Step 1

Biochemistry 15

A 15-year-old girl presents to a psychiatrist for an initial intake appointment. She reports decreased mood, decreased appetite, anhedonia, and difficulty concentrating for the past 3 months. She does not use any illicit substances, and her screening laboratory tests are unremarkable. A presumptive diagnosis is made.

Which of the following amino acids is necessary to synthesize the neurotransmitter whose synaptic concentration is increased by the first-line treatment for this patient’s condition?

  • A) Histidine
  • B) Isoleucine
  • C) Threonine
  • D) Tryptophan
  • E) Tyrosine


Tyler Natof


Dr. Ted O'Connell