to what?

A

To fatty acids and ketone bodies.

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19
Q

Can ketogenic amino acids be converted to glucose?

A

No.

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20
Q

What are the 10 essential amino acids?

A

PVT TIM HALL.

Phenylalanine.
Valine.
Tryptophan.

Threonine.
Isoleucine.
Methionine.

Histidine.
Arginine.
Lysine.
Leucine.

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21
Q

Which essential amino acid is essential in children?

A

Arginine.

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22
Q

Why is arginine only essential in children?

A

As it is made in the urea cycle which is more active in adults than in children.

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23
Q

What are the 10 non-essential amino acids?

A

AGA CAPS GAG.

Asparagine.
Glycine.
Aspartate.

Cysteine.
Arginine.
Proline.
Serine.

Glutamine.
Alanine.
Glutamate.

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24
Q

Does every amino acid give a corresponding keto acid?

A

Yes.

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25
Q

What is the keto acid of alanine?

A

Pyruvate.

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26
Q

What is the keto acid of glutamate?

A

Alpha ketogluterate.

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27
Q

What is the keto acid of aspartate?

A

Oxaloacetate.

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28
Q

What 2 amino acids are always keto acids?

A

Leucine.

Lysine.

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29
Q

What are the 15 glucogenic amino acids?

A

PATHS GAG CAMP GAV.

Proline. 
Aspartate.
Threonine.
Histidine.
Serine.

Glycine.
Arginine.
Glutamine.

Cysteine.
Alanine.
Methionine.
Proline.

Glutamate.
Asparagine.
Valine.

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30
Q

What are the 5 amino acids that are both glucogenic and ketogenic?

A

TIP TT.

Tyrosine.
Isoleucine.
Phenylalanine.

Tryptophan.
Threonine.

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31
Q

What can the carbon skeletons of glucogenic and ketogenic amino acids yield?

A

ACoA or fumarate.

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32
Q

What does the catabolism of amino acids involve?

A

The removal of the amino group from the amino acid and then breaking down the carbon skeleton.

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33
Q

What are the glucogenic products of amino acid catabolism?

A

SOAP F.

Succinyl CoA.
Oxaloacetate.
Alpha ketogluterate.
Pyruvate.

Fumarate.

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34
Q

What are the ketogenic products of amino acid catabolism?

A

AA.

Acetyl CoA.
Acetoacetyl CoA.

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35
Q

Which 2 amino acids form oxaloacetate?

A

Asparagine (ASN).

Aspartate.

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36
Q

How does asparagine form oxaloacetate?

A

It is hydrolysed by asparaginase to give NH3 and aspartate.

Aspartate gives OAA after transamination by aminotransferase (AST).

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37
Q

What 4 amino acids form alpha keto-gluterate?

A

GAPH.

Glutamate.
Arginine.
Proline.
Histidine.

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38
Q

What 5 amino acids form pyruvate?

A

G CATS.

Glycine.
Cysteine.
Alanine. 
Threonine.
Serine.
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39
Q

What glycolytic intermediate can serine be made from?

A

2-phosphoglycerate.

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40
Q

What process can be used to form pyruvate from alanine?

A

Transamination by ALT.

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41
Q

Which amino acids can form fumarate?

A

TP.

Tyrosine.
Phenylalanine.

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42
Q

The amino acids that can form fumarate can also form what?

A

Acetoacetate.

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43
Q

Which 4 amino acids for succinyl CoA?

A

V TIM.

Valine.

Threonine.
Isoleucine.
Methionine.

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44
Q

Is methionine a ketogenic or glucogenic amino acid?

A

Both.

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45
Q

Which amino acids from ACoA or acetoacetyl CoA?

A

LILT.

Leucine.

Isoleucine.

Lysine.

Tryptophan.

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46
Q

What molecule will leucines ketoacid form?

A

Acetoacetate as it is strictly ketogenic.

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47
Q

What molecule will isoleucines ketoacid form?

A

Acetyl CoA, also known as propionyl CoA.

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48
Q

What molecule will lysines ketoacid form?

A

ACoA as it is strictly ketogenic.

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49
Q

What molecule will tryptophans ketoacid form?

A

ACoA.

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50
Q

Which amino acids can form acetoacetate and fumarate during their catabolism?

A

Tyrosine and phenylalanine.

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51
Q

Which essential amino acid is required for the synthesis of all proteins within the body?

A

Methionine.

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52
Q

Which amino acid is used as a pre-cursor to make cysteine?

A

Methionine.

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53
Q

What is step 1 of the metabolism of methionine?

A

Dietary methionine will be added to an adenosine group from an ATP molecule to form S-adenosylmethionine (SAM).

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54
Q

What enzyme is used in step 1 of the metabolism of methionine?

A

S-adenosylmethionine synthase.

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55
Q

Why is S-adenosylmethionine (SAM) a very important molecule in biological reactions?

A

As it can donate its methyl group to form many methylated products.

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56
Q

What is step 2 of the metabolism of methionine after SAM has been formed?

A

The methyl group is removed from SAM forming the molecule S-adenosylhomocysteine (SAH).

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57
Q

What enzyme removes the methyl group from SAM in step 2 of the metabolism of methionine?

A

Various methyltransferases.

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58
Q

What is step 2 of the metabolism of methionine after SAH has been formed?

A

The adenosine group is removed from adenosylhomocysteine to form homocysteine.

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59
Q

What enzyme removes the adenosine group in step 3 of the metabolism of methionine?

A

Adenosylhomocysteinase.

60
Q

Why is homocysteine an important molecule?

A

It can be used in a number of pathways or it can be used to re-synthesise methionine.

61
Q

What enzyme is used to re-synthesise methionine from homocysteine?

A

Methionine synthase.

62
Q

What coenzymes are used with methionine synthase to re-synthesise methionine?

A

Methyltetrahydrofolate and methyl B-12.

63
Q

What do the co enzymes do when methionine synthase is re-synthesising methionine?

A

They are responsible for carrying the methyl group that is replaced onto homocysteine to make methionine.

64
Q

What does a deficiency in B12 or methyltetrahydrofolate (folic acid) result in?

A

In an accumulation of homocysteine in the bloodstream and in the urine.

65
Q

Where does the methyl group that is transferred onto homocysteine in the re-synthesis of methionine taken from?

A

From methyltetrahydrofolate (folic acid).

66
Q

What happens in step 4 of the metabolism of methionine, once homocysteine has been formed?

A

Homocysteine is combined with serine to make cystathionine.

67
Q

What enzyme is used to combine homocysteine with serine in step 4 of the metabolism of methionine?

A

Cystathionine β-synthase.

68
Q

What co-enzymes does cystathionine β-synthase use in step 4 of the metabolism of methionine?

A

Vitamin B6.

69
Q

What happens in step 5 of the metabolism of methionine, once cystathione has been formed?

A

Cystathionine is broken down to form L-cysteine.

70
Q

What enzyme is used to break down cystathione in step 5 of the metabolism of methionine?

A

Cystathionase

71
Q

What co-enzymes are used by cystathionase to break down cystathione in step 5 of the metabolism of methionine?

A

Vitamin B6.

72
Q

What 2 enzymes and coenzymes required for the final 2 steps of the formation of cysteine from methionine?

A

Cystathionine β-synthase. Vitamin B6.

Cystathionase. Vitamin B6.

73
Q

What enzyme and coenzymes are required for the formation of methionine from homocysteine?

A

Methionine synthase. Methyltetrahydrofolate (folic acid) and methyl B-12.

74
Q

What is a tyrosinase deficiency?

A

An inherited deficiency in tyrosinase resulting in the inability to make melanin which results in albinism.

75
Q

What is a homogentisate oxidase deficiency?

A

An inherited deficiency in homogentisate oxidase which leads to alcaptonuria.

76
Q

What is a phenylalanine hydroxylase deficiency?

A

An inherited deficiency in phenylalanine hydroxylase that results in phenyl-ketone urea (PKU).

77
Q

What is phenylalanine hydroxylase responsible for?

A

Making tyrosine from phenylalanine.

78
Q

How many types of phenyl-ketone urea syndrome?

A

2.

79
Q

What are the 2 types of phenyl-ketone urea syndrome?

A

Classic PKU.

Malignant PKU.

80
Q

What deficiency will result in classic PKU syndrome?

A

A deficiency in phenylalanine hydroxylase.

81
Q

What deficiency will result in malignant PKU syndrome?

A

A deficiency in the co-enzyme for phenylalanine hydroxylase or in the enzyme that makes the co-enzyme.

82
Q

What is the co-enzyme for phenylalanine hydroxylase?

A

Dihydrobiopterin (BH4).

83
Q

What makes the coenzyme for phenylalanine hydroxylase (BH4)?

A

Dihydropterin reductase.

84
Q

What can amino acid will not be synthesised as a result of PKU syndrome?

A

Tyrosine.

85
Q

PKU syndrome means that anything that needs to be made from which amino acid cannot be made?

A

Tyrosine.

86
Q

What is one of the most common deficiencies in amino acid metabolism?

A

A PKU disorder.

87
Q

What enzymes normally produce tyrosine from phenylalanine?

A

Phenylalanine hydroxylase.

88
Q

An inability to make tyrosine from phenylalanine will result in what?

A

A build up of phenylalanine which must be converted to phenyl pyruvate and this leads to health problems.

89
Q

What is one of the major outcomes of an untreated PKU disorder?

A

Mental retardation in infants and improper development.

90
Q

A deficiency in vitamin B12 results in what?

A

An accumulation of homocysteine meaning that THF is trapped in its methyl-THF form.

91
Q

Why will a vitamin B-12 deficiency result in THF being trapped in its methyl form?

A

Because THF donates its methyl group to vitamin B-12 to pass on to homocysteine to re-form methionine.

92
Q

What happens to THF once it has donated its methyl group to homocysteine?

A

It can use a variety of carbon sources to replace it, allowing THF to take up many forms.

This allows THF to play a key role in many biological processes such as nucleic acid metabolism and amino acid metabolism.

93
Q

A B12 deficiency prevents THF from donating what?

A

Its methyl group, meaning that THF is stuck in the methyl form.

94
Q

What is homocysteinemia?

A

An inherited enzyme deficiency of cystathione synthase or homocysteine N-methyl transferase.

95
Q

What are the symptoms of homocysteinemia?

A

Lens dislocation after the age of 3 as well as other ocular abnormalities.

Children will also develop osteoporosis and mental retardation.

96
Q

How can homocysteinemia be acquired?

A

As a result of a vitamin B12 deficiency.

97
Q

What is an α-keto acid dehydrogenase deficiency?

A

A deficiency in the enzyme, branched chain α-keto acid dehydrogenase which some amino acids require for their metabolism.

98
Q

Which amino acids require the enzyme, branched chain α-keto acid dehydrogenase for their metabolism?

A

Leucine.

Isoleucine.

Valine

99
Q

A deficiency in branched chain α-keto acid dehydrogenase results in what?

A

A condition called maple syrup urinary disease (MSUD).

100
Q

What are the symptoms of maple syrup urinary disease (MSUD)?

A

Urine that smells like maple syrup due to the accumulation of amino acids that cannot be metabolised.

101
Q

What are the 4 co-enzymes required by branched chain α-keto acid dehydrogenase?

A

FAD.

NAD.

Lipoic acid.

Thiamine CoA.

102
Q

The biosynthesis of non-essential amino acids is often the reverse of what process?

A

The reverse of their degradation.

103
Q

What is alanines carbon skeleton and how does it form it?

A

Carbon skeleton. Pyruvate.

Formation. Transamination of precursor via ALT.

104
Q

What is arginines carbon skeleton and how does it form it?

A

Carbon skeleton. Orthinine.

Formation. Arginiosuccinate lyase reaction in urea cycle.

105
Q

What is asparagines carbon skeleton and how does it form it?

A

Carbon skeleton. OAA.

Formation. Amide reaction from glutamine.

106
Q

What is aspartates carbon skeleton and how does it form it?

A

Carbon skeleton. OAA.

Formation. Transamination of precursor via AST.

107
Q

What is cysteines carbon skeleton and how does it form it?

A

Carbon skeleton. Serine.

Formation. Sulphur group from methionine.

108
Q

What is glutamates carbon skeleton and how does it form it?

A

Carbon skeleton. Alpha K-G.

Formation. Transamination of precursor.

109
Q

What is glutamines carbon skeleton and how does it form it?

A

Carbon skeleton. Alpha K-G.

Formation. Amide group from free NH4+.

110
Q

What is glyines carbon skeleton and how does it form it?

A

Carbon skeleton. 3-phosphoglycerate.

Formation. From serine via transfer of methylene group.

111
Q

What is prolines carbon skeleton and how does it form it?

A

Carbon skeleton. Glutamate.

Formation. Cyclisation of glutamate semialdehyde.

112
Q

What is serines carbon skeleton and how does it form it?

A

Carbon skeleton. 3-phosphoglycerate.

Formation. Oxidation to keto acid, transamination, hydrolysis of phosphate.

113
Q

What is tryrosines carbon skeleton and how does it form it?

A

Carbon skeleton. Phenylalanine.

Formation. Hydroxylation of phenylalanine by phenylalanine hydroxylase.

114
Q

Which amino acids can only be synthesised when methionine and phenylalanine are available from the die?

A

Tyrosine.

Cysteine.

115
Q

Which 2 amino acids are interconvertible?

A

Glycine.

Serine.

116
Q

What is transferred between glycine and serine to interconvert them?

A

A hydroxymethyl group.

117
Q

What enzyme transfers the hydroxymethyl group between glycine and serine?

A

Hydroxymethyltransferase.

118
Q

How does hydroxymethyltransferase transfer the hydroxymethyl group between glycine and serine?

A

It will take a methyl group from methylene-tetrahydrofolate and transfer it to glycine to form serine or vice versa.

119
Q

How is glutamate produced from histidine?

A

Histidine is deaminated to form N-formiminogluterate (FIGLU) which then donates a formimino group to THF to produce glutamate.

120
Q

The active form of folic acid in the body is called what?

A

Tetrahydrofolate (THF).

121
Q

What enzyme is responsible for activating THF?

A

Dihydrofolate reducatase

122
Q

What co-enzymes does dihydrofolate reducatase require to produce THF?

A

2 NADPH molecules.

123
Q

THF can be thought of as a carrier of what atom?

A

Carbon.

Or carbon containing compounds.

124
Q

The different carbon forms of THF can be used for what?

A

A number of reactions such as the synthesis of purines and pyrimidines that are used to make nucleotides.

125
Q

A deficiency in folic acid can result in what neurological defect?

A

Spina bifida.

126
Q

Can humans make folic acid?

A

No.

It must be obtained from the diet.

127
Q

Can microbes make folic acid?

A

Yes.

128
Q

How is folic acid that is obtained in the diet activated?

A

By an enzyme called dihydrofolate in a 2 step reaction.

129
Q

Why is THF incredibly important in all organisms?

A

It will synthesise important precursors for nucleotides.

130
Q

Why do anticancer drugs inhibit dihydrofolate reductase

A

So that purines and pyrimidine synthesis stops, this prevents the cancer cells from obtaining them and slows cell division.

131
Q

How do microorganisms make folate?

A

They can make it from PABA.

132
Q

What family of drugs will inhibit the synthesis of folic acid in microorganisms?

A

Sulphonamides.

133
Q

What enzyme will will sulphonamides inhibit?

A

Dihydropteroate synthetase.

134
Q

B12 is only found in what organisms?

A

Animals.

135
Q

What 2 enzymes require vitamin B12 as a coenzyme?

A

Homocysteine N-methyltransferase (methionine synthase).

Methyl manolyl CoA mutase.

136
Q

Is vitamin B12 required for the re-synthesis of methionine from homocysteine?

A

Yes.

Along with THF.

137
Q

What is methyl manolyl CoA mutase used for?

A

The metabolism of amino acids and odd chain fatty acids.

138
Q

What is the final product of the beta oxidation of odd chain fatty acids?

A

Propionyl CoA.

139
Q

What happens to the propionyl CoA that is produced by the beta oxidation of odd chain fatty acids?

A

It is converted to methyl-malonyl CoA.

140
Q

What enzyme converts propionyl CoA to methyl-malonyl CoA?

A

Propionyl CoA carboxylase.

141
Q

Does propionyl CoA carboxylase require any coenzymes when it converts propionyl CoA to methyl-malonyl CoA?

A

Biotin.

142
Q

What happens to methyl malonyl CoA that is formed from the from the breakdown of odd chain fatty acids?

A

It can is converted to succinyl CoA.

143
Q

What enzyme converts methyl malonyl CoA to succinyl CoA?

A

Methyl manolyl CoA mutase.

144
Q

What coenzyme does methyl manolyl CoA mutase require when it converts malonyl CoA to succinyl CoA?

A

B12.

145
Q

What happens to the succinyl CoA that is produced in the final step of the breakdown of odd chain fatty acids?

A

It is a glucogenic carbon skeleton and enters the TCA cycle.

Biochem Take 2. (24 decks)

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