Chapter 15, Problem 15.110EP

Interpretation Introduction

Interpretation: To determine the two molecules involved in the connecting link from the citric acid cycle to the urea cycle.

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.

The citric acid cycle is a series of eight chemical reactions used to release energy by all aerobic organisms. The acetyl part of $\text{acetyl CoA}$ is oxidized with the release of ATP and carbon dioxide.