Amino Acid & Protein Metabolism · NEET PG Preparation Biochemistry
A 45-year-old man comes to the physician because of progressive fatigue, joint pain, and bluish-black discoloration of his sclerae and ear cartilage.…
Practice question from Amino Acid & Protein Metabolism (NEET PG Preparation Biochemistry), with the correct answer and a step-by-step solution.
medium · MCQ · Q-A64A71
A 45-year-old man comes to the physician because of progressive fatigue, joint pain, and bluish-black discoloration of his sclerae and ear cartilage. His urine turns dark upon standing when exposed to air. This patient's condition is most likely caused by a deficiency of which of the following enzymes?
- A.Tyrosinase
- B.Homogentisate 1,2-dioxygenaseCorrect answer
- C.Fumarylacetoacetate hydrolase
- D.Alpha-keto acid dehydrogenase
Solution
Alkaptonuria is an autosomal recessive disorder caused by a deficiency of homogentisate 1,2-dioxygenase in the degradation pathway of tyrosine and phenylalanine. This leads to an accumulation of homogentisic acid, which binds to collagen in connective tissues (ochronosis) and oxidizes to a dark pigment when exposed to air in urine.
More from Amino Acid & Protein Metabolism
- A 7-day-old neonate presents with poor feeding, vomiting, and a maple syrup-like odor to the urine. Laboratory evaluation reveals severe me…
- During the urea cycle, which of the following molecules acts as an essential allosteric activator of carbamoyl phosphate synthetase I (CPS…
- A 6-year-old boy is brought to the clinic for evaluation of tall stature, long slender fingers (arachnodactyly), downward lens dislocation…
- Which of the following amino acids is strictly ketogenic and cannot serve as a substrate for net hepatic gluconeogenesis?
Practise more Biochemistry
Sign up free for adaptive practice on this chapter, with instant feedback and hints on every question.
Start practising freeFree to start · No credit card needed