Water. Of the inorganic substances that make up the cell, the most important is water. Its amount ranges from 60 to 95% total mass cells. Water plays a vital role in the life of cells and living organisms in general. In addition to the fact that it is part of their composition, for many organisms it is also a habitat.
The role of water in a cell is determined by its unique chemical and physical properties, associated mainly with the small size of its molecules, the polarity of its molecules and their ability to form hydrogen bonds with each other.
And it was believed that Earth's primitive atmosphere had a very similar chemical composition. After several months of work, reactions between all compounds produced a large number of organic molecules, including amino acids, that were found in solution in water.
Thus was born the first coherent theory of the origin of life: prebiotic monomers were synthesized in the primitive atmosphere of the Earth, fell into the sea, were absorbed by clays, polymerized and became primitive cells. This scenario was quickly questioned, at least with respect to amino acid synthesis.
Water as a component biological systems performs the following essential functions:
Water is a universal solvent for polar substances, such as salts, sugars, alcohols, acids, etc. Substances that are highly soluble in water are called hydrophilic. When a substance goes into solution, its molecules or ions are able to move more freely; Accordingly, the reactivity of the substance increases. Exactly because of this reason most of chemical reactions in the cell occur in aqueous solutions. Its 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, a source of hydrogen ions and free oxygen.
First of all, it could never contain much hydrogen, which is too light for the gas to be held by Earth's gravity. Even if the Earth had an abundance of these compounds in the beginning, they would quickly disappear, or at least become a very minority.
The earth was born from the collection of dust and meteorites that fell on each other. Dust and meteorites contain 25% iron, 79% silicates, 0.9% water and 0.1% organic matter and other gases. When these dust and meteorites collected, it caused a lot of heat, and the Earth in the molten layer of Iron descended to the center and formed the core, the silicates were located above and formed the mantle and crust. Water, gas and carbon compounds were concentrated on the surface to give an atmosphere and Since the carbon of meteorites is reduced carbon, one would expect this primitive atmosphere to be itself rich in reduced carbon.
Water does not dissolve non-polar substances and does not mix with them, since it cannot form hydrogen bonds with them. Substances that are insoluble in water are called hydrophobic. Hydrophobic molecules or parts of them are repelled by water, and in its presence they are attracted to each other. Such interactions play important role in ensuring the stability of membranes, as well as many protein molecules, nucleic acids and a number of subcellular structures.
But this is not to mention very high temperature, which prevailed during the formation of the Earth. The organic matter of dust and meteorites contains carbon. However, since the invention of iron metallurgy, the following is known chemical reaction: reduced iron carbon oxide → reduced iron carbon dioxide. This is what happens in blast furnaces with carbon reduction of iron ores. In the formative Earth, even hotter than a blast furnace, organic matter must be oxidized by iron oxides, and become carbon dioxide.
Water has a high specific heat capacity. Breaking the hydrogen bonds that hold water molecules together requires the absorption of a large amount of energy. This property ensures the maintenance heat balance body with significant temperature changes in environment. In addition, water has high thermal conductivity, which allows the body to maintain same temperature in its entirety.
So Miller's experience and those who followed him are very interesting, but they don't touch the Earth. Moreover, this reaction was an old industrial technology used to produce molecular hydrogen. But in such modern conditions this organo-synthesis does not occur because the atmosphere and sea contain molecular oxygen, which prevents such organo-synthesis.
When we talk about the possible oceanic origin of prebiotic molecules, we often confuse this with current ecosystems that are the hydrothermal vents of the world's oceans and their smokers. This chemical energy is the basis of the complex ecosystems of today's oceanic hydrothermal vents.
Water is characterized by a high heat of vaporization, i.e., the ability of molecules to carry with them significant amount heat while cooling the body. Thanks to this property of water, which manifests itself during sweating in mammals, thermal shortness of breath in crocodiles and other animals, and transpiration in plants, overheating is prevented.
Molecular clouds and nebulae
It is possible that mineral organosynthesis occurs in these current devices, but the molecules that can be produced are quite marginal to those produced by the chemosynthesis of living organisms, so the ecosystems of current oceanic hydrothermal vents are in no way equivalent to very old hydrothermal ecosystems . Spectral studies have even recently identified glycine, the simplest of amino acids.
It has been shown that these small molecules must interact with each other on the surface of the dust and ice grains present in these nebulae. Fortunately, we have access to "witnesses" of little or no altered dust and objects present in our nebulae, amounting to 4.5 hectares: these are comets, witnesses of what happened in the outer solar system, and chondrites, witnesses of what happened in the inner solar system.
Water is characterized by exceptionally high surface tension. This property is very important for adsorption processes, for the movement of solutions through tissues (blood circulation, ascending and descending currents in plants). For many small organisms, surface tension allows them to float on water or glide across its surface.
The degassing of comets as they pass near the Sun releases many radicals and organic molecules, a list of which is given in the following figure. The analysis technique did not allow us to determine the molecular structure of these compounds, simply to recognize them atomic composition. These molecules, which were in the form of solid grains, were necessarily macromolecules, and not small organic molecules, which would be gaseous in the interplanetary void.
As for meteorites, they are much easier to analyze directly since laboratories have kilograms of them. Among all these meteorites, some of them are called "carbonaceous chondrites" because they contain 0.1 to 5% organic matter. What do these carbon meteorites contain? Much of this organic matter in meteorites consists of very large insoluble molecules, the structure of which should resemble that shown in the following figure.
Water ensures the movement of substances in the cell and body, the absorption of substances and the removal of metabolic products.
In plants, water determines the turgor of cells, and in some animals it performs supporting functions, being a hydrostatic skeleton (round and annelids, echinoderms).
Water - component lubricating fluids (synovial - in the joints of vertebrates, pleural - in pleural cavity, pericardial - in the pericardial sac) and mucus (facilitate the movement of substances through the intestines, create a moist environment on the mucous membranes respiratory tract). It is part of saliva, bile, tears, sperm, etc.
A small percentage of this organic matter consists of smaller molecules that are soluble in water or various solvents, and among these molecules are precisely amino acids and nitrogenous bases. The following figure gives the list and proportions of these soluble organic molecules.
What is the origin of this organic matter from comets and meteorites? Some probably came from molecules present in the presolar nebula, but most were probably synthesized in the early solar system because the young sun emitted a lot ionizing radiation. The action of these radiations on trace gas molecules, especially those trapped on the surface of grains of dust and ice, would produce these complex organic molecules.
Mineral salts. Inorganic substances in the cage, in addition to water, prespavlevye mineral salts. Salt molecules in an aqueous solution break down into cations and anions. Highest value have cations (K+, Na+, Ca2+, Mg:+, NH4+) and anions (C1, H2P04 -, HP042-, HC03 -, NO32--, SO4 2-) Not only the content, but also the ratio of ions in the cell is significant .
Arrival of meteorites and comet dust
This average meteorite sees its surface heat up through the atmosphere due to friction. This friction and this heating evaporate the surface to a thickness of several cm, and the meteorite often breaks, but for a meteorite of this size, only its periphery will evaporate. This heart will have no time to heat, it will remain cold and land on the ground. If we see this fall, we will see what is called a race car, and we will raise a "beautiful" meteorite.
If the meteorite was small, it would be completely vaporized by the heat generated by atmospheric friction before reaching this equilibrium speed. We will witness the fall of a falling star, but nothing will happen to the earth. Now imagine a large meteorite 10 times larger. In fact, the volume changes like a cube of rays, and the surface changes like a square of rays. The kinetic energy of his meteorite falling into top part atmosphere is proportional to its mass. The surface of our large meteorite will become very hot, but it will not be able to evacuate all of its energy and will not evaporate more than a tiny part of the meteorite; the deceleration will be very slight.
The difference between the amounts of cations and anions on the surface and inside the cell ensures the occurrence of an action potential, which underlies the occurrence of nervous and muscle excitation. The difference in ion concentrations on different sides of the membrane determines the active transfer of substances across the membrane, as well as energy conversion.
And then all its kinetic energy is instantly converted into heat and excess pressure; our meteorite will be completely evaporated. Each surface unit would have to evacuate 10 4 times less energy than the average meteorite, which it could easily bypass, even without heating. Our micrometeorite will slow down without heating, and the fourth case concerns micrometeorites, but also comet tails from comet tails, such micrometeorites or dust are collected by the stratospheric aircraft or melting cubic meters Antarctic ice. ultra-clean.
Phosphoric acid anions create a phosphate buffer system that maintains the pH of the body's intracellular environment at 6.9.
Carbonic acid and its anions form a bicarbonate buffer system that maintains the pH of the extracellular environment (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 clotting, etc.
From the four cases we have considered, we see that Case 2 and Case 3 lead to complete destruction evaporation of a meteorite if it contains organic matter in the form of amino acid monomers. or nitrogenous bases, they are completely destroyed. On the other hand, we see that in case No. 1 and case No. 4 the meteorite is not destroyed or heated. If it contains organic matter in the form of amino acids such as monomers or nitrogen bases, it will remain intact in the soil.
We know the mass of meteorites of all sizes that are currently falling to Earth, especially in the form of micrometeorites. Extrapolating this amount to early days Earth, when the bombardment was much more intense, it was discovered that the amount of organic matter that arrived on Earth without destruction in these distant times must have been much greater than the mass of all living things. current.
A number of cations and anions are necessary for the synthesis of important organic substances (for example, phospholipids, ATP, nucleotides, hemoglobin, hemocyanin, chlorophyll, etc.), as well as amino acids, being sources of nitrogen and sulfur atoms.
Source: N.A. Lemeza L.V. Kamlyuk N.D. Lisov "Biology manual for applicants to higher education institutions"
Substances accumulate in the cells of the embryo and, more often, in its cotyledons, the first embryonic leaves. The embryo is a miniature plant with vegetative organs: an embryonic shoot (embryo-stem, cotyledons, embryonic bud) and an embryonic root. Storage substances in endosperm cells (storage tissue) or in cotyledon cells are represented by fats, proteins, carbohydrates, organic acids, ...
This step in the synthesis of monomers such as nitrogenous bases and amino acids does not present a problem. If the primitive earth's atmosphere probably did not allow such syntheses, contrary to what was believed 50 years ago, two other sources besides the incompatible ones existed or were possible: space and the ocean. Could the molecules at the heart of life come from the ocean, space, or both? Could we, molecularly speaking, be of extraterrestrial or oceanic origin?
Therefore, the source of life is a problem that has not yet been solved, but we are beginning to look at the mechanisms that have moved from mineral matter to the first cells, “spontaneous paleogeneration.” Many stages remain unclear, in particular the passage of macromolecules to the first cells.
At least 40 kJ/mol of energy is expended, which is accumulated in macroergic bonds: Consequently, the main importance of the processes of respiration and photosynthesis is determined by the fact that they supply energy for the synthesis of ATP, with the participation of which most of the work is performed in the cell. Thus, ATP is the main universal supplier of energy in the cells of all living organisms. ATP is extremely...
But for what precedes this fateful moment representing the passage of molecules into life, geology and astronomy bring a lot. The answers will be provided to chemists and biologists. . If these ideas are correct, then the emergence of life should be relatively spontaneous and mild phenomenon as soon as conditions permit. This is what the rate at which life appeared on Earth suggests: less than 200 million years.
This text was commissioned by the General Council of Allaire as part of the preparatory work for the European Center of Paleontology, which will be built in Gannat in the coming years. The name tissue salt is derived from the concept of the twelve basic mineral salts, found in tissues and cells of the human body. Essentially, they are compounds of sodium, potassium, iron, calcium, sulfur, phosphorus, chlorine and silicon, which are a natural component human body. Their balance and proper movement are essential to maintaining health.
With oxygen, restoration - deprivation of oxygen. With the introduction of electronic concepts into chemistry, the concept of redox reactions was extended to reactions in which oxygen does not participate. In inorganic chemistry, redox reactions (ORRs) can be formally considered as the movement of electrons from an atom of one reagent (reductant) to an atom of another (...
His theory is based on three main ideas. The basic unit of life is the cell. The essence of the disease is a pathologically altered cell. Human health is determined sufficient quantity essential minerals V correct ratio. The correct concentration of 12 essential mineral salts in the bioplasma ensures natural balance and restoration of the body. If they are insufficient, the biochemical balance in the body is disrupted. Symptoms of the disease appear as a result of a deficiency of certain minerals in the body.
Inorganic components cannot be produced by the body, so they must be obtained from food. Today's Agriculture gives us food that is often depleted of minerals. In this form, inorganic substances are better absorbed into cells and tissues, and the cells are also provided with information to restore their ability to obtain minerals from food.
Biology [ Complete guide for preparation for the Unified State Exam] Lerner Georgy Isaakovich
2.3.1. Inorganic substances of the cell
The cell contains about 70 elements periodic table Mendeleev's elements, and 24 of them are present in all types of cells. All elements present in the cell are divided, depending on their content in the cell, into groups:
macronutrients– H, O, N, C,. Mg, Na, Ca, Fe, K, P, Cl, S;
microelements– B, Ni, Cu, Co, Zn, Mb, etc.;
ultramicroelements– U, Ra, Au, Pb, Hg, Se, etc.
Molecules that make up a cell inorganic And organic connections.
Inorganic compounds of the cell - water And inorganic ions.
Water is the most important inorganic substance of the cell. All biochemical reactions occur in aqueous solutions. The water molecule has a nonlinear spatial structure and has polarity. Hydrogen bonds are formed between individual water molecules, which determine the physical and Chemical properties water.
Physical properties of water: Since water molecules are polar, water has the property of dissolving polar molecules of other substances. Substances that are soluble in water are called hydrophilic. Substances that are insoluble in water are called hydrophobic.
Water has a high specific heat capacity. To break the numerous hydrogen bonds present between water molecules, a large amount of energy must be absorbed. Remember how long it takes for a kettle to heat up to boiling. This property of water ensures the maintenance of thermal balance in the body.
To evaporate water, quite a lot of energy is required. The boiling point of water is higher than that of many other substances. This property of water protects the body from overheating.
Water can be in three states of aggregation - liquid, solid and gaseous.
Hydrogen bonds determine the viscosity of water and the adhesion of its molecules to molecules of other substances. Thanks to the adhesive forces of molecules, a film is created on the surface of water with the following characteristics: surface tension.
When cooled, the movement of water molecules slows down. The number of hydrogen bonds between molecules becomes maximum. Water reaches its greatest density at 4 C?. When water freezes, it expands (needing space for hydrogen bonds to form) and its density decreases. That's why ice floats.
Biological functions water. Water ensures the movement of substances in the cell and body, the absorption of substances and the removal of metabolic products. In nature, water carries waste products into soils and water bodies.
Water is an active participant in metabolic reactions.
Water is involved in the formation of lubricating fluids and mucus, secretions and juices in the body. These fluids are found in the joints of vertebrates, in the pleural cavity, and in the pericardial sac.
Water is part of mucus, which facilitates the movement of substances through the intestines and creates a moist environment on the mucous membranes of the respiratory tract. The secretions secreted by some glands and organs are also water-based: saliva, tears, bile, sperm, etc.
Inorganic ions. Inorganic ions of the cell include: cations K +, Na +, Ca 2+, Mg 2+, NH 3 + and anions Cl –, NO 3 -, H 2 PO 4 -, NCO 3 -, HPO 4 2-.
The difference between the number of cations and anions (Nа + , Ka + , Cl -) on the surface and inside the cell ensures the occurrence of an action potential, which underlies nervous and muscle excitation.
Anions phosphorus acids create phosphate buffer system, maintaining the pH of the intracellular environment of the body at a level of 6-9.
Carbonic acid and its anions create a bicarbonate buffer system and maintain the pH of the extracellular environment (blood plasma) at a level of 7-4.
Nitrogen compounds serve as a source of mineral nutrition, synthesis of proteins and nucleic acids. Phosphorus atoms are part of nucleic acids, phospholipids, as well as the bones of vertebrates and the chitinous cover of arthropods. Calcium ions are part of the substance of bones; they are also necessary for muscle contraction and blood clotting.
EXAMPLES OF TASKS
A1. The polarity of water determines its ability
1) conduct heat 3) dissolve sodium chloride
2) absorb heat 4) dissolve glycerin
A2. Children with rickets should be given medications containing
1) iron 2) potassium 3) calcium 4) zinc
A3. The conduction of a nerve impulse is provided by ions:
1) potassium and sodium 3) iron and copper
2) phosphorus and nitrogen 4) oxygen and chlorine
A4. Weak bonds between water molecules in its liquid phase are called:
1) covalent 3) hydrogen
2) hydrophobic 4) hydrophilic
A5. Hemoglobin contains
1) phosphorus 2) iron 3) sulfur 4) magnesium
A6. Select group chemical elements, which is necessarily part of proteins
A7. For patients with hypofunction thyroid gland give medications containing
Part B
IN 1. Select the functions of water in the cage
1) energy 4) construction
2) enzymatic 5) lubricating
3) transport 6) thermoregulatory
AT 2. Select only physical properties water
1) ability to dissociate
2) hydrolysis of salts
3) density
4) thermal conductivity
5) electrical conductivity
6) electron donation
Part WITH
C1. What physical properties of water determine it biological significance?
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