Protein constitutes the material basis of life without which there is no life. The function of the protein is to make up and repair the body’s cells and tissues, promote the growth and development, participate in the body’s metabolism, form antibodies, enhance the immunity and supply the heat energy. Therefore, it is a matter that is closely linked with life and all kinds of life activities. Every cell in the body and all important components have protein involved. Protein accounts for 16.3% of the body weight, that is, a 60kg weight of the body about 9.8kg of protein in the body. Many kinds of proteins in the human body, nature, function, but are composed of more than 20 kinds of amino acids by different combinations, and continue to be metabolized and updated in the body.
In addition to the energy supplied, the protein in food is mainly used as raw material for body growth, renewal and repair. The process of muscle growth is actually myofibrillar protein supplement process. However, protein and other nutrients are different, its molecular weight, composition is complex, without body digestion, decomposition, difficult to absorb, but also cause systemic reactions.
Regardless of the type of protein ingested by the body, it is first chewed into smaller units through the tearing of the teeth, although there are many enzymes in the mouth but little digestion of the protein.
Stomach is the first step in protein digestion. Protein digestion is basically the protein hydrolysis process. According to the degree of hydrolysis can be divided into complete hydrolysis and incomplete hydrolysis.
- 1 Completely hydrolyzed: Hydrolysis products obtained by thorough hydrolysis is a mixture of various amino acids.
- 2 Partial hydrolysis: Hydrolysis products obtained by incomplete hydrolysis are various sizes of peptides and a single amino acid. Proteins in the stomach by the role of enzymes, broken down into peptides; when the peptide into the intestinal mucosal epithelial cells, immediately after the hydrolysis of the peptide within the cell into the most basic components of proteins – amino acids. Amino acids are mainly absorbed in the small intestine. It also wants to pass through the delivery vehicles, accompanied by sodium, in order to pass through the intestinal mucosa at this level into the blood.
After the amino acids are absorbed in the small intestine, they enter the liver along the hepatic portal vein. A portion of amino acids in the liver to decompose or synthesize protein; the other part of the amino acids continue to distribute to various tissues and organs with the blood, let them choose to synthesize a variety of specific tissue proteins. Under normal circumstances, amino acids into the blood almost equal to its output rate, so the normal blood amino acid content is fairly constant. Such as amino acids, per 100 ml of plasma content of 4 to 6 mg per hundred ml of blood cells in the content of 6.5 to 9.6 mg. After eating protein, a large number of amino acids are absorbed, the blood levels of amino acids temporarily increased after 6 to 7 hours, the content returned to normal. This shows that the metabolism of amino acids in the body is in a state of equilibrium, with the blood amino acids as the balance hub, and the liver is an important regulator of blood amino acids. Therefore, the food protein is digested and broken down into amino acids and then absorbed by the human body. Antibodies use these amino acids to synthesize their own proteins. The body’s need for protein is actually a need for amino acids.
Amino acids in the liver will be catabolized, that is, deamination, amino acid deamination process, the process of nitrogen compounds generated in the liver into urea, non-nitrogen part of the process into carbohydrates or fat, Midway also produces water and carbon dioxide.
Under deamination, the amino acids eventually form useful sugars or fats and useless urea and carbon dioxide. Sugar and fat are absorbed or stored, and carbon dioxide is eventually exhaled into the vein by the lungs. Most of the urea is eliminated by the urine and a small portion is eliminated by sweat.
Summary: After protein is finally broken down into amino acids, some form sugar or fat, some enter the bloodstream to reach the body’s own body to synthesize human tissue proteins, and some of the components become urea and carbon dioxide which are excreted.