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Urea Formation
Concepts tested here
- Ornithine cycle
All Questions
2005 AIPMT 1 question
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In ornithine cycle which of the following wastes are removed from the blood -The ornithine cycle (Krebs-Henseleit cycle, urea cycle) takes place in the liver cells.
In this cycle ammonia, produced by the deamination of amino acids, combines with carbon dioxide to form urea.
$2NH_3 + CO_2 \rightarrow CO(NH_2)_2 + H_2O$
Ornithine combines with $NH_3$ and $CO_2$ (as carbamoyl phosphate) to form citrulline, which takes up another $NH_2$ group to form arginine; arginine is split by arginase into urea and ornithine.
So the toxic ammonia and the waste $CO_2$ are removed from the blood, and the less toxic urea is formed and released into the blood to be excreted by the kidneys.
So the wastes removed are $CO_2$ and ammonia.