Which amino acid binds NH4+ covalently and makes it non-toxic for transpoation ?
**Core Concept**
The detoxification of ammonium ions (NH4+) is crucial in the body to prevent its toxic effects. This process involves the conversion of ammonia into a less toxic form, which can be safely excreted. The amino acid responsible for this process is glutamine, which plays a key role in the transport and removal of ammonia from the brain and other tissues.
**Why the Correct Answer is Right**
Glutamine is the primary amino acid involved in the detoxification of ammonia in the body. It binds to NH4+ covalently through a process called conjugation, forming glutamine (NH2-C(=O)-NH-CH2-CH2-NH2). This reaction is catalyzed by the enzyme glutamine synthetase, which is present in the brain, liver, and kidneys. The resulting glutamine molecule is then transported out of the cells and excreted by the kidneys, making ammonia non-toxic for transportation.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because there is no known amino acid that binds NH4+ covalently and makes it non-toxic for transportation other than glutamine.
**Option B:** This option is incorrect because asparagine, although similar to glutamine, is not the primary amino acid involved in the detoxification of ammonia.
**Option C:** This option is incorrect because glycine, although a non-essential amino acid, is not directly involved in the detoxification of ammonia.
**Option D:** This option is incorrect because alanine, although involved in various metabolic processes, is not the primary amino acid responsible for binding NH4+ and making it non-toxic for transportation.
**Clinical Pearl / High-Yield Fact**
Glutamine is an important amino acid in the body, not only for its role in ammonia detoxification but also for its role in gut health and immune function. Deficiencies in glutamine can lead to various clinical conditions, including muscle wasting, impaired gut function, and increased susceptibility to infections.
**Correct Answer:** C. Glutamine.