Ureotelism: Process, Urea Cycle & Significance

Ureotelism is the process in which urea is eliminated from the body. When an organism's body lets go of toxic substances from the kidneys, lungs, and skin, the process is known as excretion. For example, the lungs excrete carbon dioxide whereas the skin passes salt and water in the form of sweat from our body, and the kidneys being the main excretory organs, eliminate excess water from the body. Those animals which excrete the waste in which the central part is urea is referred to as Ureotelic Animals. 

Key Terms: Ureotelism, Urea, Excretion, Urea Cycle, Elimination, Ammonia, Ornithine Urea Cycle, Mammals

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Process of Ureotelism

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The process by which urea is excreted from our body is known as ureotelism. The categories which exhibit ureotelism are mostly mammals, marine fish, and amphibians. 

• Ammonia is produced as a result of the metabolism of the body and the excess ammonia is converted into urea by the liver. The process in which ammonia is taken out from the body is known as ammonotelism. 
• The urea produced is then discharged into the bloodstream and the urea acting as a waste in the blood is filtered out by the body this process is known as excretion, excretion is very important is it maintains the acid-base balance and is also responsible for controlling osmotic pressure in our body. 

Read More: Excretion in Human Beings

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Composition of Urea 

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Urea is a colorless and crystalline compound that is obtained as a result of the nitrogenous product during the digestion of protein by our body. When ammonia is present in excess as a result of the breakdown of excess amino acid in our body, it becomes harmful for the body so to protect the body, the ammonia is further broken down by our body into urea by the liver. This cycle repeats itself and is termed the urea cycle. 

Urea is basically composed of nitrogen, oxygen, and carbon and is usually found in blood, sweat, urine, etc in our body.

Urea Cycle

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Excess Urea Accumulation in The Body

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Ureotelism is very important in the body as urea is very dangerous to many organs in the body which can rupture the organs both directly as well as indirectly. 

• High urea levels can cause the increased synthesis of bacteria in the body and can also result in the breakdown of the intercellular connection due to the inflammation in the walls of the intestine. 
• Furthermore, a high level of urea in the blood can cause cell death and insulin sensitivity which may result in a person being pre-diabetic and can also cause chronic kidney disease. 
• A high level of urea can also cause renal failure and another cardiovascular disease. 

These were the direct impact of high accumulation of urea, there are many indirect impacts like irreversible carbamylation, and cyanate exposure and all of these can lead to the death of the patient. These adverse effects in the body due to the high accumulation of urea make the process of ureotelism very important for the body.

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Ornithine Urea Cycle

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Hensleit and Kerb discovered the cycle in 1932 known as the Ornithine-Urea Cycle where the three ATP molecules activate when ammonia is dissolved. Five chemical processes are responsible for the completion of the cycle by the enzymes. 

In the first process, Carbamoyl phosphate is made with the help of ammonia, carbon dioxide, and ATP. Now with the help of Carbamoyl phosphate and Ornithine, citrulline is made which is again treated with aspartic acid in the presence of ATP to make argininosuccinic acid. At last Ornithine and urea are formed as a result of the breakdown of arginine. These five processes with the help of complex enzymes are responsible for the completion of the Ornithine urea cycle. It is much different from the normal urea cycle as the urea cycle doesn't involve such a complex compound to get carried out.

Read More: Test for Presence of Urea in Urine

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Elimination and Its Biological Significance

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The most common component of excretion is urine which has various components including, urea, ammonia, water, and other chemicals. Biologically all organisms must consume energy for their daily processes, take a small part of the energy for their living and dispose of the rest through the process of elimination. There is a various metabolic and non-metabolic process that goes on in the body and requires energy to undergo the process. 

But the amount of energy present in the body is more than sufficient to counter all the processes hence a good part of energy remains stored and the rest is excreted out. Now conversion of ammonia to urea needs a certain amount of energy and the process of ureotelism also needs the energy to be carried out this way, the energy is excreted in the form of various conversions and processes.

Read More: Ammonium Chloride

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Things to Remember

• The excretion of urea is known as ureotelism.
• The liver converts ammonia to urea which is then excreted by the kidneys if they are in excess. 
• Ammonia is more hazardous as a result of which urea is eliminated as two nitrogen atoms are excreted with less water at a time.
• Ureotelism is very important in the body as urea is very dangerous to many organs in the body which can rupture the organs both directly as well as indirectly.