The basic unit of protein is amino acids, which form peptide chains through dehydration and condensation. A protein is a biomacromolecule composed of one or more polypeptide chains. Each polypeptide chain has between 20 and hundreds of amino acid residues; various amino acid residues are arranged in a certain order. The organelles that produce proteins are ribosomes. Protein is the material basis of life. Without protein, there is no life. Therefore, it is a substance closely related to life and various forms of life activities. Every cell and all important components in the body have proteins involved.
Protein accounts for 16.3% of human body weight, that is, a 60kg adult has about 9.8kg of protein in his body. There are many types of proteins in the human body, with different properties and functions, but they are all composed of more than 20 amino acids in different proportions, and are continuously metabolized and renewed in the body.
Proteins The ingested proteins are digested and decomposed into amino acids in the body. After absorption, they are mainly used in the body to recombine human proteins in a certain proportion. At the same time, new proteins are constantly being metabolized and decomposed, and they are always in dynamic balance. Therefore, the quality and quantity of food protein and the ratio of various amino acids are related to the amount of protein synthesis in the human body, especially the growth and development of adolescents, the eugenics and eugenics of pregnant women, and the health and longevity of the elderly. close relationship.
1 gram of protein produces 4 kilocalories of energy. There are 20 kinds of amino acids that make up human protein. Among them, 9 kinds are essential amino acids. Essential amino acids refer to amino acids that the human body cannot synthesize and must be obtained directly from food. The nine amino acids are: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine and histidine.
Protein is divided into plant protein and animal protein. Animal protein has good quality and high utilization rate, but it is also rich in saturated fatty acids and cholesterol. The utilization rate of vegetable protein is low (except for soy protein), but the content of saturated fatty acids and cholesterol is relatively low. Excessive intake of animal protein is harmful to people, can cause obesity, or accelerate the loss of calcium and produce osteoporosis. Insufficient animal protein intake can cause malnutrition.
High-quality protein refers to eggs, milk, meat, fish, etc. in animal protein, and soy protein. Soybeans and milk are rich in high-quality protein, and all kinds of people should be strongly encouraged to increase the intake of milk and soybeans and their products. Rice and flour contain vegetable protein. The nutritional value of its protein alone is relatively low. Meat and soy protein can be added to make up. This is called protein complementation.
Protein physiological function
1. Construct human body: Protein is the material basis of all life, an important part of body cells, and the main raw material for human tissue renewal and repair. Every tissue of the human body: hair, skin, muscles, bones, internal organs, brain, blood, nerves, endocrine, etc. are all made up of protein, so the diet makes the person itself. Protein is very important for human growth and development. For example, the characteristic of brain development is the completion of cell proliferation at one time, and the growth of human brain cells has two peak periods. The first is when the fetus is three months old; the second is from birth to one year old, especially the 0-6 month old baby is a period of violent growth of brain cells. By the age of one year, the proliferation of brain cells has basically been completed, and the number has reached 9/10 of humans. Therefore, children aged 0 to 1 have special requirements on protein intake, which is particularly important for children's intellectual development.
2. Repairing human tissues: The human body is composed of tens of trillions of cells. Cells can be said to be the smallest unit of life. They are in the metabolic process of aging, death, and rebirth. For example, the epidermis of young people is renewed every 28 days, and the gastric mucosa should be completely renewed in two to three days. Therefore, if a person's protein intake, absorption and utilization are very good, then the skin is shiny and elastic. On the contrary, people are often in a sub-health state. After tissue damage, including trauma, can not be repaired in time and with high quality, it will accelerate the decline of the body.
3. Maintain the body's normal metabolism and the transport of various substances in the body: carrier proteins are essential to maintain the normal life activities of the human body. Can carry various substances in the body. For example, hemoglobin-transports oxygen (red blood cell renewal rate of 2.5 million per second), lipoprotein-transports fat, receptors on cell membranes, and transport proteins.
4. Albumin: Maintain the balance of osmotic pressure and body fluid balance in the body.
5. Maintain the acid-base balance of body fluids.
6. Immune cells and immune proteins: white blood cells, lymphocytes, macrophages, antibodies (immunoglobulins), complement, interferon, etc. Updated every seven days. When the protein is sufficient, this force is very strong, and when needed, it can be increased by a factor of 100 within a few hours.
7. Various enzymes that constitute the necessary catalytic and regulatory functions of the human body: The human body has thousands of enzymes, each of which can only participate in one biochemical reaction. Human cells undergo more than 100 biochemical reactions per minute. Enzymes can promote the digestion, absorption and utilization of food. If there are enough enzymes, the reaction will proceed smoothly and quickly, and people will be full of energy and not easy to get sick. Otherwise, the reaction becomes slow or blocked.
8. The main raw material of hormone: it can regulate the physiological activity of various organs in the body. Insulin is synthesized from 51 amino acid molecules. Auxin is synthesized from 191 amino acid molecules.
9. Constitute the neurotransmitters acetylcholine, serotonin, etc .: maintain the normal functions of the nervous system: taste, vision and memory.
10. Collagen: It accounts for 1/3 of the body's protein, generates connective tissue, and constitutes the body's skeleton. Such as bones, blood vessels, ligaments, etc., determine the elasticity of the skin and protect the brain (among the brain cells, a large part are collagen cells, and form a blood brain barrier to protect the brain)
11. Provide thermal energy.
In 1927, JBSummer proved that the enzyme is a protein. Then, in the 1950s, JBSummermi made a major discovery when describing the amino acid sequence of insulin. Other studies have shown the interrelationship between DNA, RNA and proteins. In 1953, F. Crick and J. Watson described the molecular structure of DNA. Scientists have gradually elucidated how cells build specific proteins with specific amino acid sequences.
The protein was discovered by Dutch scientist Gerrit in 1838. He observed that living things cannot survive without proteins. Protein is an extremely important high molecular organic substance in the organism, accounting for 54% of the human body's dry weight. Proteins are mainly composed of amino acids, and various types of proteins are composed due to the different arrangement of amino acids. There are estimated to be more than 100,000 proteins in the human body. Life is an advanced form of material movement. This movement is achieved through protein, so protein has extremely important biological significance. Proteins are indispensable for all life activities such as human growth, development, exercise, genetics, and reproduction. Protein is needed for life movement, and protein is also inseparable.
Some physiologically active substances in the body such as amines, neurotransmitters, peptide hormones, antibodies, enzymes, nucleoproteins, and proteins that act as â€œcarriersâ€ on cell membranes and blood are inseparable from proteins. Proteins regulate physiological functions , Maintaining metabolism plays an extremely important role. The composition of muscles in the human movement system and the metabolism of muscles during contraction, work, and completion of actions are all related to protein. Without protein, physical exercise is impossible to talk about. In biology, a protein is interpreted as a peptide formed by connecting amino acids by peptide bonds, and then a substance formed by connecting the peptides. It is easy to understand that it is the scaffold and main substance that constitutes human tissues and organs. It plays an important role in human life activities. It can be said that there is no life activity without protein. Protein in the daily diet is mainly found in lean meat, eggs, beans and fish.
In the absence of protein, adults will lose muscle weight, their body's immunity will decline, and anemia will occur. In severe cases, edema will occur. Minors have stunted growth and development, anemia, poor mental development, and poor vision. Protein cannot be stored in the body, and the body cannot absorb it. Excessive intake of protein will cause protein poisoning or even death due to metabolic disorders.
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