University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

171

Pages:

6
Author:

Sheha A.

Urea Cycle / Ornithine Cycle The urea cycle is a cycle of biochemical reactions occurring in many animals that produces urea [(NH₂)₂CO] from NH₃. Site: Liver Kidney: filters out the urea and then excreted in the urine. Reactions of Urea Cycle Synthesis of carbamoyl phosphate and entry into the urea cycle Formation of citrulline Formation of argininosuccinate Cleavage of argininosuccinate Cleavage of arginine Visual Description: The image consists of two parts, both related to the urea cycle, a biochemical process that occurs in many animals to eliminate excess nitrogen. Part 1: Provides a brief overview of the urea cycle, explaining its purpose and the organs involved. Highlights the liver as the primary site of urea production and the kidneys as the organs responsible for its excretion. Synthesis of carbamoyl phosphate Ammonia enters the cycle after condensation with bicarbonate to form carbamoyl phosphate. This reaction is catalyzed by carbamoyl phosphate synthetase I and uses two ATP molecules. Formation of citrulline Carbamoyl phosphate donates its carbamoyl group to ornithine and forms citrulline with the release of Pi. The reaction is catalyzed by ornithine transcarbamoylase. 3. Formation of argininosuccinate Second amino acid that enters into the cycle from aspartate by condensation reaction b/w the amino group of aspartate and carboxyl group of citrulline, forming argininosuccinate. This reaction is catalyzed by argininosuccinate synthetase. This reaction requires 1 ATP molecule. 5. Cleavage of Arginine In the last reaction of the urea cycle, arginase cleaves arginine to yield urea and ornithine. Ornithine is transported into the mitochondria and initiates another round of the urea cycle. Urea Cycle The image depicts a diagram of the urea cycle, a biochemical process that occurs in the liver of mammals to convert toxic ammonia into less toxic urea. The cycle involves several enzymes and intermediates: Carbamoyl phosphate synthetase I catalyzes the synthesis of carbamoyl phosphate from ammonia, carbon dioxide, and ATP. Ornithine transcarbamoylase catalyzes the transfer of the carbamoyl group from carbamoyl phosphate to ornithine, forming citrulline. Argininosuccinate synthetase catalyzes the condensation of citrulline and aspartate to form argininosuccinate. Argininosuccinate lyase cleaves argininosuccinate into arginine and fumarate. Arginase cleaves arginine into urea and ornithine. The cycle is shown as a circular pathway, emphasizing its cyclical nature. The enzymes involved in each step are labeled, and the flow of metabolites is indicated by arrows.