I. The basic substances that make up the human body, the material basis of life
1. One of the most basic substances that make up the human body
The most basic substances that make up the human body, there are proteins, lipids, carbohydrates, inorganic salts, vitamins, water, and dietary fiber.
Amino acids, which are the basic units that make up the protein molecule, are undoubtedly one of the most basic substances that make up the human body.
There are more than 20 kinds of amino acids that constitute the human body, they are: tryptophan, methionine, threonine, valine, lysine, histidine, leucine, isoleucine, alanine, phenylalanine, cystine, cysteine, arginine, glycine, serine, tyrosine, 3.5.diiodotyrosine, glutamic acid, aspartic acid, proline, hydroxyproline, arginine, citrulline, ou amino acid, citrulline, ouabain, etc. These amino acids are found in nature and can be synthesized in plants, while the human body cannot synthesize all of them. Eight of these amino acids cannot be synthesized by the human body and must be supplied by food, and are called "essential amino acids". These 8 essential amino acids are: tryptophan, threonine, methionine, valine, lysine, leucine, isoleucine and phenylalanine. The others are "non-essential amino acids". Histidine can be synthesized in the body, but the rate of synthesis is not sufficient to meet the body's needs, and some people also classify it as an "essential amino acid". Cystine, tyrosine, arginine, serine and glycine may cause physiological dysfunction in the long-term lack of, and listed as "semi-essential amino acids", because they can be synthesized in the body, but its synthesis of raw materials are essential amino acids, and cystine can replace 80% to 90% of methionine, tyrosine can replace 70% to 75% of the phenylalanine, play a role in the essential amino acids. Phenylalanine, play the role of essential amino acids, the above amino acids are divided into "essential amino acids", "semi-essential amino acids" and "non-essential amino acids" 3 categories, according to its nutritional function. Functions; such as its metabolic pathway in the body can be divided into "ketogenic amino acids" and "sugar amino acids"; according to its chemical properties can be divided into neutral amino acids, acidic amino acids and alkaline amino acids, most of the amino acids belong to the neutral.
2. The material basis of life metabolism
The generation, existence and demise of life, none of which is related to protein, as Engels said: "Protein is the material basis of life, life is a form of protein existence." If the lack of protein in the human body, the light body quality decline, development retardation, weakened resistance, anemia and weakness, the heavy formation of edema, and even life-threatening. Once the loss of protein, life will no longer exist, so some people call protein as "the carrier of life". It can be said that it is the first element of life.
The basic unit of protein is amino acid. If the human body lacks any one of the essential amino acids, it can lead to abnormal physiological functions, affecting the normal metabolism of antibodies, and finally lead to disease. Similarly, if the human body is deficient in certain non-essential amino acids, antibody metabolism disorders can arise. Arginine and citrulline are important for the formation of urea; insufficient intake of cystine can cause a decrease in insulin and an increase in blood glucose. Another example is that the need for cystine and arginine increases dramatically after trauma, and if they are lacking, they cannot synthesize proteins successfully even if they have enough calories. In short, amino acids in the human body through metabolism can play the following roles: ① synthesis of tissue proteins; ② into acids, hormones, antibodies, creatine and other ammonia-containing substances; ③ into carbohydrates and fats; ④ oxidation into carbon dioxide and water and urea, producing energy. Therefore, the presence of amino acids in the human body not only provides an important raw material for the synthesis of proteins, but also for the promotion of growth, normal metabolism, and maintenance of life provides the material basis. If the human body lacks or reduces one of them, the normal life metabolism of the human body will be impaired, and even lead to the occurrence of various diseases or the termination of life activities. From this, we can see that the amino acids in the human body life activities appear to be how much need.
Second, the status and role of food nutrition
Human beings in order to survive the need to ingest food, in order to maintain the normal physiology of the antibody, biochemistry, immune function, as well as growth, metabolism, and other life activities, food in the body through digestion, absorption, metabolism, and to promote the antibody growth, development, wisdom, health, anti-disease, prolonging the life of a comprehensive process known as nutrition. The active ingredients in food are called nutrients.
As the most basic substances that constitute the human body's proteins, lipids, carbohydrates, inorganic salts (i.e., minerals, including macronutrients and trace elements), vitamins, water and dietary fiber, but also nutrients needed by the body. They have their own unique nutritional function in the body, but in the metabolic process and closely linked, *** with the participation, promote and regulate life activities. The body through the food and the outside world, to maintain the relative constancy of the inner environment, and to complete the unity and balance of the internal and external environment.
What is the role of amino acids in these nutrients?
1. Protein digestion and absorption in the body is accomplished through amino acids
As the first element of nutrition in the body of protein, its role in food nutrition is obvious, but it can not be utilized directly in the body, but through the amino acids into small molecules after being utilized. That is, it is not directly absorbed by the body in the gastrointestinal tract of the human body, but in the gastrointestinal tract after a variety of digestive enzymes, high molecular proteins are broken down into low molecules of polypeptides or amino acids, which are absorbed in the small intestine and enter the liver along the hepatic portal vein. One part of the amino acids undergoes decomposition or synthesis of proteins in the liver; the other part of the amino acids continues to be distributed to various tissues and organs along with the bloodstream, and is left to be selected for the synthesis of a variety of tissue-specific proteins. Under normal circumstances, amino acids enter the bloodstream at a rate almost equal to their rate of output, so the amino acid content of the blood of normal people is fairly constant. For example, in terms of amino nitrogen, the content is 4-6 milligrams per 100 milliliters of plasma and 6.5-9.6 milligrams per 100 milliliters of blood cells. After a full meal of protein, a large number of amino acids are absorbed, the amino acid level in the blood is temporarily elevated, and after 6-7 hours, the content returns to normal. This indicates that amino acid metabolism in the body is in dynamic balance, with blood amino acids as its balance hub, and the liver is an important regulator of blood amino acids. Therefore, food proteins are digested and decomposed into amino acids, which are absorbed by the body, and the antibodies use these amino acids to synthesize their own proteins. The body's need for protein is actually the need for amino acids.
2. Nitrogen balance
When the quality and quantity of protein in the daily diet is appropriate, the amount of nitrogen ingested is equal to the amount of nitrogen excreted by the feces, urine and skin, which is called the total nitrogen balance. In fact, it is the balance between the constant synthesis and decomposition of proteins and amino acids. Normal people should keep the daily intake of protein within a certain range, sudden increase or decrease in intake, the body can still regulate the metabolism of protein to maintain nitrogen balance. If we eat too much protein, beyond the body's ability to regulate, the balance mechanism will be destroyed. Do not eat protein, the body still tissue protein decomposition, negative nitrogen balance continues to appear, if you do not take timely measures to correct, will eventually lead to the death of the antibody.
3. Transformation into sugar or fat
Amino acid catabolism produces a-keto acid, with different characteristics, the metabolic pathway of sugar or lipid metabolism. a-keto acid can be synthesized into new amino acids, or transformed into sugar or fat, or into the tricarboxylic acid cycle oxidation and decomposition of CO2 and H2O, and release of energy. energy.
4. Involved in the composition of enzymes, hormones, some vitamins
Enzymes are chemically proteins (composed of amino acid molecules), such as amylase, pepsin, cholinesterase, carbonic anhydrase, aminotransferase and so on. Nitrogen-containing hormones are composed of proteins or their derivatives, such as growth hormone, thyroid-stimulating hormone, adrenaline, insulin, and enteric fluid-stimulating hormone. There are vitamins that are transformed from amino acids or exist in combination with proteins. Enzymes, hormones and vitamins play a very important role in regulating physiological functions and catalyzing metabolic processes.
5. Essential amino acid requirements
Essential amino acid requirements for adults is about 20% of the protein requirements, -37%.
Three, in the application of medical
Amino acids in medicine is mainly used to prepare compound amino acid infusion, but also used as therapeutic drugs and for the synthesis of peptide drugs. At present, there are more than 100 kinds of amino acids used as drugs, including 20 kinds of amino acids that constitute proteins and more than 100 kinds of amino acids that constitute non-proteins.
The compound preparation composed of many kinds of amino acids occupies a very important position in the modern intravenous nutrition infusion and "elemental diet" therapy, which plays an active role in maintaining the nutrition of the critically ill patients and saving their lives, and has become one of the indispensable medicinal varieties in modern medical treatment.
Glutamic acid, arginine, aspartic acid, cystine, L-dopa and other amino acids work alone to treat a number of diseases, mainly used in the treatment of liver diseases, digestive diseases, cerebral diseases, cardiovascular diseases, respiratory diseases, as well as used to improve muscle vitality, pediatric nutrition and detoxification. In addition amino acid derivatives have shown promise in cancer treatment.
Four, the relationship with aging
Elderly people if the lack of protein in the body to decompose more and slower synthesis. Therefore, generally speaking, the elderly need more protein than young adults, and the demand for methionine, lysine is also higher than young adults. 60 years old and above should be consumed every day about 70 grams of protein, and the requirements of the protein contains essential amino acids complete and appropriate ratio, so that high-quality proteins, prolonged life.
Here are the benefits and drawbacks of chocolate:
Benefits:Chocolate Pharmacology
Chocolate contains more than 300 known chemical substances. Scientists have been analyzing and experimenting with each of these substances for hundreds of years, and have continued to discover and prove the pharmacological effects of chocolate and its various components on the human body.
Chocolate is a natural guard against heart disease
Chocolate is rich in polyphenol complexes, which play a considerable role in preventing the oxidation or accumulation of fatty substances in human arteries.
Coronary heart disease, the main condition of heart disease, is usually caused by cardiovascular obstruction due to oxidation of the fatty substance LDL (low-density lipoprotein) in the body's blood veins and the formation of obstructions.
The phenol complex of chocolate not only prevents the fat of chocolate itself from decaying and becoming acidic, but also can be absorbed into the blood vessels quickly after being ingested into the human body, and the antioxidant content in the blood increases significantly, and soon plays a positive role as a powerful antioxidant to prevent the oxidation of LDL and inhibit the activity of platelets in the blood vessels. These native substances play an important role in keeping blood flowing through human blood vessels.
Nutritionists have shown that these natural antioxidant phenol complexes are found in plant foods such as fruits, vegetables, red wine and tea.
Strawberries are the most antioxidant-rich of all fruits, however, chocolate contains eight times more antioxidants than strawberries.
Fifty grams (one tael) of chocolate contains about the same amount of antioxidants as 150 grams (three tael) of good red wine.
Chocolate has the effect of inhibiting depression and making people feel euphoric
Bad: Eating too much is easy to make people fat, resulting in too much food fat, there will be indigestion, gastrointestinal discomfort, etc.