Lecture 31 - AMINO ACIDS AS FUEL MOLECULES Flashcards

1
Q

What is deamination?

A

Removal of an amino group

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2
Q

What does a deamination generate?

A

A carbon skeleton and a free amino group (NH4+)

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3
Q

What can a carbon skeleton be used for?

A

Energy capture (catabolic reactions)

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4
Q

What happens with the free amino group?

A

It is generally excreted

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5
Q

How does deamination occur?

A

Some amino acids release amino groups into solution and some transfer the amino group to a keto acid

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6
Q

What is an example of an amino acid releasing amino group into solution?

A

Glutamate deamination catalysed by glutamate dehydrogenase (GDH)

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7
Q

What are transaminations catalysed by?

A

Amino transferase enzymes (transaminases)

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8
Q

What happens in a transamination?

A

What was the amino acid becomes a keto acid and what was a keto acid becomes an amino acid

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9
Q

What is the coenzyme required for transamination?

A

Pyridoxal phosphate

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10
Q

What is pyridoxal phosphate derived from?

A

Vitamin B6

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11
Q

What does pyridoxal phosphate carry?

A

Amino group from the amino acid to the keto acid

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12
Q

What two forms does pyridoxal phosphate exist in?

A
Pyridoxal phosphate (no amino group)
Pyridoxamine phosphate (with amine group)
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13
Q

What are the steps of a transamination reaction?

A
  1. Amino group is transferred from the amino acid to the pyridoxal phosphate
  2. Amino group is transferred from pyridoxamine phosphate to the keto acid
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14
Q

What are some common amino acid/keto acid pairs?

A

Glutamate <> alpha - ketoglutarate (CAC)
Aspartate <> oxaloacetate (CAC)
Alanine <> Pyruvate (end of glycolysis)

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15
Q

What can be done with keto acids?

A

They can be fed into metabolic pathways

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16
Q

How do keto acids enter metabolic pathways?

A

Some enter directly while others require side chain modification first

17
Q

What are transamination reaction also required for?

A

To remove excess nitrogen by the liver

18
Q

The ammonium ion (NH4+) is ….

A

Toxic in tissues

19
Q

What happens with the toxic ammonium ion?

A

It is removed out of solution an a transamination causes the formation of alanine

20
Q

What happens with alanine?

A

It enters the blood and travels to the liver via the glucose-alanine cycle

21
Q

What happens once alanine is at the liver?

A

A reverse transamination and then deamination regenerate NH4+ to be converted to urea and then excreted