Water functions in biology. Transport

After reviewing the elements present in living organisms, we now turn to the compounds that these elements are included. And here we also discover the fundamental similarity between all living organisms. Most of all the organisms contain water - from 60 to 95% of the total mass of the body. In all organisms, we also find some simple organic compounds that play the role of "building blocks", which build larger molecules (Table 5.2). This will be discussed below.

Table 5.2. Chemical "Building Blocks" of Organic Compounds

Thus, a relatively small number of species of molecules gives the beginning of all the larger molecules and the structures of living cells. According to biologists, these few types of molecules could be synthesized in the "primary broth" (i.e. in concentrated solution chemical substances) In the World Ocean in the early stages of the Earth's existence, even before life appears on our planet (Section 24.1). Simple molecules are built in turn from even simpler inorganic molecules, namely from carbon dioxide, from nitrogen and water.

An important role of water

Without water, life on our planet could not exist. Water is important for living organisms is doubly, for it is not only the necessary component of living cells, but for many more habitats. We should therefore say a few words here about its chemical and physical properties.

These properties are rather unusual and are mainly associated with small sizes of water molecules, with the polarity of its molecules and with their ability to connect with each other hydrogen bonds. Under polarity, implies an uneven distribution of charges in the molecule. In the water, one end of the molecule carries a small positive charge, and the other is negative. Such a molecule is called dipolem. A more electrone-negative oxygen atom attracts electrons of hydrogen atoms. As a result, electrostatic interaction occurs between water molecules, and since the opposite charges are attracted, the molecules as it were to be "bonded" (Fig. 5.4). These interactions, weaker than ordinary ionic communications, are called hydrogen bonds. Given this feature of water, we can now proceed to the consideration of its properties that are important from a biological point of view.

Fig. 5.4. Hydrogen bond between two polar water molecules. Δ + - very small positive charge; Δ - - very little negative charge

Biological value of water

Water as a solvent. Water is an excellent solvent for polar substances. These include ionic compounds, such as salts that have charged particles (ions) dissociate (separated from each other) in water, when the substance dissolves (Fig. 5.5), as well as some non-ionic compounds, such as sugar and simple alcohols, The molecule of which there are charged (polar) groups (sugars and alcohols it is a group).

When the substance passes into the solution, its molecules or ions are able to move more freely and, accordingly, its reactivity increases. For this reason, in the cell, most of the chemical reactions occur in aqueous solutions. Non-polar substances, such as lipids, are not mixed with water and therefore can be separated by aqueous solutions into individual compartments, just as membranes are separated. Non-polar parts of molecules are repelled with water and in its presence are attracted to each other, as it happens, for example, when oil droplets merge into more large drops; In other words, non-polar molecules hydrophobic. Such hydrophobic interactions play an important role in ensuring the stability of membranes, as well as many protein molecules, nucleic acids and other subcellular structures.

Inherent in the water of the solvent properties also mean that water serves as a medium for transporting various substances. It performs this role in the blood, in the lymphatic and excretory systems, in the digestive tract and in the floem and xylene of plants.

Large heat capacity. The specific heat capacity of water is called the amount of heat in Joules, which is necessary to lift the temperature of 1 kg of water at 1 ° C. Water has a big heat capacity. This means that a significant increase in thermal energy causes only a relatively slight increase in its temperature. This phenomenon is explained by the fact that a significant part of this energy is spent on a break. hydrogen ties, limiting the mobility of water molecules, i.e., to overcoming it mentioned above "stickiness".

The high heat capacity of water minimizes the temperature changes occurring in it. Due to this, biochemical processes flow in a smaller temperature range, with a more constant speed and danger of the violation of these processes from sharp deviations of temperature threatens them not so much. Water serves for many habitat cells and organisms for which a rather significant consistency of conditions is characteristic.

Big heat evaporation. Hidden heat of evaporation (or relative hidden heat of evaporation) There is a measure of the amount of thermal energy, which is necessary to inform liquid to transition to steam, i.e. to overcome the molecular clutch forces in the liquid. Evaporation of water requires rather significant amounts of energy. This is due to the existence of hydrogen bonds between water molecules. It is precisely why the boiling point of water - substances with such small molecules - unusually high.

The energy required by water molecules for evaporation is drawn from their environment. Thus, evaporation is accompanied by cooling. This phenomenon is used in animals when sweating, with thermal shortness of mammals or some reptiles (for example, crocodiles), which are sitting with open mouth on the sun; It is possible that it plays a noticeable role in the cooling of transparency leaves.

Big melting heat. Hidden heat of melting (or relative hidden melting heat) is a measure of heat energy required for melting a solid (in our case - ice). Water for melting (melting) requires a relatively large amount of energy. Inversely: when freezing, water should give a large amount of thermal energy. This reduces the likelihood of freezing the contents of cells and the surrounding fluid. Ice crystals are especially destructive for living when they are formed inside the cells.

Density and behavior of water near the freezing point. The water density from +4 to 0 ° C is lowered, so the ice is lighter than water and in water is not sinking. Water is a single substance that has a larger density in a liquid state than in solid.

Since ice floats in water, it is formed when freezing first on its surface and only at the end in the bottom layers. If the frosting of the ponds went in the reverse order, from the bottom up, then in areas with a temperate or cold climate, life in freshwater reservoirs could not exist at all. The ice covers the thickness of water, as a blanket, which increases the chances of survival in the organisms living in the water. This is important in cold climate conditions and during the cold season, but, undoubtedly, it was a particularly important role in the ice age. Being on the surface, ice faster and melts. The fact that the layers of water, the temperature of which fell below 4 ° C, rise up, determines the mixing of water in large water bodies. Along with water, nutrients in it are circulated, thanks to which the reservoirs are populated by alive organisms to a greater depth.

Large surface tension and cohesion. Cugezzia is the grip of the physical body molecules with each other under the action of attraction forces. There is a surface tension on the surface of the liquid - the result of cohesion forces acting between molecules inwards. Due to the surface tension, the liquid tends to take such a form so that its surface area is minimal (ideally - the shape of the ball). Of all the liquids, the largest surface tension in the water. Significant cohesion characteristic of water molecules plays an important role in living cells, as well as when the water is moving along the vessels of xylems in plants (Section 14.4). Many small organisms benefit from surface tension: It allows them to hold on water or slide on its surface.

Water as a reagent. The biological value of water is determined by the fact that it is one of the necessary metabolites, i.e. it is involved in metabolic reactions. Water is used, for example, as a source of hydrogen in the process of photosynthesis (Section 9.4.2), and also involved in hydrolysis reactions.

Water and evolution process. The role of water for living organisms is reflected, in particular, in the fact that one of the main factors natural selectionaffecting the species is lack of water. To this topic, we already appealed to ch. 3 and 4, when they discussed the restrictions with which the propagation of some plants having moving gems. All terrestrial organisms are adapted to obtain and save water; In the extreme manifestations - in xerophytes, in the wilderness of animals, etc. - this kind of adaptation is presented with a true miracle of the "ingenuity" of nature. In tab. 5.3 Listed a number of important biological functions of water.

Table 5.3. Some important biological functions of water

All organisms have Provides maintenance of structures (high water content in protoplasm) Serves as a solvent and diffusion medium Participates in hydrolysis reactions Serves as a medium in which fertilization occurs Provides the distribution of seeds, weights and larval stages of aquatic organisms, as well as seeds of some land plants, such as coconut palm

In plants Determines OSMOS and TURGESSENTRATION (from which much depends on: growth (increase in cells), maintaining the structure, the movement of the mouth, etc.) Participates in photosynthesis Provides transpiration, as well as transport of inorganic ions and organic molecules Provides germination of seeds - swelling, separation of seed peel and further development

In animals Provides transport substances Determines the osorlagulation Promotes body cooling (sweating, thermal shortness) Serves as one of the components of the lubricant, for example in the joints Carries reference functions (hydrostatic skeleton) Performs protective function, for example, in tear fluid and mucus Promotes migration (sea currents)

Structure, properties and biological functions of water

Life on planet Earth originated in aquatic environment. No organism can do without water. Despite the simplicity chemical composition and buildings, water is one of the amazing compounds, has unique physicochemical properties and biological functions.

The water molecule (H 2 O) is a polar compound in which the electrophil oxygen atom attracts paired electrons from hydrogen atoms, acquiring a partial negative charge, while hydrogen atoms acquire partially positive charges. An important feature Water is the ability of its molecules to be combined into structural units due to the formation of hydrogen bonds between the varieme-charged atoms. Forming associates (Fig. 1) consist of several water molecules, in connection with this, the water formula would be more correct to write as (H 2 O) L, where p\u003d 2, 3, 4, 5. Hydrogen bonds are extremely important in the formation of the structures of biopolymers, supramolecular complexes, in metabolism.

J. Pimimatel and O. Mac-Clallan believes that in the chemistry of living systems, hydrogen relationship is as important as a carbon-carbon connection. What is hydrogen bond?

Fig. 1. Associate of water molecules (dots marked hydrogen bonds)

Hydrogen communications- This is the interaction of a hydrogen atom with a more electronegative atom, having a partially donor-acceptor, partially electrostatic character.
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Any chemical bond is characterized by the energy of its formation. By energy, hydrogen bond occupies an intermediate position between the covalent (200-400 kJ / mol) and ion chemical bonds and weak van der Waals interactions, being in the range of 12-30 kJ / mol.

The unusual water structure determines its unique physicochemical properties. All biochemical processes in the body flow in aquatic environment. Substances in aqueous solution, have an aqueous shell, which is formed as a result of the interaction of polar water molecules with charged groups of macromolecules or ions. The more such a shell, the better the substance is soluble.

In relation to water molecules or part of them are divided into hydrophilic (Water soluble) and hydrophobic (Water-resistant). Hydrophilicities are organic and inorganic compounds, dissociating on ions, biological monomers and biopolymers having polar groups. The hydrophobic contains a combination of molecules of which contain non-polar groups or chains (triacylglycerin, steroids, etc.). Molecules of some compounds contain both hydrophilic and hydrophobic groups; Such compounds are called amphilines (from Greek. amphy- Two way). These include fatty acids, phospholipids, etc.
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From the above, it follows that the water dipoles are capable of interacting not only among themselves, but ft with organic polar molecules and inorganic substanceslocalized in the cell cage. This process was the name of the hydration of substances.

Physico-chemical properties of water Determine its biological functions:

‣‣‣ Water is an excellent solvent.

‣‣‣ Water performs the function of the heat balance regulator of the body, since its heat capacity is significantly higher than the heat capacity of any biological substance. For this reason, water can last heat when changing the ambient temperature and transfer it to the distance.

‣‣‣ Water contributes to the preservation of intracellular pressure and cell shape (turgor).

‣‣‣ In definition biochemical processes, water acts as a substrate.

Water content in human bodydepends on age: the younger man, the higher the water content. The newborn water is 75% of the mass of the body, in children from 1 year to 10 years - 60-65%, and people over 50 are 50-55%. Inside the cells contain 2/3 of the total amount of water, extracellular water is 1/3. The required water content in the human body is maintained due to the receipt of it from outside (about 2 liters per day); About 0.3 l per day is formed in the process of decay of substances inside the body. Violation of the water balance in the cells of the body leads to severe consequences to the death of the cells. The cell functions depend on the total amount of intracellular and extracellular water, from the aqueous environment of macromolecules and subcellular structures.
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A sharp change in the content of water in the body leads to pathology.

Structure, properties and biological functions of water are concepts and types. Classification and features of the category "Structure, Properties and Biological Water Functions" 2017, 2018.

Each of us probably heard the phrase that the human body is more consisting of water. And how did you think that this is so? Why do you need such a large amount of liquid and in general what function does water in the body perform?

Properties

Water has the following properties:

• first of all, it is a good solvent (both for nutrients and toxic);
• fluidity;
• has high heat capacity and thermal conductivity;
• can evaporate;
• it is capable of hydrolyzing other substances (i.e. substances decompose under its action or split in it).

Thanks to these basic properties, water performs a number of functions in the body of each living being. Consider them in more detail.

Water functions in the body

The body of a person on average 75% consists of water. This ratio changes with age, unfortunately, towards the decrease.

Water, being the main component of all organism fluids, in particular blood, in which more than 90% is contained precisely, performs the following main functions:

• regulation of body temperature;
• excretion of slags, toxins and;
• transport of nutrients and oxygen;
• assimilation and digestion of food;
• transport function;
• depreciation of the joints and preventing their friction;
• maintenance of cell structures;
• protection of tissues and internal organs;
• improving metabolism.

Water functions in thermoregulation processes are to ensure a constant body temperature on cellular level by evaporation and sweating. Due to its ability to transfer a sufficiently large moisture, circulating in the human body, takes it where it is in surplus, and adds where it is not enough.

The depreciation functions of water in the body are provided by its large content in the synovial fluids of the joints. This prevents the friction of the joint surfaces during the loads and the work of the joints, and is also a specific protective buffer with possible drops and injuries.

Water performs the function of transport of the necessary compounds due to its thus, it can penetrate everywhere, even in intercellular spaces, delivering to organs and tissues the necessary and deriving their livelihoods.

The generally accepted is the fact that mental dehydration is directly dependent on the amount of fluid in directly depends not only by the decline, energy, the appearance of headaches and dizziness, but also with a decrease in working capacity, memory and the possibility of concentration on the necessary information.

Also, considering that with age, the amount of water as a component of the body decreases, scientists are assumed to be a certain relationship between the amount of liquid and the aging processes. Therefore, people of the older age group should particularly carefully approach the water diet.

IN last years The functions of water and the prevention of many diseases, including oncological ones, are increasingly marked. It is believed that the more fluid we use, the more it is excreted, and with it and the pathogenic organisms, the products of their livelihoods, toxins and which can potentially be a bridgehead for the development of cancer.

Thus, all water functions are important for the normal functioning of all organs and systems and for a comfortable and healthy lifestyle of a person.

The less water comes from the outside, the more it is accumulated inside. This means that if you are irregular and in insufficient quantities use liquid, then with its next arrival, the body delays water, keeping it as if about the reserve. Thus, a person not only personally exposes itself to a number of diseases, but also gains overweight.

The first signal that gives your body about the lack of water to them is all the well-known fatigue. If a long time does not refund the physiological loss of fluid, then the person begins to feel the lubrication in the joints and discomfort in the spine. The body accumulates toxins, immunity decreases, and the person becomes more susceptible to diseases, especially infectious.

Important!

Every day it is necessary to consume 1.5-2 liters of fluid. Regular reception of high-quality water will give you a feeling of tide of strength and cheerfulness, the processes of digestion will improve, stop disturbing headaches and other uncomfortable sensations. You will not only feel better, but also you will definitely look better.

Conclusion

The functions of water in the human body are diverse and numerous. Therefore, you should not neglect such an important component of your diet. Use water in the required quantities and be healthy!

... (Philipp Niethammer) was engaged in finding methods for detecting hydrogen peroxide in the body A on the existence of its immune functions I did not even guessed. The biologists have long known that hydrogen peroxide is a substance having a rather strong ... function hydrogen peroxide on the example of fish the group of scientists intends to now switch to studies like functions this compound in the human body - despite some genetic kinship of fish is still too far from man biology ...

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... , water is basic biological Liquid. It is not only an inert environment, it can also join the connection with other components of living matter. Water Plays and thermostatic role - supports the necessary body temperature. It exercises its large heat capacity in the event of a decrease in temperature and evaporation from the body surface when it overheated. Transport function water carried out ...

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Only for this you need to possess a big positive energy. Amazing composition of charged prayer frozen water. Normal water Freezes, and the molecules are folded in chaotic order. Charged water It has a clear structure in the form of various asterisks and patterns. Water put on the night under the column with classical music. As a result, different patterns were fixed depending on what ...

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Organism. We already talked about the fact that we need about 2-2.5 liters water daily. Part water Reimbursed from drinks, about 1.5 liters per day ( water, milk, fruit juices, tea, coffee, soup, etc.). A small part of the loss ... Kefir beat in a mixer. All these cocktails are good with the addition of ice cubes. And in conclusion I want to say that water Not only provides metabolism to maintain their balance, but also is a unique cleaner of our body. In addition to food ...

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After that, placed in the analyzer chamber. It was necessary in order for the part of the frozen water. "Mars presents to us surprises. One surprises is how the soil behaves in an open space. ... the top layer of the soil). However, scientists say that the presence of water Mars does not mean any life at all. The reason both in temperature and in the possible absence in this water nutrient carbon elements necessary for any organic shape ...

Water plays a crucial role in the life of cells and living organisms in general. In addition, it is included in their composition, for many organisms it is also habitat. The role of water in the cell is determined by its properties. These properties are rather unique and are mainly associated with the small size of water molecules, with the polarity of its molecules and with their ability to combine with each other hydrogen bonds.

Water molecules have a nonlinear spatial structure. Atoms in the water molecule are held by means polar covalent tieswhich bind one oxygen atom with two hydrogen atoms. The polarity of covalent bonds (i.e., the uneven distribution of charges) is explained in this case by the strong electronegativity of oxygen atoms relative to the hydrogen atom; Oxygen atom deducts electrons from general electronic pairs.

As a result, a partially negative charge occurs on an oxygen atom, and on hydrogen atoms - partially positive. Between the atoms of oxygen and hydrogen of neighboring molecules arise hydrogen bonds.

Due to the formation of hydrogen bonds of water molecules, it is one on the other, which causes its initial state under normal conditions.

Water is excellent solvent For polar substances, such as salts, sugars, alcohols, acids, etc. Substances are well soluble in water, called hydrophilic.

Absolutely non-polar substances like fat or oils water does not dissolve and is not mixed with them, since it cannot form hydrogen bonds with them. Insoluble in water substances are called hydrophobic.

Water has high specific heat capacity. For the breaking of hydrogen bonds holding water molecules, it is necessary to absorb a large amount of energy. This property ensures the maintenance of the thermal balance of the body with significant temperature differences in environment. In addition, water has high thermal conductivitythat allows the body to maintain the same temperature in all its volume.

Water also has high warm steam formation. The ability of molecules to determine a significant amount of heat, cooling the body. This property of water is used when sweating in mammals, thermal shortness of crocodiles and transpiration in plants, preventing overheating.

For water is characteristic exclusively high surface tension. This property is very important for adsorption processes, for the movement of solutions for tissues (blood circulation, up to and downward currents in the body of plants). Many small organisms benefit from surface tension for themselves: it allows them to hold on water or slide along its surface.

Biological functions of water

Transport. Water provides the movement of substances in the cell and the body, the absorption of substances and the elimination of metabolic products.

Metabolic. Water is a medium for all biochemical reactions in the cell. Her molecules participate in many chemical reactions, for example, in the formation or hydrolysis of polymers. In the process of photosynthesis, water is an electron donor and a source of hydrogen atoms. It is the source of free oxygen.

Structural. Cell cytoplasm contains from 60 to 95% water. In plants, water determines the cells of the cells, and some animals perform reference functions, being a hydrostatic skeleton (round and killed worms, Icharkin).

Water is involved in the formation of lubricating liquids (synovial in the joints of the vertebrate; pleural in the pleural cavity, pericardial in the window-shaped bag) and mucus (which facilitate the movement of substances by the intestines, create a wet medium on the mucous membranes of the respiratory tract). It is part of saliva, bile, tears, sperm, etc.

Mineral salts. Molecules of salts in aqueous solution are dissociated on cations and anions. The greatest value These have cations: K +, Na +, Ca 2+, Mg 2+ and anions: Cl -, H 2 PO 4 -, HPO 4 2-, HCO 3 -, NO 3 -, SO 4 2-. It is essential not only content, but also the ratio of ions in the cell.

The difference between the number of cations and anions on the surface and inside the cell provides the occurrence of the potential of action, which underlies the nervous and muscle excitation. With the difference in the concentration of ions on different sides of the membrane bind the active transfer of substances through the membrane, as well as energy conversion.

Phosphoric acid anions create a phosphate buffer system supporting the body of the intracellular medium of the body at 6.9.

Coalic acid and its anions create a bicarbonate buffer system, which maintains the pH of the extracellular medium (blood plasma) at 7.4.

Some ions are involved in the activation of enzymes, the creation of osmotic pressure in the cell, in the processes of muscle contraction, blood coagulation, etc.

Some cations and anions can be included in complexes with different substances (for example, phosphoric anions are included in phospholipids, ATP, nucleotides, etc.; FE 2+ ion is part of hemoglobin, etc.).