Chapter 26, Problem 26.69EP

Interpretation Introduction

Interpretation: To determine the amount of energy, in terms of ATP consumption expended in the formation of a molecule of urea from ammonium ion and oxaloacetate.

Concept introduction: Urea cycle is a cyclic biochemical pathway that involves the production of urea using ammonium ions and aspartate molecules as nitrogen sources. It converts toxic ammonium ion to urea which is then excreted from the body in urine.

Urea cycle 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.