First, the basic substance that constitutes the human body is the material basis of life.
1. constitutes one of the most basic substances in the human body.
Protein, lipids, carbohydrates, inorganic salts, vitamins, water and dietary fiber are the most basic substances that constitute the human body.
As the basic unit of protein molecule, amino acid is undoubtedly one of the most basic substances in human body.
There are more than 20 kinds of amino acids that make up the human body, namely: tryptophan, methionine, threonine, valine, lysine, histidine, leucine, isoleucine, alanine, phenylalanine, cystine, cysteine, arginine, glycine, serine, tyrosine and 3.5. Diiodotyrosine, glutamic acid, aspartic acid, proline, hydroxyproline, arginine, citrulline, Ukraine. These amino acids exist in nature and can be synthesized in plants, but the human body cannot synthesize them all. Eight of them are not synthesized by human body and must be provided by food, which are called "essential amino acids". These eight essential amino acids are tryptophan, threonine, methionine, valine, lysine, leucine, isoleucine and phenylalanine. Others are "nonessential amino acids". Histidine can be synthesized in human body, but its synthesis speed can not meet the needs of the body, and some people list it as "essential amino acid". Cystine, tyrosine, arginine, serine and glycine are classified as "semi-essential amino acids" because they can be synthesized in vivo, but their synthetic raw materials are all essential amino acids. Cystine can replace 80% ~ 90% of methionine and tyrosine can replace 70% ~ 75% of phenylalanine to play the role of essential amino acids. For example, according to its metabolic pathway in the body, it can be divided into "ketogenic amino acids" and "glycogenic amino acids"; According to its chemical properties, it can be divided into neutral amino acids, acidic amino acids and basic amino acids, most of which are neutral.
2. Material basis of life metabolism
The emergence, existence and extinction of life are all related to protein, as Engels said: "protein is the material basis of life, and life is a form of existence in protein." If the human body lacks protein, its physique will be reduced, its development will be delayed, its resistance will be weakened, anemia will be weak, and edema will be formed in severe cases, even life-threatening. Once protein is lost, life will cease to exist, so some people call protein "the carrier of life". Can be said to be the first element of life.
The basic unit of protein is amino acid. If the human body lacks any essential amino acids, it will lead to abnormal physiological function, affect the normal metabolism of antibodies and eventually lead to diseases. Similarly, if the human body lacks some non-essential amino acids, there will also be disorder of antibody metabolism. Arginine and citrulline are very important for the formation of urea. Insufficient intake of cystine will cause insulin decrease and blood sugar increase. For example, the demand for cystine and arginine has greatly increased after trauma. Without it, even if the heat energy is sufficient, protein can't be successfully synthesized. In a word, amino acids can play the following roles in human body through metabolism: ① synthesis of tissue protein; (2) into acid, hormone, antibody, creatine and other ammonia-containing substances; (3) into carbohydrates and fats; ④ Oxidation into carbon dioxide, water and urea to generate energy. Therefore, the existence of amino acids in human body not only provides important raw materials for the synthesis of protein, but also provides a material basis for promoting growth, normal metabolism and maintaining life. If the human body lacks or reduces one of them, the normal life metabolism of the human body will be hindered, and even various diseases or life activities will be terminated. This shows how many amino acids are needed for human life activities.
Second, the position and role in food nutrition
In order to survive, human beings must eat food to maintain the normal physiological, biochemical and immune functions of antibodies, as well as life activities such as growth, development and metabolism. The comprehensive process of food being digested, absorbed and metabolized in the body, promoting antibody growth and development, improving intelligence and physique, resisting aging, preventing diseases and prolonging life is called nutrition. The effective ingredients in food are called nutrients.
Protein, lipids, carbohydrates, inorganic salts (that is, minerals, which contain a large number of elements and trace elements), vitamins, water and dietary fiber, which constitute the most basic substances of the human body and are also nutrients needed by the human body. They have their own unique nutritional functions in the body, but they are closely related in the process of metabolism, participating, promoting and regulating life activities together. The body communicates with the outside world through food, keeping the internal environment relatively constant, and completing the unity and balance of the internal and external environment.
What role do amino acids play in these nutrients?
1. The digestion and absorption of protein in the body is completed by amino acids.
Protein, as the first nutrient element in the body, plays an obvious role in food nutrition, but it can't be directly used in the human body, but can be used by becoming small molecules of amino acids. That is, it is not directly absorbed by the human body in the gastrointestinal tract, but is decomposed into low molecular weight peptides or amino acids by various digestive enzymes in the gastrointestinal tract, and then absorbed in the small intestine and enters the liver along the hepatic portal vein. Some amino acids are decomposed or synthesized into protein in the liver; Another part of amino acids continue to distribute to various tissues and organs with blood, and can freely choose to synthesize various specific tissue proteins. Under normal circumstances, the speed of amino acids entering the blood is almost equal to its output speed, so the content of amino acids in normal people's blood is quite constant. If calculated by amino nitrogen, the content is 4-6 mg per 100 ml of plasma and 6.5-9.6 mg per 100 ml of blood cells. After a full meal in protein, a large number of amino acids were absorbed, and the level of amino acids in blood temporarily increased, and the content returned to normal after 6-7 hours. It shows that amino acid metabolism in the body is in a dynamic balance, with blood amino acids as its balance hub, and liver is an important regulator of blood amino acids. Therefore, food protein is digested and decomposed into amino acids and then absorbed by human body, and antibodies use these amino acids to synthesize their own protein. What the human body needs for protein is actually the need for amino acids.
2. Play the role of nitrogen balance
When the quality and quantity of protein in daily diet are appropriate, the nitrogen intake is equal to the nitrogen discharged from feces, urine and skin, which is called the total balance of nitrogen. In fact, it is the balance of continuous synthesis and decomposition between protein and amino acids. Normal people's daily intake of protein should be kept within a certain range. When the intake suddenly increases or decreases, the body can still regulate the metabolism of protein and maintain the nitrogen balance. Excessive intake of protein, beyond the body's regulatory capacity, will destroy the balance mechanism. If you don't eat protein at all, the tissue proteins in your body will still decompose and negative nitrogen balance will continue to appear. If measures are not taken to correct it in time, the antibody will eventually die.
Step 3 turn into sugar or fat
α -keto acids produced by amino acid catabolism are metabolized along different sugar or fat metabolic pathways. α-keto acids can be synthesized into new amino acids, or converted into sugar or fat, or decomposed into CO2 and H2O through cyclic oxidation of tricarboxylic acid, releasing energy.
4. Participate in the formation of enzymes, hormones and some vitamins.
The chemical essence of enzymes is protein (amino acid molecular composition), such as amylase, pepsin, cholinesterase, carbonic anhydrase, transaminase, etc. The nitrogen-containing hormone is protein or its derivatives, such as growth hormone, thyroid stimulating hormone, adrenaline, insulin, intestinal juice stimulating hormone, etc. Some vitamins are converted from amino acids or exist in combination with protein. Enzymes, hormones and vitamins play a very important role in regulating physiological functions and catalyzing metabolism.
5. The demand for essential amino acids in human body
Adults' demand for essential amino acids is about 20%-37% of that of protein.
Third, the application in medical treatment.
Amino acids are mainly used to prepare compound amino acid infusion in medicine, and also used as therapeutic drugs and synthetic peptides. At present, there are more than 100 kinds of amino acids used as drugs, including 20 kinds of amino acids that constitute protein and more than 100 kinds of amino acids that constitute non-protein.
Compound preparation composed of various amino acids plays a very important role in modern intravenous nutrition infusion and "element diet" therapy. It plays an active role in maintaining the nutrition of critically ill patients and saving their lives, and has become one of the indispensable medical varieties in modern medicine.
Amino acids such as glutamic acid, arginine, aspartic acid, cystine and levodopa can be used alone to treat some diseases, mainly for treating liver diseases, digestive tract diseases, encephalopathy, cardiovascular diseases and respiratory diseases, as well as improving muscle vitality, pediatric nutrition and detoxification. In addition, amino acid derivatives are also promising in cancer treatment.
Fourth, the relationship with aging.
If the elderly lack protein, they will decompose more and synthesize more slowly. Therefore, generally speaking, the elderly need more protein than young adults, and the demand for methionine and lysine is also higher than young adults. People over the age of 60 should consume about 70g of protein every day, and it is required that protein contains all kinds of essential amino acids in proper proportion, so as to achieve high-quality protein and prolong life.
The following are the advantages and disadvantages of chocolate:
Benefits: knowledge of chocolate pharmacology
Chocolate contains more than 300 known chemicals. For hundreds of years, scientists have analyzed and experimented with these substances one by one, and in the process, they have continuously discovered and proved the vivid pharmacological effects of various components of chocolate on human body.
Chocolate is a natural guardian against heart disease.
Chocolate is rich in multi-source phenolic compounds, which plays a considerable role in preventing the oxidation or accumulation of fatty substances in human arteries.
The main symptom of heart disease is coronary heart disease, which is usually caused by the oxidation of LDL (low concentration lipoprotein) in human blood, thus causing cardiovascular obstruction.
Phenolic compounds in chocolate can not only prevent the fat in chocolate from rotting and turning sour, but also be quickly absorbed by blood vessels after eating into human body, and the antioxidant components in blood are obviously increased, which quickly exerts a powerful antioxidant effect, prevents LDL oxidation and inhibits platelet activity in blood vessels. These subcomponents play an important role in maintaining smooth blood flow in human blood vessels.
Nutritionists have proved that fruits, vegetables, red wine, tea and other plant foods contain such natural antioxidant phenolic compounds.
Strawberry has the strongest antioxidant capacity among fruits, but the antioxidant content of chocolate is 8 times higher than that of strawberry.
50 grams (one or two) of chocolate and 150 grams (three or two) of fine red wine are basically the same.
Chocolate can suppress depression and make people feel happy.
Disadvantages: eating too much can easily make people fat, leading to excessive food fat, indigestion, gastrointestinal discomfort and so on.