Amino acid metabolism: practice question

The best answer is A, Phenylalanine hydroxylase. Phenylalanine hydroxylase converts phenylalanine to tyrosine using tetrahydrobiopterin.

Tyrosinase deficiency causes albinism by blocking melanin synthesis.

Homogentisate oxidase deficiency causes alkaptonuria, with dark urine and arthropathy.

Fumarylacetoacetate hydrolase deficiency causes hereditary tyrosinaemia type I.

It tests Amino acid metabolism in Biochemistry. Its deficiency raises phenylalanine, causing intellectual disability, a musty odour and fair skin if untreated. Newborn screening and a low-phenylalanine diet prevent damage.

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.