Final answer:
Ammonia is primarily transported through the blood as glutamine. It is then converted into urea in the liver and excreted through the kidneys. This transport and conversion process is vital for detoxifying ammonia and maintaining the body's acid-base balance.
Step-by-step explanation:
The molecule used to transport ammonia through the blood is primarily glutamine. Ammonia (NH3), a toxic byproduct of protein metabolism, is formed when amino acids are deaminated. To safely transport ammonia from various tissues to the liver where it can be converted into less toxic compounds, it attaches to ammonia carriers such as amino acids. Glutamine carries it from the brain and peripheral tissues, while alanine transports it from the muscles.
Glutamine not only serves as the primary carrier for ammonia but is also used in the kidneys where it can be deaminated to release NH3. The ammonia is then converted into urea via the urea cycle, a process which takes place in the liver. The urea formed is then excreted by the kidneys. This conversion to urea helps maintain the acid-base balance and is critical for the conservation of vital cations like Na+ and K+ ions. It also contributes to the osmoregulatory function of the kidneys by allowing the body to reclaim water and sodium from urine. The renal production of ammonia is an essential physiological process that is tightly regulated.
Ammonia transported through these mechanisms is eventually excreted by humans in the form of urea, a process known as ureotelism, which is critical for eliminating the toxic effects of ammonia in the body.