Metabolic Flashcards
What are the 4 classes of macromolecules in the cell?
Proteins, lipids, carbohydrates, and nucleotides
Summarize the catabolism and anabolism of the major classes of macromolecules of the cell.
Summarize the catabolism of the essential amino acids.
What is the defect responsible for classic Phenylketonuria?
A mutation in phenylalanine hydroxylase (PAH), preventing conversion of phenylalanine to tyrosine.
What are the symptoms of PKU?
Vomiting, irritability, eczematoid rash, mousy odor. Diagnosis in neonatal period is essential.
What is the treatment for PKU?
Limitation of dietery Phenylalanine (before 14 days of life). Some basal Phenylalanine is necesssary for normal growth and development, and Tyrosine is an essential AA in these patients.
Tetrahydrobiopterin is an essential cofactor for the hydroxylation of which three amino acids?
Phenylalanine, Tryptophan, and Tyrosine.
What is the treatment for biopterin synthesis defects?
Dietary limitation of phenylalanine, and supplementation of 5-hydroxytrptophan and dopa (biogenic amine precursors to compensate for inability to metabolize tryptophan and tyrosine, respectively.)
What defect may be present in a patient with hyperphenylalaninemia whose neurological symptoms worsen despite phenylalanine restriction?
Defects in the synthesis or recycling of biopterin.
Which AA is often highly elevated in newborns, particularly premature newborns?
Tyrosine. (This leads to many false positive PKU screens as it stoichiometrically impairs phenylalanine conversion to tyrosine).
Hepatomegaly with adenomas/hepatoblastomas, liver failure, and renal tubular acidosis (similar to fanconi syndrome) may be indicative of which metabolic disorder?
Hereditary tyrosinemia Type I, a deficiency of fumarylacetoacetase (the final step in tyrosine metabolism) leading to accumulation of succinylacetone.
A patient with corneal ulcers or keratitis and red papular or keratotic lesions of the palms and soles may have which metabolic disorder?
Tyrosinemia Type II, a deficiency of tyrosine aminotransferase (the first step in tyrosine metabolism).
A patient presenting with ataxia, repeated episodes of lethargy, anion gap acidosis, but normal IQ may have what metabolic disorder?
A mild variant of maple syrup urine disease (impaired catabolism of the branched chain ketoacids that are formed by the catabolism of the branched chain amino acids).
What are the three branched chain amino acids?
Leucine, isoleucine, valine
What is the treatment for Tyrosinemia Type I?
Nitisinone, which blocks Tyrosine catabolism prior to formation of succinylacetone. Since this results in build up of Tyrosine, patients must also be on a diet low in both Tyrosine and phenylalanine.
