37 Questions
What is a characteristic of essential amino acids?
They must be part of our diet
Why is arginine considered essential during infancy and childhood?
Because of rapid growth and development during this period
What is the term for amino acids that can be synthesized by the human body?
Non-essential amino acids
Which amino acid is a precursor of catecholamines, epinephrine, norepinephrine, dopamine, thyroid hormones, and melanin?
Tyrosine
What is the role of carnitine in the body?
Conversion of fatty acids into energy
What is the product of the condensation of Succinyl CoA and glycine?
Gamma-Aminolevulinic acid
Which amino acid is involved in heme synthesis?
Glycine
What is the cofactor required for the synthesis of Gamma-Aminolevulinic acid?
PLP
What is the relationship between lysine and carnitine?
A deficiency in lysine leads to a deficiency in carnitine
What is the role of alpha-ketoglutarate in amino acid metabolism?
It is converted to glutamine
What is the consequence of deficient glycine or pyridoxine in the diet?
Nutritional anemia
What is the prosthetic group of hemoglobin and myoglobin?
Glycine
What is the component of hemoglobin found in RBCs and myoglobin found in muscles?
Heme
What is the source of carbon skeleton for the synthesis of Glycine, Serine, and Cysteine?
3-Phosphoglycerate
Which citric acid cycle intermediate is involved in the synthesis of Aspartate and Asparagine?
Oxaloacetate
What is the precursor of Tyrosine in the presence of low Phenylalanine?
Phenylalanine
Which amino acid is strictly ketogenic due to its carbon skeleton being converted to Acetyl-CoA or Acetoacetate?
Leucine
How many amino acids have separate catabolic pathways that converge to form the seven intermediate products?
20
What is the precursor of serotonin and melatonin?
Tryptophan
Which amino acid is a precursor of thyroid hormones and melanin?
Tyrosine
What is the role of N-acetyl glutamate in urea synthesis?
It is an allosteric activator of CPS I
What is the precursor of glutathione?
Glutamate, Cysteine, Glycine
What is the precursor of creatine and creatinine?
Arginine, Glycine, Methionine
Which amino acid is a component of the phospholipid involved in cell apoptosis?
Serine
What makes serine nutritionally non-essential amino acid?
It is derived from an amphibolic intermediate
Which one-carbon donor is involved in the reversible conversion of serine to glycine?
SAM
Which of the following amino acids is synthesized from alpha-ketoglutarate?
Glutamine
Which amino acid is the direct precursor of dihydroxyphenylalanine (DOPA)?
Tyrosine
What is the biochemical basis for the characteristic 'musty' odor of the skin and wet diaper in PK, a 3-year-old male?
Elevated levels of phenylacetate
What is the classification of amino acids based on nutrition?
Based on their essentiality or non-essentiality
Which amino acid is involved in the synthesis of creatine?
Glycine
What is the consequence of a deficiency in glutamate metabolism?
Impaired neurotransmission
How do non-essential amino acids differ from essential amino acids?
They can be synthesized by the human body
What is the role of Glycine in porphyrin and heme synthesis?
It is involved in the synthesis of alpha-aminolevulinic acid
What is the primary function of aspartate in the body?
It is involved in the synthesis of glutamate
Which amino acid is involved in the synthesis of methionine?
Homocysteine
What is the role of glycine in the synthesis of creatine?
It is involved in the synthesis of guanidinoacetate
Study Notes
Amino Acid Classification
- Amino acids can be classified into two categories: essential and non-essential.
- Essential amino acids cannot be synthesized by the body and must be part of the diet.
- Non-essential amino acids can be synthesized by the body from amphibolic intermediates of glycolysis, citric acid cycle, and pyruvate.
Essential Amino Acids
- There are 10 essential amino acids: Threonine, Tryptophan, Arginine, Phenylalanine, Lysine, Valine, Histidine, Leucine, Isoleucine, and Methionine.
- These amino acids cannot be synthesized by the body and must be obtained through the diet.
Non-Essential Amino Acids
- There are 10 non-essential amino acids: Alanine, Asparagine, Aspartate, Arginine, Cysteine, Glutamate, Glutamine, Glycine, Proline, and Serine.
- These amino acids can be synthesized by the body from amphibolic intermediates of glycolysis, citric acid cycle, and pyruvate.
Biosynthesis of Non-Essential Amino Acids
- Alanine is synthesized from pyruvate through transamination.
- Glutamine, Proline, and Arginine are synthesized from α-ketoglutarate.
- Glycine, Serine, and Cysteine are synthesized from 3-phosphoglycerate.
- Aspartate and Asparagine are synthesized from oxaloacetate (OAA).
Specialized Products
- Tyrosine is a precursor of catecholamines, epinephrine, norepinephrine, dopamine, thyroid hormones, and melanin.
- Glycine is a precursor of heme, porphyrin, and creatine.
- Arginine is a precursor of nitric oxide, spermidine, and spermine.
- Methionine is a precursor of S-adenosylmethionine, spermidine, and spermine.
Neurotransmitters
- Neurotransmitters are derived from amino acids: Histamine from Histidine, Serotonin from Tryptophan, Dopamine from Tyrosine, and Acetylcholine from Serine.
Classification of Amino Acids Based on Metabolism
- Glucogenic amino acids: 13 amino acids that degrade to TCA intermediates.
- Both glucogenic and ketogenic amino acids: 5 amino acids that degrade to TCA intermediates and produce ketone bodies.
- Ketogenic amino acids: 2 amino acids that produce ketone bodies: Leucine and Lysine (although most references classify Leucine as the only strictly ketogenic amino acid).
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