What role do proteins play in human life? Proteins and their biological role for our health
Proteins are complex organic compounds, consisting of amino acids (more than 80), of which 22 are the most common in foods. Proteins perform many vital functions important functions in the human body:
- serve as material for the construction of cells, tissues and organs, the formation of enzymes and most hormones, hemoglobin and other compounds;
- form compounds that provide immunity to infections;
- participate in the process of digestion of fats, carbohydrates, minerals and vitamins.
Unlike fats and carbohydrates, proteins do not accumulate in reserve and are not formed from other nutrients, being an indispensable part of food. With a lack of proteins, serious disruptions to the functioning of the glands occur. internal secretion, blood composition, weakened mental activity, slower growth and development of children, decreased resistance to infections. As a source of energy, proteins are of secondary importance, since they can be replaced by fats and carbohydrates.
In the human body, proteins are formed continuously from amino acids supplied with food. There are two groups of amino acids:
- essential amino acids (lysine, tryptophan, methionine, leucine, isoleucine, valine, threonine, phenyl-alanine) are not synthesized in the body and must be mandatory come with food. They are found mainly in products of animal origin;
- nonessential amino acids (arginine, cystine, tyrosine, alan im and others), which are synthesized in the human body from other amino acids.
Depending on the amino acid composition secrete complete (containing all 8 essential amino acids) and incomplete proteins. The source of the former is meat, fish, poultry, eggs and dairy products. Plant food contains mainly incomplete proteins.
When organizing meals, you should keep in mind that more than 90% of amino acids are absorbed from animal proteins in the intestines, and 60-80% from plant foods.
The proteins of dairy products and fish are digested most quickly, then meat (beef faster than pork and lamb), then bread and cereals, and proteins faster wheat bread from premium flour and semolina. The latter has great importance For therapeutic diets, but not for feeding a healthy person.
A balanced diet involves a combination of animals and plant products, improving the balance of amino acids. A long-term excess of protein in the diet is harmful, leading to overload of the liver and kidneys with its breakdown products, overstrain of the secretory function of the digestive apparatus, increased putrefactive processes in the intestines, accumulation of nitrogen metabolism products with a shift in the acid-base state of the body to the acidic side. Therefore, in case of kidney and liver failure, gout and some other diseases, protein consumption is limited or even temporarily eliminated.
Proteins, like vitamins and others useful material, is an integral part of the healthy functioning of our body
Most of our diseases are related to poor nutrition, in particular with high protein intake. Experts never tire of repeating that our body needs a balanced diet. Excluding some product from our diet can lead to microelements, which in turn leads to disruption of the body.
Most often, people underestimate the role of proper nutrition in the functioning of our body. According to a sociological survey, it became known that 50% (of those surveyed) do nothing to maintain their health.
Squirrels playing important role in the formation of tissues (organs, muscles, etc.), they are needed for the synthesis of hormones, and are also necessary for the formation of enzymes. The transmission of necessary information from one cell to another through the nervous system is also associated with proteins. Proteins help in the process of blood clotting, DNA represents protein molecules, and proteins also participate in the body’s energy processes (1g of protein produces 4 kcal of energy).
From this we can conclude that proteins are involved (directly or indirectly) in most of the processes that occur in our body. If there is a lack of proteins in the body, then all of the above processes will suffer.
Process of protein digestion happens with at different speeds. Proteins obtained by the body from fish or dairy products are digested the fastest, followed by proteins obtained from meat products. Proteins are digested more slowly plant origin.
What proteins should you give preference to? Nutritionists say that to maintain normal functioning organism in the menu must be included 30% plant proteins and 70% animal proteins. These data should only be changed if you have any pathology: for example, when renal pathology preference should be given to proteins of plant origin.
The surrounding climate also plays an important role in the required amount of proteins. For example, vegetarians from Asia are quite healthy when daily use 30-40g of protein, while Eskimos consume 200-300g of protein.
In my own way chemical composition proteins can be divided into complete and incomplete. To determine the usefulness of proteins, the presence of essential amino acids is considered, since it can synthesize all the rest itself. Complete proteins contain all the essential amino acids in the quantities needed by the body.
Animal proteins have a full set of essential amino acids (meat, fish, eggs and milk).
Plant based proteins are considered incomplete, with the exception of legumes. Beans contain the same amount of proteins as animal products.
For the full functioning of the body proteins of animal origin are necessary, as they are absorbed by 94-97%. However, this does not mean that you should not include plant proteins in your menu. For full growth and development of the body, a balance between animal and plant proteins is necessary.
Proteins play an extremely important role in human nutrition, since they are the main integral part cells of all organs and tissues. Everything is closely related to proteins life processes: metabolism, contractility, irritability, ability to grow, reproduce and even highest form movement of matter - thinking. By binding significant quantities, proteins form dense colloidal structures characteristic of our body. According to the definition of F. Engels, “life is a way of existence of protein bodies, the essential point of which is the constant exchange with the external nature surrounding them, and with the cessation of this metabolism, life also ceases, which leads to the decomposition of the protein.”
Main purpose of food proteins- this is the construction of new cells and tissues that ensure the development of young growing organisms. IN mature age When the growth processes are already completely completed, there remains a need for the regeneration of worn-out, obsolete cells. For this purpose, protein is required, and in proportion to the wear and tear of the tissues. It has been established that the higher muscle load, the greater the need for regeneration and, accordingly, for protein.
Protein intake is also necessary to maintain the constancy of specific body proteins, which are special value. These perform subtle and complex functions in the body; they are part of hormones, enzymes, antibodies and other formations involved in the most important biochemical processes life activity. The quantity and composition of specific proteins in the body are maintained at a constant level through use.
Proteins are complex nitrogen-containing biopolymers, the monomers of which are α-amino acids. The molecular weight of proteins varies from 6000 to 1,000,000 or more.
The amino acid composition of different proteins is different.
It is a criterion for the biological value of protein. In their structure, amino acids are organic compounds containing two functional groups: carboxyl (-COOH-), which determines acid properties molecules, and an amino group (-NH²-), which gives them basic properties.
Among huge amount There are 20 natural amino acids in food proteins: lysine, threonine, glycine (glycocol), alanine, serine, methionine, cystine, valine, leucine, isoleucine, glutamic acid, glutamine, aspartic acid, asparagine, arginine, phenylalanine, tyrosine, histidine, tryptophan, proline.
Food proteins are divided into simple (proteins) and complex (proteids).
Simple proteins consist only of polypeptide chains; complex proteins contain, in addition to the protein molecule, a non-protein part (prosthetic group). Depending on the spatial structure, proteins are divided into globular (the molecules of which have a spherical, ellipsoidal or similar shape) and fibrillar (consisting of elongated filamentous molecules).
Simple globular proteins include albumins, globulins, prolamins and glutelins. Albumins and globulins make up the main part of milk proteins, egg white, serum proteins. Prolamins and glutelins belong to vegetable seed proteins, forming the bulk of gluten.
Plant proteins are characterized low content lysine, leucine, threonine, methionine and tryptophan and high content glutamic acid. Structural proteins (protenoids) are fibrillar proteins of animal origin that perform a supporting function in the body. They are insoluble in water and resistant to digestion digestive enzymes. These include keratins, elastin, collagen.
When boiled in water for a long time, collagen turns into water-soluble gelatin (glutin), which is used in the technology of preparing a number of meat, fish and other dishes. Collagen and elastin contain little sulfur-containing amino acids, keratin is rich in cystine.
Unlike other food proteins, collagen contains significant amount hydroxyproline and oxylysine. However, collagen lacks tryptophan. Complex proteins include nucleoproteins, lipoproteins, glycoproteins, chromoproteins, metalloproteins, and phosphoproteins.
Proteins perform several important functions in the human body.- plastic, catalytic, hormonal, specificity and transport function.
The most important function of food proteins is to provide the body with plastic material. Proteins are the main building material of the cell, its organelles and intercellular substance; along with phospholipids, they form the skeleton of all biological membranes cells are the main component of all, without exception, enzymes and a significant part of hormones.
Proteins are involved in the transport of oxygen, lipids, carbohydrates, some vitamins, hormones and other substances in the blood.
Specific carrier proteins transport various mineral salts and vitamins through the membranes of cells and subcellular structures. Proteins provide individual and species specificity underlying the manifestations of immunity and allergies. The human body is practically deprived of protein reserves. Their only source is food proteins, as a result of which they are considered essential components of the diet.
The amount of nitrogen entering the body with food is usually equal to the amount excreted from the body (with urine, feces, sweat, exfoliating epidermis, hair, nails), i.e., a state of nitrogen balance is maintained.
Positive nitrogen balance occurs in children in connection with the growth process, as well as in those recovering after serious illnesses. A negative nitrogen balance occurs when the processes of protein catabolism predominate over the processes of synthesis (complete or partial starvation, consumption of low-protein diets, anorexia, vomiting), as well as when the absorption of proteins in the digestive system is impaired or their increased breakdown due to diseases (tuberculosis, tumors, burn disease and etc.).
Proteins, when oxidized, make a certain contribution to the body's energy supply. When 1 g of protein is burned in the body, 16.7 kJ (4 kcal) of energy is released. During fasting, the use of body proteins as a source of energy increases significantly.
Proteins coming from food products V gastrointestinal tract, before being absorbed by the body, must first be broken down into amino acids in the digestive canal. Amino acids are then absorbed by the intestinal mucosa and through the system portal vein They enter first the liver, and then all other organs and tissues and are used for the synthesis of proteins in the human body.
Of the 20 amino acids in food, 8 (threonine, lysine, leucine, isoleucine, valine, phenylalanine, tryptophan, methionine) are not synthesized in the body and are therefore considered essential. For children under one year of age, histidine is also an essential amino acid.
A deficiency of any of the essential amino acids in the diet, as well as an imbalance in the amino acid composition, leads to disruption of protein synthesis and thereby contributes to the emergence of a number of pathological conditions. A deficiency of protein in food leads to the development protein deficiency.
Mild forms of protein deficiency may arise due to violations of the principles balanced nutrition, as well as in diseases accompanied by impaired digestion and absorption of proteins and amino acids in the digestive canal, increased catabolism of the body’s own proteins and other disorders of the metabolism of proteins and amino acids ( chronic colitis and enterocolitis, burn disease, extensive surgical interventions and injuries, malignant neoplasms and etc.).
Excessive protein intake causes increased work digestive system, activation of amino acid metabolism and urea synthesis processes, increases the load on excretory system, can lead to the formation in the digestive canal of products of their rotting and incomplete breakdown, which can cause intoxication.
1. Composition of protein molecules. Proteins are organic substances whose molecules include
carbon, hydrogen, oxygen and nitrogen, and sometimes sulfur and other chemicals
elements.
2. The structure of proteins. Proteins are macromolecules consisting
of tens or hundreds of amino acids. Variety of amino acids (about 20 types),
components of proteins.
3. Species specificity of proteins - differences in proteins,
included in organisms belonging to different species, determined by the number
amino acids, their diversity, sequence of compounds in molecules
squirrel. The specificity of proteins in different organisms of the same species is the reason
rejection of organs and tissues (tissue incompatibility) when transplanted from
one person to another.
4. Protein structure - complex configuration of molecules
proteins in space, supported by various chemical bonds -
ionic, hydrogen, covalent. Natural state of protein. Denaturation -
disruption of the structure of protein molecules under the influence of various factors -
heating, irradiation, chemical action. Examples of denaturation:
change in protein properties when boiling eggs, transition of protein from liquid to
hard when a spider builds its web.
5. The role of proteins in the body:
Catalytic. Proteins are catalysts that increase
speed chemical reactions in the cells of the body. Enzymes - biological
catalysts;
Structural. Proteins are elements of plasmatic
membranes, as well as cartilage, bones, feathers, nails, hair, all tissues and organs;
Energy. The ability of protein molecules to
oxidation with the release of energy necessary for the life of the body;
Contractile. Actin and myosin are proteins included in
composition of muscle fibers and ensuring their contraction due to the ability
molecules of these proteins to denaturation;
Motor. Movement of a number of single-celled organisms
organisms, as well as spermatozoa with the help of cilia and flagella, in the composition
which include proteins;
Transport. For example, hemoglobin is a protein that is part of
in the composition of red blood cells and ensuring the transfer of oxygen and carbon dioxide;
Storage. Accumulation of proteins in the body as
spare nutrients, for example in eggs, milk, plant seeds;
Protective. Antibodies, fibrinogen, thrombin - proteins,
involved in the development of immunity and blood clotting;
Regulatory. Hormones are substances that provide
along with nervous system humoral regulation of body functions. The role of the hormone
insulin in regulating blood sugar.
2. The biological significance of the reproduction of organisms. Reproduction methods.
1. Reproduction and its meaning.
Reproduction is the reproduction of similar organisms, which ensures
the existence of species for many millennia contributes to an increase
number of individuals of a species, continuity of life. Asexual, sexual and
vegetative reproduction of organisms.
2. Asexual reproduction is the most ancient method. IN
Asexuality involves one organism, while sexually most often involves
two individuals. In plants, asexual reproduction occurs with the help of a single spore.
specialized cell. Reproduction by spores of algae, mosses, horsetails,
mosses, ferns. The eruption of spores from plants, their germination and development from
them new daughter organisms under favorable conditions. The death of a huge number
disputes falling into unfavorable conditions. Low probability of occurrence
new organisms from spores, since they contain few nutrients and
the seedling absorbs them mainly from the environment.
3. Vegetative propagation - propagation of plants with
with the help of vegetative organs: aboveground or underground shoots, parts of the root,
leaf, tuber, bulb. Participation in vegetative reproduction of one organism
or parts thereof. The similarity of the daughter plant with the mother plant, since it
continues the development of the mother's body. Greater efficiency and
the spread of vegetative propagation in nature, since the daughter organism
is formed faster from a part of the mother than from a spore. Examples of vegetative
propagation: using rhizomes - lily of the valley, mint, wheatgrass, etc.; rooting
lower branches touching the soil (layers) - currants, wild grapes; mustache
Strawberries; bulbs - tulip, daffodil, crocus. Use of vegetative
propagation when growing cultivated plants: potatoes are propagated by tubers,
bulbs - onions and garlic, layering - currants and gooseberries, root
offspring - cherries, plums, cuttings - fruit trees.
4. Sexual reproduction. The essence of sexual reproduction
in the formation of reproductive cells (gametes), the fusion of the male reproductive cell
(sperm) and female (ovum) - fertilization and development of a new
daughter organism from a fertilized egg. Thanks to fertilization, obtaining
daughter organism with a more diverse set of chromosomes, which means with a more
various hereditary characteristics, as a result of which it may turn out to be
more adapted to the environment. The presence of sexual reproduction in
sexual process in plants in the process of their evolution, the appearance of the most complex
forms in seed plants.
5. Seed propagation occurs using seeds,
Vegetative propagation is also widespread). Sequence of stages
seed propagation: pollination - transfer of pollen to the stigma of the pistil, its
germination, the appearance by division of two sperm, their advancement into
ovule, then the fusion of one sperm with the egg, and the other with
secondary nucleus (in angiosperms). Formation of a seed from the ovule -
the embryo with a supply of nutrients, and from the walls of the ovary - the fruit. Seed -
the germ of a new plant, in favorable conditions it germinates at first
the seedling feeds on the nutrients from the seed, and then its roots
begin to absorb water and minerals from the soil, and the leaves begin to absorb carbon dioxide
gas from the air in sunlight. Independent life of a new plant.
Properties squirrel depend both on its composition and on the arrangement of amino acids in the molecule. Moreover, the order of amino acids in a protein molecule plays a very important role in the performance of their functions.
Amino acids, synthesized in our body, are called replaceable. Some amino acids are not formed in the human body - these are essential amino acids. Proteins containing the entire set of essential amino acids are biologically complete. They are found both in animal foods and in some food plants- soybeans, peas, beans.
If we accept value of milk proteins(it contains all essential amino acids) for 100, then biological value meat and fish can be expressed by the number 95, potatoes - 85, rye bread- 75, rice - 58, peas - 55, wheat - 50.
Everything must be supplied with food essential amino acids, a deficiency of at least one of them can lead to the death of the body, since each of the essential amino acids affects certain of its functions.
Great protein valueV not only in digestion, but also in all human life. Enzymes are built from proteins - biological catalysts that accelerate the course of chemical reactions occurring in the body.
And what meat food makes people irritable and cruel, by analogy with predatory animals, and also does not stand up to criticism. After all, as advocates of vegetarianism argue: “Herbivorous animals are distinguished by an easy-going disposition, even nature has not deprived them of strength and power. Take for example the elephant - it is powerful and kind, while lions are characterized by ferocity and bloodthirstiness.” Although zoological arguments, and we have already understood this, are much contradictory, it is not difficult to see that in these primitive reasoning, causes are replaced by consequences: it is not meat food that makes predators predatory, but people of a certain type aggressive and socially dangerous. According to this reasoning, it turns out that if a lion is fed with carrots, it will become quiet, like a rabbit, and a rabbit will go wild from meat. But for some reason it seems to me that both will die before they have time to get used to food that is unusual for them.
An uncompromising vegetarian, in order to get 50-70 g of fat, must eat 4-5 kg of plant products daily, and at least 70% of them should be oilseeds. Thus, partial and especially complete refusal from animal products today can also be considered as a kind of tribute to “fashionable” diets.
What protein is involved in formation muscle tissue , as if it goes without saying, but not everyone knows that he also participates in skeleton construction.
This is due to the fact that protein food helps the absorption of calcium, while a decrease in the level of protein in food impairs the absorption of this element by the intestinal mucosa. But more than 90% of calcium is concentrated in human bones: it is this element that gives strength to the skeleton. However, the functions of calcium in the body are not limited to this; it increases the excitability of the neuromuscular system, promotes blood clotting, reduces the permeability of the walls blood vessels. Calcium is involved in the work of the heart muscle, promotes the implementation therapeutic effect cardiac glycosides, stimulates liver function, activates the enzyme lipase. Therefore, protein foods enriched with calcium, especially milk and dairy products, are biologically more complete compared to foods of purely plant origin with a low calcium content.
Calcium deficiency in the body, provoked by the rejection of animal proteins, leads to a violation of a number of physiological functions, in particular, mental and physical performance, in children, bone formation is inhibited, and in adults, bones are resorbed.
The following historical example is very indicative in this regard.
In 1857, 8 years old Vanya Pavlov, future laureate Nobel Prize, fell from a high platform and after that began to fall seriously ill. Maybe the boy would not have survived if his godfather, the abbot of the suburban Trinity Monastery, had not taken him to his place. The old man knew healing power protein nutrition and therefore fed his godson eggs, milk and boiled chickens. In the mornings he did gymnastics with him, in the summer he made him swim, ride a horse, play gorodki, and in the winter he made him shovel snow and skate. The boy always and willingly helped the abbot tend the garden and vegetable garden. The abbot himself was distinguished by enviable health, which he confidently considered a consequence healthy eating. Later, Ivan Petrovich Pavlov wrote that indifference to food is imprudence, and more than once said that it was thanks to proper nutrition retained high performance, endurance and clarity of thought until his full 86 years.
A completely opposite metamorphosis occurred with another representative of the Russian intelligentsia, who decided to old age become a vegetarian. Unlike little Vanya, who was sick in childhood, little Levushka was an unusually healthy boy, and even in his mature years, while fighting near Sevastopol, Lev Nikolaevich did not complain about his health. Having retired and, according to V.I. Ulyanov-Lenin’s definition, becoming a “hardened man,” Tolstoy amazed those around him physical health, carrying water, riding a bicycle and skating at almost 80 years old. True, worldwide famous writer He stopped eating meat only in his old age after he saw the scene at the Tula slaughterhouse, when they began to tear off the skin from a fallen bull, and life was still beating in the huge body of the animal and large tears were rolling from his blood-stained eyes. Back in Yasnaya Polyana, Lev Nikolaevich, for purely moral reasons, completely abandoned meat and his appearance literally immediately began to change. This is what his wife Sofya Andreevna wrote 7 years before the writer’s death: “It’s so painful for me to see him suffering, weak, fading and oppressed in spirit and body. Take his head in both hands or kiss his emaciated hands with tender, careful caress, and he’ll look indifferently. Something is happening in him, what is he thinking?" The change that occurred with L.N. Tolstoy after switching from his usual mixed food to plant-based food is completely understandable and completely explainable.
Dietary protein deficiency negatively affected the functioning of his body. First of all, the nitrogen balance was disrupted, and protein breakdown began to prevail over its synthesis. Experiencing a lack of protein, the body began to “feed” on its own tissues. It is not surprising that seven years later, the final clouding of his mind led Tolstoy to death.
Protein deficiency in nutrition, it reduces the body’s resistance to infections, as the level of antibody formation decreases. The synthesis of other protective factors- lysozyme and interferon, which aggravates the course inflammatory processes. Reducing the intake of protein from food, or increasing its consumption in the body (in severe physical work or as a result of illness) causes protein deficiency. A severe form of protein deficiency is called kwashiorkor. This disease occurs more often in children. In Russia, kwashiorkor is not observed, but the disease is often found in developing countries Asia, Africa, Central and South America.
Lack of compensation squirrel in the body has an adverse effect on activity cardiovascular, respiratory and other systems. Lack of protein impairs appetite, which in turn reduces the influx of protein from food - a vicious circle arises.
In order to prevent this from happening, it is necessary to constantly introduce physiologically into the body. required amount protein with food.
