Q. 18.67 - An Introduction to General, Organic, and Biological Chemistry

Question

Why does the body convert ${\mathrm{NH}}^{4+}$ to urea?

Step-by-Step Solution

Answer

If allowed to build, the ammonium $\left({\mathrm{NH}}^{4+}\right)$ ion, which is the end result of amino acid breakdown, is hazardous. Therefore, a series of reactions, called the urea cycle , detoxifies ammonium $\left({\mathrm{NH}}^{4+}\right)$ ion by forming urea , which is excreted in the urine. 

Step 1: Given information

We need to find out why does our body convert ${\mathrm{NH}}^{4+}$ to urea.

Step 2: Explanation

Ammonia is a hazardous byproduct of nitrogen metabolism that should be eliminated. In the mitochondria of liver cells, the urea cycle turns excess ammonia to urea. The urea is formed, then injected into the bloodstream, filtered by the kidneys, and expelled in the urine. 

$$\begin{gathered} 2{\mathrm{NH}}^{4+} + {\mathrm{CO}}_2\to {\mathrm{NH}}_2-\mathrm{CO}-{\mathrm{NH}}_2 + 2{\mathrm{H}}^{+} + {\mathrm{H}}_2\mathrm{O} \\ \mathrm{Ammonium} \mathrm{Urea} \\ \mathrm{ion} \end{gathered}$$