Week 9 Metabolism Of The Carbon Skelteton Flashcards

1
Q

WHAT IS THE CARBON SKELETON

A

Carbon skeleton
α-keto acids (different kinds – depends on the side chain)
Converted into metabolic intermediates:
• Acetyl-CoA
• Acetoacetyl-CoA
• Pyruvate
• Krebs cycle intermediates
Source of energy

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2
Q

SUMMARY OF AMINO ACID METABOLISM

A

The catabolic pathways of each amino acid are different, but they converge on only six compounds.
For some amino acids different parts of the carbon skeleton are used to make different compounds.
Amino acids are glucogenic or ketogenic (or both).
• Glucogenic AA’s can be used to make glucose via gluconeogenesis
• Ketogenic AA’s can be used to make acetyl-CoA

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3
Q

REACTIONS IN AMINO ACID CATABOLISM: 1-CARBON TRANSFERS

A

Different coenzymes involved in transferring a carbon from amino acid substrates:

Biotin transfers carbon as CO2 (highly oxidised). Involved in removal of o2

S-Adenosylmethionine transfers carbon as -CH3 (highly reduced). Transfer carbon alongside hydrogen

Tetrahydrofolate transfers carbon in several oxidation states. Break down all other amino acids that aren’t highly oxidised or reduced
• Note: The oxidised form of tetrahydrofolate is folate (folic
acid), which is vitamin B9.

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4
Q

PLP CAN ACT AS A COFACTOR IN SOME 1-C TRANSFER REACTIONS

A

PLP = can also be used in one carbon metabolism, able to remove co2 from different compounds

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5
Q

CATABOLISM OF SIX AMINO ACIDS CONVERGES ON PYRUVATE

A
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6
Q

CATABOLISM OF SEVEN AMINO ACIDS CONVERGES ON ACETYL-COA

A

The catabolism of tryptophan is the most complex of all the amino acids.
Some parts of the molecule are used in the biosynthesis of other important compounds.

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7
Q

CATABOLISM OF FIVE AMINO ACIDS CONVERGES ON A-KETOGLUTERATE

A
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8
Q

CATABOLISM OF FOUR AMINO ACIDS CONVERGES ON SUCCINYL-COA

A
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9
Q

ASPARAGINE AND ASPARTATE ARE OXIDISED TO OXALOACETATE

A

Asna>Asp is a deamination reaction catalysed by asparaginase.
Asp>aoxaloacetate is achieved through transamination, with α-ketoglutarate being aminated to glutamate at the same time.
In mammals oxaloacetate is converted to malate then transported into the mitochondria, where it can enter the citric acid cycle.

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