Urea Cycle Lab Report

Urea cycle

Introduction

The task of urea cycle is to avoid the amassing of toxic NH4+. It incorporates nitrogen not used for biosynthetic purposes into urea, which serve as the waste nitrogen produce in mammals. Urea is the major disposal form of amino groups derived from amino acids, and account for about 90% of the nitrogen-containing gears of urine. Also urea cycle is accountable for de novo synthesis of arginine. The complete Urea Cycle is by far only in liver. However, some enzymes of the pathway are in other cells and tissues where they produce arginine & ornithine e.g., Argininosuccinate Synthase, which catalyzes synthesis of the precursor to arginine, is in large amount tissues [Jones et.al 2000].

Reactions of the cycle

The urea cycle consists of 5 reactions. The first reaction occurs in the matrix of the mitochondria. The following reactions occur in the cytosol. This is a pathway

This step takes place in liver and kidney of mammals. The enzyme cleaves arginosuccinate to form arginine and fumarate. The arginine formed by this reaction serve as the immediate forerunner of urea. Fumarate created in the urea cycle is hydrated to malate, providing a link with several metabolic pathways. For example, the malate can be transported into the mitochondria via the malate shuttle and re-enter the tricarboxylic acid cycle. Then again, cytosolic malate can be oxidized to oxaloacetate, which can be converted to aspartate or glucose [Jones et.al 2000]. Step 5: Hydrolysis of arginine to form ornithine and urea

Enzyme Arginase is required in this step. The arginine is hydrolyzed to generate the urea and to change the ornithine. It occurs in liver cells cytosol. The ornithine re-enters the mitochondrial matrix. Urea is excreted. Hence, whereas other tissues, such as the kidney, can synthesize arginine by these reactions, only the liver can cleave arginine and, thereby, synthesize urea [Jones et.al 2000]. Fate of