Proteins are made of carbon, hydrogen and oxygen like any other macronutrient. However, what sets proteins apart from the rest is their nitrogen group. Amino acids give each protein its identity and alerts the body to how the protein should be used. Protein digestion and metabolism is a complex operation that your body performs ingeniously.
Amino Acids
The nitrogen containing portion of a protein is called an amino acid. Your body needs 20 different amino acids, about half of which your body can make. The rest need to be part of your diet. Dietary amino acids can be obtained through lean meats, eggs, fish, legumes and dairy.
Protein Metabolism
In order for a protein to be metabolized, the nitrogen must first be removed. The first part of this process is oxidative deamination. This occurs inside of the liver and removes the nitrogen from the amino acid. The second step is transamination, in which the amino acid is transported outside of the liver to preform its job.
Products of Metabolism
The end product of protein metabolism is nitrogen. Your body considers nitrogen as waste. Some nitrogen is transformed into ammonia and excreted, but most is turned into urea and taken care of by the kidneys. Nitrogen can cause the pH of your blood to rise, which puts stress on the heart and cardiovascular system.
Urea Cycle
After nitrogen is removed from the protein, it is sent into the blood by the liver and travels to the kidneys for excretion via the urine. The urea cycle is the process by which the nitrogen is sent out of the body as waste. Nitrogen disposal is a complex process that requires a great deal of energy to perform compared to other biological processes.
Function of Amino Acid
For all of the work your body does to get rid of the byproducts of protein metabolism, it must get something important out of it. Protein is responsible for many bodily functions. It helps to build skeletal and smooth muscle, antibodies, enzymes and hormones. It also maintains the fluid and electrolyte balance of cells and the pH of your blood.
References
- "Nutrition: Concepts and Controversies"; Sizer, Francis, Whitney, Eleanor; 2004
- "Exercise Physiology"; Brooks, George A., Fahey, Thomas D., Baldwin, Kenneth M.; 2005
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