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Biochemistry I > Chapter 32: Amino Acid Catabolism, Disposal of the Carbon Skeleton > Flashcards

Chapter 32: Amino Acid Catabolism, Disposal of the Carbon Skeleton Flashcards

1
Q

Consider amino acids in two halves

A
  • Carbon skeleton

- Amino group

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2
Q

Carbon atoms from amino acids enter metabolic pathways

A
  • After the amino group is removed (first step)
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3
Q

AAs that enter glycolysis or the CAC are called

A
  • Glucogenic amino acids
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4
Q

AAs that are converted to FAs or to the keto acids (acetoacetic acid or acetate) are considered

A
  • Ketogenic amino acids
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5
Q

Thirteen amino acids are

A
  • Purely glucogenic
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6
Q

Only AAs that are purely ketogenic

A
  • Leucine

- Lysine

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7
Q

AAs that are both glucogenic and ketogenic can be metabolized to

A
  • Oxaloacetate

- Acetyl-CoA

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8
Q

Surplus AAs are used as

A
  • Metabolic fuel
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9
Q

Alanine, serine, and cysteine are converted to

A
  • Pyruvate
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10
Q

The carbon skeletons of tryptophan, glycine, and threonine can also be converted to

A
  • Pyruvate
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11
Q

Some of the C5 family (glutamine, proline, arginine, and histidine) are converted to

A
  • Glutamate

- Then alpha-ketoglutarate (via oxidative deamination)

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12
Q

Alpha-ketoglutarate is an intermediate of

A
  • The CAC
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13
Q

Aspartate and asparagine (C4) can both be metabolized to

A
  • Oxaloacetate
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14
Q

Asparagine is hydrolyzed to aspartate by

A
  • L-asparaginase
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15
Q

Aspartate can also be converted to

A
  • Fumarate
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16
Q

Three amino acids are converted to fumarate

A
  • Phenyalanine
  • Tyrosine
  • Aspartate
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17
Q

Phenylalanine and tyrosine are degraded by

A
  • Oxygenases

- Degraded to acetoacetate and ….

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18
Q

In mammals, there is no net mechanism for

A
  • Reconverting acetyl-SCoA or acetoacetyl CoA back to glucose
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19
Q

The keto acids generated from these ketogenic amino acids can be

A
  • Funneled
20
Q

Amino acids that are both glucogenic and ketogenic

A
  • Phenylalanine
  • I
  • T
  • T
  • T
21
Q

Phenylalanine and tyrosine are examples of

A
  • Amino acids that are both glucogenic and ketogenic
22
Q

Metabolism of phenylalanine and other aromatic amino acids follows a common sequence of

A
  • Oxidation
  • Deamination
  • Ring opening hydrolysis
23
Q

Branched-chain amino acids

A
  • Isoleucine
  • Leucine
  • Valine
24
Q

All branched-chain amino acids are

A
  • Essential amino acids
25
Q

BC amino acids are partially degraded by

A
  • Serires of irreversible reactions
26
Q

BC amino acid degradation pathway

A
  1. BC amino acid transaminase
  2. BC a-keto acid dehydrogenase complex
  3. Acyl CoA dehydrogenase
27
Q

BC a-keto acid dehydrogenase complex requires these cofactors

A
  • NAD+
  • FAD
  • Thiamine pyrophopshate
  • Lipoic acid
  • Coenzyme A
28
Q

Which branched chain amino acid is ketogenic or glucogenic?

A
  • Leucine is ketogenic
29
Q

PKU is caused by

A
  • An inborn mutation that leads to aberant splicing
30
Q

In PKU mutation of G is replaced by an A, whic occurs in

A
  • Intron 12
31
Q

In PKU mutation of G is replaced by an A, whic occurs in

A
  • Intron 12
32
Q

Phenylalanine hydroxylase activity measures

A
  • Postnatally
33
Q

When phenylalanine hydroxlase fails to mature,

A
  • Brain damage occurs
34
Q

The disease inherited is an

A
  • Autosomal recessive characteristin

- Frequencey of 1:25,000

35
Q

Phenylalanine acts as an

A
  • Antimetabolite……
36
Q

Tyrosinosis

A
  • Detected in one individual

- Useful in determining correct sequence of reactions ….

37
Q

Alcaptonuria

A
  • Lack of homogentisic acid oxidase

- First of all inborn errors of metabolism to be described

38
Q

Alcaptonuria results in

A
  • Accumulation and elimination of homogentisate in the urine
39
Q

When homogentisate is oxidized upon exposure to the air

A
  • It forms a brownish/black pigment
40
Q

Amino acids can be converted into nonprotein substances

A
  • Hormones
  • Melanin
  • Neurotransmitters
  • Nitrogenous bases
  • Creatine
  • Nitric oxide
  • Heme
41
Q

Hormones from AAs

A
  • Tyrosine > catecholamines (dopamine, epi, norepi) & T3 and T4
42
Q

Melanin can be converted to

A
  • Tyrosine
43
Q

Neurotransmitters from AAs

A
  • Tryptophan > serotonin

- Glutamate > GABA and glutathione

44
Q

Nitrogenous bases from AAs

A
  • Purines & pyrimidines from aspartate & glutamine
45
Q

Creatine from AAs

A
  • Arginine & glycine
46
Q

Nitric acid from AA

A
  • Arginine (urea cycle)
47
Q

Heme from AA

A
  • Glycine

Biochemistry I (34 decks)

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