Overview and purpose of urea cycle — Flashcards

Flashcard 1: Hyperammonemia results in excess NH3, which depletes _____, leading to inhibition of the TCA cycle

Answer: α-ketoglutarate

Flashcard 2: Most excess nitrogen generated by catabolism of amino acids is excreted as _____, which is made in the liver

Answer: urea

Flashcard 3: Ornithine transcarbamylase (OTC) deficiency presents with _____ serum glutamine

Answer: increased

Flashcard 4: Most disorders of the urea cycle require _____ as an essential amino acid, particularly during episodes of hyperammonemia

Answer: arginine

Flashcard 5: What other enzyme deficiency presents identically to carbamoyl phosphate synthetase I deficiency? _____

Answer: N-acetylglutamate synthase deficiency

Flashcard 6: What is the rate-limiting enzyme of the urea cycle? _____

Answer: Carbamoyl phosphate synthetase I

Flashcard 7: What class of enzymes is used in the transfer of amino groups during nitrogen metabolism?

Answer: Aminotransferases (Transaminases)

Flashcard 8: Disorders of the urea cycle interfere with the body's ability to eliminate _____

Answer: ammonia (NH3)

Flashcard 9: Where does the urea cycle occur?

Answer: steps in both the cytoplasm and mitochondria

Flashcard 10: What is the rate-limiting enzyme of the Urea Cycle?

Answer: Carbamoyl phosphate synthetase I (CPS I)

Extra: CPS I is the rate-limiting enzyme of the urea cycle and is activated by N-acetylglutamate (NAG). It is located in the mitochondria.