Chapter 26.9, Problem 1QQ

Interpretation Introduction

Interpretation: To identify the process by which fumarate produced during urea cycle operation is processed further.

Concept introduction: A urea cycle is a cyclic biochemical pathway that involves the production of urea using ammonium ions and aspartate molecules as nitrogen sources. The desired product of the urea cycle is urea. It constitutes 4 steps. In step 1 carbamoyl phosphate transfers its carbamoyl group to ornithine to produce citrulline. Citrulline then condenses with aspartate in the second step to form argininosuccinate which then cleaves in the third step to form arginine and fumarate. In the final step, arginine reacts with water to produce urea.