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Biochemistry PMY-3 > Nitrigen III > Flashcards

Nitrigen III Flashcards

1
Q

Contrast essential and nonessential

A

Dietary essential- cannot be synthesized by the cell(it must be provided by the diet)

Dietary nonessential- can be synthesized by the cell

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2
Q

What are glucogenic amino acids?

A

Catabolism yields Pyruvate (an alpha keto acid) or one of the intermediates of the citric acid cycle
-these are substrates for gluconeogenesis

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3
Q

What are ketogenic amino acids?

A

Yields acetoacetate, Acetyl CoA or acetoacetyl CoA

-these may be substrates for ketones body synthesis

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4
Q

Which amino acids are conditionally dietary essential?

A

Cysteine (Cys)

Tyrosine

Arginine

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5
Q

Why is arginine conditionally essential?

A

Arg is conditionally essential, its biosynthesis May not keep up with a rapidly growing individual
-children who are in positive nitrogen balance

  • gaining protein weight, or muscle mass
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6
Q

Why is tyrosine conditionally essential?

A

Tyrosine is conditionally essential: if Phe is limited in the diet Tyr becomes essential
-Phe has an aromatic ring

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7
Q

Why is Cys conditionally essential?

A

Cys is condition essential: if Met is limited in diet, Cys becomes essential
-Met contains the sulfur

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8
Q

What are the glucogenic nonessential amino acids ?

A
  1. Alanine
  2. Arginine
  3. Asparagine
  4. Aspartate
  5. Cysteine
  6. Glutamate
  7. Glutamine
  8. Glycine
  9. Proline
  10. Serine
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9
Q

What are the glucogenic nonessential amino acids?

A
  1. Histidine
  2. Methionine
  3. Threonine
  4. Valine
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10
Q

What is the glucogenic AND ketogenic nonessential amino acid?

A

Tyrosine

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11
Q

What amino acids are essential Glucogenic AND ketogenic amino acids?

A
  1. Isoleucine
  2. Phenylalanine
  3. Tryptophan
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12
Q

What are the essential ketogenic amino acids?

A

Leucine

Lysine

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13
Q

What are the essential amino acids?

A

PVT TIM HALL

phenylalanine

Valine

Tryptophan

Threonine

Isoleucine

Methionine

Histidine

Arginine

Leucine

Lysine

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14
Q

What are the amino acids that are strictly ketogenic? What does this mean?

A

Lysine and leucine

The degradation of Leu or Lys does not produce a molecule that can support gluconeogenesis

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15
Q

Isoleucine, phenylalanine and tryptophan are ketogenic and Glucogenic, what does this mean?

A

Isoleucine

Phenylalanine

Tryptophan

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16
Q

Why did mammals lose the ability to synthesize all the amino acids?

A
  • warm blooded animals must produce an enormous amount to heat to stay alive
  • Amino acids are part of the diet (calories), so we get all we need from our diet (hopefully)
  • We must eat a lot to survive.
  • With disuse, the pathways were ‘retired’ or lost over time
17
Q

The end products of amino acid catabolism feed into:

A
  1. Glycolytic intermediates
  2. TCA cycle intermediates
  3. Substrate for ketone body
18
Q

What are alpha keto acids? How are they formed?

A

Amino acids are blocked from catabolism by the alpha amino group

  • when the alpha amino group is removed, we call what is left behind the “carbon skeletons “
  • this is an alpha keto acid
19
Q

What 2 ways can cells remove the alpha amino group from an amino acid?

A
  1. Transamination

2. Deamination

20
Q

Describe the amino acceptor/donor in transamination

A

Alpha keto glutarate and glutamate always participate as an amino acceptor/donor pair

21
Q

Describe deamination of the alpha amino group

A

There are many reactions that can deaminate the various amino acids
-we don’t have to be concerned with most of them

For us, the most important deamination reaction is catalyzed by the glutamate dehydrogenase enzyme

  • Reversible enzyme
  • Conversion of Glu to a-KG is oxidative deamination
22
Q

WHat products are formed from amino acid catabolism

A
  1. Pyruvate
  2. Oxaloacetate
  3. a-ketoglutarate
  4. Fumarate
  5. Succinyl CoA
  6. Acetyl CoA (ketogenic)
  7. Acetoacetyl CoA (ketogenic )

The end products of catabolism of phenylalanine and tyrosine are fumarate and acetoacetyl CoA

23
Q

What is the first step of Phe degradation?

A

Phe degraded to tyrosine

Enzyme: phenylalanine hydroxylase

Needs tetrahydrobiopterin and oxygen

Converted to: dihydrobiopterin (BH4)+ H2O

Tyrosine converted to fumarate( glucogenic precursor )

Or acetoacetate (ketone body precursor)

24
Q

When phenylalanine is converted to tyrosine, what can the tyrosine be used for?

A
  • tissue proteins
  • thyroid hormone
  • melanin
  • Catecholamines
  • fumarate
  • acetoacetate
25
Q

What is phenylketonuria?

A

PKU. I (Classic PKU) : deficiency of phenylalanine hydroxylase
-simple enzyme deficiency

  • phenylalanine accumulates
  • tyrosine is deficient
26
Q

How can PKKU be treated ?

A

Individuals who have PKU must be put on a diet restricted for phenylalanine within the first few days after birth

Highlights the importance of newborn screening

27
Q

What Catecholamines can tyrosine be converted to?

A

Hormones, neurotransmitters: dopamine, norepinephrine, epinephrine

28
Q

What causes Alkaptonuria?

A

Deficiency of homogenistic acid oxidase (homogentisate oxidase) causes alkaptonuria

29
Q

What causes tyrosinemia type I?

A

The disease is due to a deficiency in fumaryl-acetoacetate hydrolase

30
Q

What is the last step in tyrosine catabolism?

A

The last step of tyrosine catabolism is cleavage of fumarylacetoacetate

Enzyme: fumarylacetoacetate hydrolase

Products (fumarate which is glucogenic)

Acetoacetate which is ketogenic

31
Q

What is PKU II? What causes it?

A

Malignant PKU/PKU II caused by:

-deficiency of biopterin (BH2) synthesis (any step)

  • deficiency of dihydrobiopterin reductase (inability to convert BH2 —> BH4)
    • cofactors deficiency
    • BH4 is the coenzyme for phenylalanine hydroxylase (and other ring hydroxylation reactions)
    • so BH4 deficiency causes dopamine, norepinephrine, epinephrine (the 3 Catecholamines) and serotonin deficiency
32
Q

How is BH4 formed? What is BH4 used from?

A

BH2 uses NADPH to create BH4+ NADP+ H+

BH4 is required for aromatic ring hydroxylation reactions (formation of serotonin from Trp,L-dopa from Tyr, Tyr from Phe), and some other reactions

33
Q

What is “the catechol “ ?

A
  • has two hydroxyl groups next to each other on an aromatic (arene) ring (benzene ring)
  • So L-Dopa is an amino acid that contains a catechol on its side chain
  • Decarboxylation of L-dopa (CO2 comes off), forms dopamine (a catecholamine)
34
Q

What 3 Catecholamines are formed from the PHE/TYR pathway?

A
  1. Dopamine
  2. Norepinephrine
  3. Epinephrine

Norepinephrine converted to epinephrine by adding methyl group via SAM replacing the norepinephrine NH3

35
Q

How is serotonin formed ?

A

The amino acid tryptophan is hydroxylase on its aromatic ring

Serotonin is derived from the amino acid tryptophan

  • Requires BH4 for ring hydroxylation
  • Serotonin is an amine
  • Important hormone and neurotransmitter

Biochemistry PMY-3 (37 decks)

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