The role of amino acids as the first nutrient element in the body, its role in food nutrition is obvious, but it can not be directly used in the human body, but by being turned into small amino acid molecules after being used. That is, it is not directly absorbed by the human body in the gastrointestinal tract of the human body, but it is absorbed in the small intestine through the action of various digestive enzymes in the gastrointestinal tract, which decomposes the polymer protein into low-molecular-weight polypeptides or amino acids. Enter the liver along the portal vein. Some amino acids decompose or synthesize proteins in the liver; another part of amino acids continues to distribute with the blood to various tissues and organs, allowing them to select and synthesize various specific tissue proteins. Under normal circumstances, amino acids enter the bloodstream at almost the same rate as their output, so normal human blood has a fairly constant amino acid content. If amino nitrogen is used, the content per milliliter of plasma is 4 to 6 milligrams, and the content per milliliter of blood corpuscle is 6.5 to 9.6 milligrams. After eating the protein, a large number of amino acids were absorbed and the blood amino acid levels temporarily increased. After 6 to 7 hours, the content returned to normal. It shows that the amino acid metabolism in the body is in a dynamic equilibrium, with blood amino acid as its equilibrium hub, and the liver is an important regulator of blood amino acids. Therefore, food proteins are absorbed by the body after being digested and broken down into amino acids, and antibodies use these amino acids to synthesize their own proteins. The human body's need for protein is actually a need for amino acids.
When the quality and amount of protein in the daily diet are appropriate, the amount of nitrogen ingested by the feces, urine and skin is equal to the amount of nitrogen, which is called the total balance of nitrogen. It is actually a balance between the constant synthesis and decomposition between proteins and amino acids. Normal daily intake of protein should be kept within a certain range, suddenly increase or decrease the amount of intake, the body can still regulate the amount of protein metabolism to maintain nitrogen balance. Ingestion of excessive protein, beyond the body's ability to adjust, the balance mechanism will be destroyed. If you do not eat protein at all, the body tissue protein will still be decomposed and the negative nitrogen balance will continue to appear. If you do not take timely measures to correct it, you will eventually lead to the death of the antibody.
Turn into fat
The a-keto acid produced by the amino acid catabolism is metabolized along with different characteristics, through metabolic pathways of sugar or lipid. A-keto acid can be re-synthesized to a new amino acid, or converted into sugar or fat, or into the tricarboxylic acid cycle to oxidatively decompose to CO2 and H2O, and release energy.
Generate a carbon unit
Some amino acid catabolism produces groups containing one carbon atom, including methyl, methylene, methoyl, methynyl, cresyl, and iminomethyl groups.
One carbon unit has the following two characteristics: 1. Cannot exist in free form in vivo; 2. Must use tetrahydrofolate as carrier. The amino acids that produce one carbon unit are: serine, tryptophan, histidine, and glycine. In addition, methionine (methionine) can provide "active methyl" (1-carbon unit) via S-adenosylmethionine (SAM), so methionine can also generate one-carbon unit. The main physiological function of the one-carbon unit is as a raw material for the synthesis of purines and pyrimidines, and is a link between amino acids and nucleotides.