Ornithine-urea cycle, Biology

Assignment Help:

Ornithine-urea cycle

The synthesis of urea (H2N.CO.NH2) from one molecule of CO2 and two of NH, occurs in the liver of ureotelic vertebrates by a metabolic pathway known as the ornithine-urea cycle, discovered by Kreb and Hensleit in 1932. This is a cyclic pathway that involves five enzyme-catalised reactions.

647_Ornithine-urea cycle.png

                                                                           Figure:  Ornithine-urea cycle

You can see in Figure that this cycle has five steps :

  1. Ammonia, CO2 and ATP are converted into carbamoylphosphate by the enzyme, carbamoylphosphate synthetase.
  2. Ornithine carbamoyl-transferase then makes citrulline from carbamoylphosphate and ornithine.
  3. Citrulline is then used in the presence of ATP and aspartic acid for the synthesis of argininosuccinic acid by the enzyme argininosuccinate synthetase.
  4. Argininosuccinic acid then gives rise to arginine and fumararic acid in the presence of argininosuccinate lyase. In the formation of afginine from citrulline, the amino group of as paratic acid is used with the release of the carbon skeleton of the aspertic acid in the form of fumararic acid.
  5. Finally, the cycle is completed by splitting arginine into urea and ornithine in the presence of the enzyme arginase.

Related Discussions:- Ornithine-urea cycle

Define some advantages of breast milk for infants, Define some Advantages o...

Define some Advantages of breast milk for Infants? 1) Breast milk is a simple and natural method of feeding. It is hygienic, inexpensive and available at all times at the righ

Metabolism of pollen tubes, Metabolism of Pollen Tubes Pollen grains ...

Metabolism of Pollen Tubes Pollen grains contain auxins, and gibberellins which are known to be involved in post- pollination enlargement of the ovary and the development of

Management of diabetes, By now you know that diabetes cannot be cured but c...

By now you know that diabetes cannot be cured but can be treated so that an individual leads a normal life. Patients who maintain their blood glucose levels within the normal range

Cryobiology, Cryobiology : This is the study of life at low temperature. Cr...

Cryobiology : This is the study of life at low temperature. Cryobiology is that branch of biology which studies the effects of low temperatures on living things. Cryobiology scienc

Define glycogenolysis, Define Glycogenolysis Glycogenolysis : degrad...

Define Glycogenolysis Glycogenolysis : degradation of glycogen.

Explain first stage of the embryonic development, Q. What is the cell divis...

Q. What is the cell division during the first stage of the embryonic development called? How is this stage characterized? The cell division in the first stage of the embryonic

How aggregation occur in sickle-cell anemia, How does aggregation occur in ...

How does aggregation occur in sickle-cell anemia? Place the steps in the correct order from no aggregation to sickle red blood cell. Note that deoxyhemoglobin is generally in the T

Describe the functionality of pectin, Functionality Pectins are mainly ...

Functionality Pectins are mainly used as gelling agents, but can also act as a  thickener, water binder and stabilizer. Low methoxyl pectins ( 2+ ions. Highly acetylated pecti

Succession, Similarities between autotrophic succession and heterotrophic s...

Similarities between autotrophic succession and heterotrophic succession

Define why the virginia opossum is considered a generalist, Define why the ...

Define why the Virginia opossum is considered a generalist and the koala is considered a specialist. The opossum feeds on almost anything, whereas the koala feeds only on the l

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd