Question

Phenylketonuria is a genetic disorder due to a defect in metabolism of which of the following?

• A. Polysaccharides
• B. Fatty acids
• C. Vitamins
• D. Amino acids
• E. Hormones

Answer 1

Answer: (D)

Amino acids

The genetic metabolic disorders in which the body is unable to metabolize food into energy are called inborn errors of metabolism. They are usually caused by defective metabolic proteins (enzymes). Phenylketonuria is an inborn error of metabolism because the newborn is unable to properly break down the amino acid called phenylalanine. It is caused by absence of an enzyme called phenylalanine hydroxylase, which breaks down phenylalanine into tyrosine.