Question

Name the process in mammal during which urea is formed

Answer 1

Answer:

his series of reactions is called the ornithine cycle. The urea and water are released from the liver cells to the bloodstream and transported to the kidneys where the blood is filtered and the urea is passed out of the body in the urine.

Explanation:

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Answer 2

Answer:

The process by which urea is produced in mammals is called Urea cycle or Ornithine cycle. It occurs predominantly in hepatocytes present in our liver cells and to a smaller extent it also takes place in our kidneys.

Explanation:

It occurs because it gives us a way to transform a toxic by-product of amino acid metabolism called ammonium into less toxic form called Urea, which can then be mobilized and transported to the kidneys where they excrete the urea via urine.

Brief account of 5 steps of Urea cycle-

1st place of occurrence- Mitochondria of liver cell- 2 of the first steps occurs here.

1. Excess of ammonia that comes from amino acid metabolism combines with carbon dioxide to form a high energy molecule called carbamoyl phosphate using 2 molecules of ATP

2. Citrulline is formed by combination of carbamoyl phosphate already present in the matrix of mitochondria and ornithine that goes into mitochondria from the cytoplasm.

Citrulline then moves into the cytoplasm of the cells

2nd place of occurrence- Cytoplasm of hepatocytes present in liver cells- last 3 steps occur here.

3. In the cytoplasm, citrulline combines with aspartate to form- Arginosuccinate.

4. Arginosuccinate is then broken down into Arginine and Fumarate.

• Fumarate is formed by carbon skeleton of aspartate. (Fumarate is later used in gluconeogenesis that also occurs in liver cells)

• Arginine is formed by the amino group present in aspartate (this amino group is 2nd amino that group can be seen later in urea).

5. Arginine is then hydrolyzed by a water molecule which leads to formation of urea and ornithine, urea is then removed and ornithine is the amino acid that recycled back into the matrix of mitochondria.