The composition of a living cell includes the same chemical elements that are part of inanimate nature. Of the 104 elements of the periodic system of D. I. Mendeleev, 60 were found in cells.
They are divided into three groups:
- the main elements are oxygen, carbon, hydrogen and nitrogen (98% of the cell composition);
- elements that make up tenths and hundredths of a percent - potassium, phosphorus, sulfur, magnesium, iron, chlorine, calcium, sodium (1.9% in total);
- all other elements present in even smaller amounts are trace elements.
The molecular composition of the cell is complex and heterogeneous. Separate compounds - water and mineral salts - are also found in inanimate nature; others - organic compounds: carbohydrates, fats, proteins, nucleic acids, etc. - are characteristic only of living organisms.
INORGANIC SUBSTANCES
Water makes up about 80% of the mass of the cell; in young fast-growing cells - up to 95%, in old ones - 60%.
The role of water in the cell is great.
It is the main medium and solvent, participates in most chemical reactions, the movement of substances, thermoregulation, the formation of cellular structures, determines the volume and elasticity of the cell. Most substances enter the body and are excreted from it in an aqueous solution. The biological role of water is determined by the specificity of the structure: the polarity of its molecules and the ability to form hydrogen bonds, due to which complexes of several water molecules arise. If the attraction energy between water molecules is less than between water molecules and a substance, it dissolves in water. Such substances are called hydrophilic (from the Greek "hydro" - water, "fillet" - I love). These are many mineral salts, proteins, carbohydrates, etc. If the energy of attraction between water molecules is greater than the energy of attraction between molecules of water and a substance, such substances are insoluble (or slightly soluble), they are called hydrophobic (from the Greek "phobos" - fear) - fats, lipids, etc.
Mineral salts in aqueous solutions of the cell dissociate into cations and anions, providing a stable amount of the necessary chemical elements and osmotic pressure. Of the cations, the most important are K + , Na + , Ca 2+ , Mg + . The concentration of individual cations in the cell and in the extracellular environment is not the same. In a living cell, the concentration of K is high, Na + is low, and in blood plasma, on the contrary, there is a high concentration of Na + and low K +. This is due to the selective permeability of membranes. The difference in the concentration of ions in the cell and the environment ensures the flow of water from the environment into the cell and the absorption of water by the roots of plants. The lack of individual elements - Fe, P, Mg, Co, Zn - blocks the formation of nucleic acids, hemoglobin, proteins and other vital substances and leads to serious diseases. Anions determine the constancy of the pH-cell environment (neutral and slightly alkaline). Of the anions, the most important are HPO 4 2-, H 2 PO 4 -, Cl -, HCO 3 -
ORGANIC SUBSTANCES
Organic substances in the complex form about 20-30% of the cell composition.
Carbohydrates- organic compounds consisting of carbon, hydrogen and oxygen. They are divided into simple - monosaccharides (from the Greek "monos" - one) and complex - polysaccharides (from the Greek "poly" - a lot).
Monosaccharides(their general formula is C n H 2n O n) - colorless substances with a pleasant sweet taste, highly soluble in water. They differ in the number of carbon atoms. Of the monosaccharides, hexoses (with 6 C atoms) are the most common: glucose, fructose (found in fruits, honey, blood) and galactose (found in milk). Of the pentoses (with 5 C atoms), the most common are ribose and deoxyribose, which are part of nucleic acids and ATP.
Polysaccharides refers to polymers - compounds in which the same monomer is repeated many times. The monomers of polysaccharides are monosaccharides. Polysaccharides are water soluble and many have a sweet taste. Of these, the most simple disaccharides, consisting of two monosaccharides. For example, sucrose is made up of glucose and fructose; milk sugar - from glucose and galactose. With an increase in the number of monomers, the solubility of polysaccharides decreases. Of the high molecular weight polysaccharides, glycogen is the most common in animals, and starch and fiber (cellulose) in plants. The latter consists of 150-200 glucose molecules.
Carbohydrates- the main source of energy for all forms of cellular activity (movement, biosynthesis, secretion, etc.). Splitting to the simplest products CO 2 and H 2 O, 1 g of carbohydrate releases 17.6 kJ of energy. Carbohydrates perform a building function in plants (their shells consist of cellulose) and the role of reserve substances (in plants - starch, in animals - glycogen).
Lipids- These are water-insoluble fat-like substances and fats, consisting of glycerol and high molecular weight fatty acids. Animal fats are found in milk, meat, subcutaneous tissue. At room temperature, they are solids. In plants, fats are found in seeds, fruits, and other organs. At room temperature, they are liquids. Fat-like substances are similar to fats in chemical structure. There are many of them in the yolk of eggs, brain cells and other tissues.
The role of lipids is determined by their structural function. They make up cell membranes, which, due to their hydrophobicity, prevent the contents of the cell from mixing with the environment. Lipids perform an energy function. Splitting to CO 2 and H 2 O, 1 g of fat releases 38.9 kJ of energy. They poorly conduct heat, accumulating in the subcutaneous tissue (and other organs and tissues), perform a protective function and the role of reserve substances.
Squirrels- the most specific and important for the body. They belong to non-periodic polymers. Unlike other polymers, their molecules consist of similar but non-identical monomers - 20 different amino acids.
Each amino acid has its own name, special structure and properties. Their general formula can be represented as follows
An amino acid molecule consists of a specific part (radical R) and a part that is the same for all amino acids, including an amino group (-NH 2) with basic properties, and a carboxyl group (COOH) with acidic properties. The presence of acidic and basic groups in one molecule determines their high reactivity. Through these groups, the connection of amino acids occurs in the formation of a polymer - protein. In this case, a water molecule is released from the amino group of one amino acid and the carboxyl of another, and the released electrons are combined to form a peptide bond. Therefore, proteins are called polypeptides.
A protein molecule is a chain of several tens or hundreds of amino acids.
Protein molecules are huge, so they are called macromolecules. Proteins, like amino acids, are highly reactive and are able to react with acids and alkalis. They differ in composition, quantity and sequence of amino acids (the number of such combinations of 20 amino acids is almost infinite). This explains the diversity of proteins.
There are four levels of organization in the structure of protein molecules (59)
- Primary Structure- a polypeptide chain of amino acids linked in a certain sequence by covalent (strong) peptide bonds.
- secondary structure- a polypeptide chain twisted into a tight helix. In it, low-strength hydrogen bonds arise between the peptide bonds of adjacent turns (and other atoms). Together, they provide a fairly strong structure.
- Tertiary structure is a bizarre, but specific configuration for each protein - a globule. It is held together by weak hydrophobic bonds or cohesive forces between non-polar radicals that are found in many amino acids. Due to their multiplicity, they provide sufficient stability of the protein macromolecule and its mobility. The tertiary structure of proteins is also supported by covalent S - S (es - es) bonds that arise between radicals of the sulfur-containing amino acid cysteine, which are distant from each other.
- Quaternary structure not typical for all proteins. It occurs when several protein macromolecules combine to form complexes. For example, human blood hemoglobin is a complex of four macromolecules of this protein.
This complexity of the structure of protein molecules is associated with a variety of functions inherent in these biopolymers. However, the structure of protein molecules depends on the properties of the environment.
Violation of the natural structure of the protein is called denaturation. It can occur under the influence of high temperature, chemicals, radiant energy and other factors. With a weak impact, only the quaternary structure breaks down, with a stronger one, the tertiary one, and then the secondary one, and the protein remains in the form of a primary structure - the polypeptide chain. This process is partially reversible, and the denatured protein is able to restore its structure.
The role of protein in cell life is enormous.
Squirrels is the building material of the body. They are involved in the construction of the shell, organelles and membranes of the cell and individual tissues (hair, blood vessels, etc.). Many proteins act as catalysts in the cell - enzymes that speed up cellular reactions by tens, hundreds of millions of times. About a thousand enzymes are known. In addition to protein, their composition includes metals Mg, Fe, Mn, vitamins, etc.
Each reaction is catalyzed by its own particular enzyme. In this case, not the entire enzyme acts, but a certain area - the active center. It fits to the substrate like a key to a lock. Enzymes act at a certain temperature and pH. Special contractile proteins provide motor functions of cells (movement of flagellates, ciliates, muscle contraction, etc.). Individual proteins (blood hemoglobin) perform a transport function, delivering oxygen to all organs and tissues of the body. Specific proteins - antibodies - perform a protective function, neutralizing foreign substances. Some proteins perform an energy function. Breaking down to amino acids, and then to even simpler substances, 1 g of protein releases 17.6 kJ of energy.
Nucleic acids(from the Latin "nucleus" - the core) were first discovered in the core. They are of two types - deoxyribonucleic acids(DNA) and ribonucleic acids(RNA). Their biological role is great, they determine the synthesis of proteins and the transfer of hereditary information from one generation to another.
The DNA molecule has a complex structure. It consists of two spirally twisted chains. The width of the double helix is 2 nm 1 , the length is several tens and even hundreds of micromicrons (hundreds or thousands of times larger than the largest protein molecule). DNA is a polymer whose monomers are nucleotides - compounds consisting of a molecule of phosphoric acid, a carbohydrate - deoxyribose and a nitrogenous base. Their general formula is as follows:
Phosphoric acid and carbohydrate are the same for all nucleotides, and there are four types of nitrogenous bases: adenine, guanine, cytosine, and thymine. They determine the name of the corresponding nucleotides:
- adenyl (A),
- guanyl (G),
- cytosyl (C),
- thymidyl (T).
Each DNA strand is a polynucleotide consisting of several tens of thousands of nucleotides. In it, neighboring nucleotides are connected by a strong covalent bond between phosphoric acid and deoxyribose.
With the enormous size of DNA molecules, the combination of four nucleotides in them can be infinitely large.
During the formation of the DNA double helix, the nitrogenous bases of one strand are arranged in a strictly defined order against the nitrogenous bases of the other. At the same time, T is always against A, and only C is against G. This is explained by the fact that A and T, as well as G and C, strictly correspond to each other, like two halves of broken glass, and are additional or complementary(from the Greek "complement" - addition) to each other. If the sequence of nucleotides in one DNA strand is known, then the nucleotides of another strand can be established by the principle of complementarity (see Appendix, task 1). Complementary nucleotides are joined by hydrogen bonds.
Between A and T there are two bonds, between G and C - three.
The duplication of the DNA molecule is its unique feature, which ensures the transfer of hereditary information from the mother cell to the daughter cells. The process of DNA duplication is called DNA replication. It is carried out as follows. Shortly before cell division, the DNA molecule unwinds and its double chain is split into two independent chains by the action of an enzyme from one end. On each half of the free nucleotides of the cell, according to the principle of complementarity, a second chain is built. As a result, instead of one DNA molecule, two completely identical molecules appear.
RNA- a polymer similar in structure to one strand of DNA, but much smaller. RNA monomers are nucleotides consisting of phosphoric acid, a carbohydrate (ribose) and a nitrogenous base. The three nitrogenous bases of RNA - adenine, guanine and cytosine - correspond to those of DNA, and the fourth is different. Instead of thymine, RNA contains uracil. The formation of the RNA polymer occurs through covalent bonds between the ribose and phosphoric acid of neighboring nucleotides. Three types of RNA are known: messenger RNA(i-RNA) transmits information about the structure of the protein from the DNA molecule; transfer RNA(t-RNA) transports amino acids to the site of protein synthesis; ribosomal RNA (rRNA) is found in ribosomes and is involved in protein synthesis.
ATP- adenosine triphosphoric acid is an important organic compound. Structurally, it is a nucleotide. It consists of the nitrogenous base adenine, carbohydrate - ribose and three molecules of phosphoric acid. ATP is an unstable structure, under the influence of the enzyme, the bond between "P" and "O" is broken, a molecule of phosphoric acid is split off and ATP passes into
As we already know, the cell is made up of organic and inorganic chemicals. The main inorganic substances that make up the cell are salts and water.
Water as a component of life
Water is the dominant component of all organisms. Important biological functions of water are carried out due to the unique properties of its molecules, in particular the presence of dipoles, which make it possible to form hydrogen bonds between cells.
Thanks to water molecules in the body of living beings, the processes of thermal stabilization and thermoregulation occur. The process of thermoregulation occurs due to the high heat capacity of water molecules: external temperature changes do not affect temperature changes inside the body.
Thanks to water, the organs of the human body retain their elasticity. Water is one of the main components of the lubricating fluids necessary for the joints of vertebrates or the pericardial sac.
It is included in the mucus, which facilitates the movement of substances through the intestines. Water is a component of bile, tears and saliva.
Salts and other inorganic substances
The cells of a living organism, in addition to water, contain such inorganic substances as acids, bases and salts. Mg2+, H2PO4, K, CA2, Na, C1- are the most important in the life of the organism. Weak acids guarantee a stable internal cell environment (slightly alkaline).
The concentration of ions in the intercellular substance and inside the cell can be different. So, for example, Na + ions are concentrated only in the intercellular fluid, while K + is found exclusively in the cell.
A sharp reduction or increase in the number of certain ions in the composition of the cell not only leads to its dysfunction, but also to death. For example, a decrease in the amount of Ca + in the cell causes convulsions inside the cell and its further death.
Some inorganic substances often interact with fats, proteins and carbohydrates. So a striking example are organic compounds with phosphorus and sulfur.
Sulfur, which is part of protein molecules, is responsible for the formation of molecular bonds in the body. Thanks to the synthesis of phosphorus and organic substances, energy is released from protein molecules.
Calcium salts
Calcium salts contribute to the normal development of bone tissue, as well as the functioning of the brain and spinal cord. The exchange of calcium in the body is carried out due to vitamin D. An excess or lack of calcium salts leads to dysfunction of the body.
The chemical composition of plant and animal cells is very similar, which indicates the unity of their origin. More than 80 chemical elements have been found in cells.
The chemical elements present in the cell are divided into 3 large groups: macronutrients, mesoelements, microelements.
Macronutrients include carbon, oxygen, hydrogen and nitrogen. Mesoelements are sulfur, phosphorus, potassium, calcium, iron. Trace elements - zinc, iodine, copper, manganese and others.
Biologically important chemical elements of the cell:
Nitrogen - structural component of proteins and NA.
Hydrogen- is a part of water and all biological compounds.
Magnesium- activates the work of many enzymes; structural component of chlorophyll.
Calcium- the main component of bones and teeth.
Iron- enters into hemoglobin.
Iodine- part of the thyroid hormone.
Substances of the cell are divided into organic(proteins, nucleic acids, lipids, carbohydrates, ATP) and inorganic(water and mineral salts).
Water makes up to 80% of the mass of the cell, plays important role:
water in the cell is a solvent
· transports nutrients;
With water, harmful substances are removed from the body;
high heat capacity of water;
Evaporation of water helps to cool animals and plants.
Gives elasticity to the cell.
Minerals:
participate in maintaining homeostasis by regulating the flow of water into the cell;
Potassium and sodium ensure the transport of substances across the membrane and are involved in the occurrence and conduction of a nerve impulse.
Mineral salts, primarily calcium phosphates and carbonates, give hardness to bone tissue.
Solve a problem on the genetics of human blood
Proteins, their role in the body
Protein- organic substances found in all cells, which consist of monomers.
Protein- high molecular weight non-periodic polymer.
Monomer is an amino acid (20).
Amino acids contain an amino group, a carboxyl group and a radical. Amino acids are linked together to form a peptide bond. Proteins are extremely diverse, for example, there are over 10 million of them in the human body.
The diversity of proteins depends on:
1. different AK sequence
2. by size
3. from composition
Protein structures
The primary structure of a protein - a sequence of amino acids connected by a peptide bond (linear structure).
The secondary structure of a protein - spiral structure.
Tertiary structure of a protein- globule (glomerular structure).
Quaternary protein structure- consists of several globules. Characteristic of hemoglobin and chlorophyll.
Protein properties
1. Complementarity: the ability of a protein to fit in shape to some other substance like a key to a lock.
2. Denaturation: violation of the natural structure of the protein (temperature, acidity, salinity, addition of other substances, etc.). Examples of denaturation: a change in protein properties when eggs are boiled, the transition of protein from a liquid to a solid state.
3. Renaturation - restoration of the protein structure, if the primary structure has not been disturbed.
Protein functions
1. Building: the formation of all cell membranes
2. Catalytic: proteins are catalysts; speed up chemical reactions
3. Motor: actin and myosin are part of muscle fibers.
4. Transport: transfer of substances to various tissues and organs of the body (hemoglobin is a protein that is part of red blood cells)
5. Protective: antibodies, fibrinogen, thrombin - proteins involved in the development of immunity and blood coagulation;
6. Energy: participate in plastic exchange reactions to build new proteins.
7. Regulatory: the role of the hormone insulin in the regulation of blood sugar.
8. Storage: the accumulation of proteins in the body as reserve nutrients, for example, in eggs, milk, plant seeds.
A cell is not only a structural unit of all living things, a kind of brick of life, but also a small biochemical factory in which various transformations and reactions take place every fraction of a second. This is how the structural components necessary for the life and growth of the organism are formed: the mineral substances of the cell, water and organic compounds. Therefore, it is very important to know what will happen if one of them is not enough. What role do various compounds play in the life of these tiny, structural particles of living systems that are not visible to the naked eye? Let's try to understand this issue.
Classification of cell substances
All compounds that make up the mass of the cell, form its structural parts and are responsible for its development, nutrition, respiration, plastic and normal development, can be divided into three large groups. These are categories such as:
- organic;
- cells (mineral salts);
- water.
Often the latter is referred to the second group of inorganic components. In addition to these categories, you can designate those that are made up of their combination. These are metals that make up the molecule of organic compounds (for example, a hemoglobin molecule containing an iron ion is protein in nature).
Minerals of the cell
If we talk specifically about the mineral or inorganic compounds that make up each living organism, then they are also not the same both in nature and in quantitative content. Therefore, they have their own classification.
All inorganic compounds can be divided into three groups.
- Macronutrients. Those whose content inside the cell is more than 0.02% of the total mass of inorganic substances. Examples: carbon, oxygen, hydrogen, nitrogen, magnesium, calcium, potassium, chlorine, sulfur, phosphorus, sodium.
- Trace elements - less than 0.02%. These include: zinc, copper, chromium, selenium, cobalt, manganese, fluorine, nickel, vanadium, iodine, germanium.
- Ultramicroelements - the content is less than 0.0000001%. Examples: gold, cesium, platinum, silver, mercury and some others.
You can also highlight several elements that are organogenic, that is, they form the basis of organic compounds from which the body of a living organism is built. These are elements such as:
- hydrogen;
- nitrogen;
- carbon;
- oxygen.
They build the molecules of proteins (the basis of life), carbohydrates, lipids and other substances. However, minerals are also responsible for the normal functioning of the body. The chemical composition of the cell is calculated in dozens of elements from the periodic table, which are the key to successful life. Only about 12 of all atoms do not play a role at all, or it is negligible and not studied.
Some salts are especially important, which must be ingested with food every day in sufficient quantities so that various diseases do not develop. For plants, this is, for example, sodium. For humans and animals, these are calcium salts, table salt as a source of sodium and chlorine, etc.
Water
The mineral substances of the cell are combined with water into a common group, therefore, it is impossible not to say about its significance. What role does it play in the body of living beings? Huge. At the beginning of the article, we compared the cell to a biochemical factory. So, all the transformations of substances that occur every second are carried out precisely in the aquatic environment. It is a universal solvent and medium for chemical interactions, synthesis and decay processes.
In addition, water is part of the internal environment:
- cytoplasm;
- cell sap in plants;
- blood in animals and humans;
- urine;
- saliva of other biological fluids.
Dehydration means death for all organisms without exception. Water is the living environment for a huge variety of flora and fauna. Therefore, it is difficult to overestimate the importance of this inorganic substance, it is truly infinitely great.
Macronutrients and their meaning
Mineral substances of a cell for its normal work are of great importance. First of all, this applies to macronutrients. The role of each of them has been studied in detail and has long been established. We have already listed which atoms make up the group of macroelements, so we will not repeat ourselves. Let us briefly outline the role of the main ones.
- Calcium. Its salts are necessary for the supply of Ca 2+ ions to the body. The ions themselves are involved in the processes of blood arrest and clotting, provide cell exocytosis, as well as muscle contractions, including cardiac contractions. Insoluble salts are the basis of strong bones and teeth of animals and humans.
- Potassium and sodium. Maintain the state of the cell, form the sodium-potassium pump of the heart.
- Chlorine - is involved in ensuring the electroneutrality of the cell.
- Phosphorus, sulfur, nitrogen - are components of many organic compounds, and also take part in the work of muscles, the composition of bones.
Of course, if we consider each element in more detail, then much can be said about its excess in the body, and about its deficiency. After all, both are harmful and lead to diseases of various kinds.
trace elements
The role of minerals in the cell, which belong to the group of microelements, is also great. Despite the fact that their content is very small in the cell, without them it will not be able to function normally for a long time. The most important of all the above atoms in this category are such as:
- zinc;
- copper;
- selenium;
- fluorine;
- cobalt.
A normal level of iodine is essential for maintaining thyroid function and hormone production. Fluorine is needed by the body to strengthen tooth enamel, and plants - to maintain elasticity and rich color of the leaves.
Zinc and copper are elements that make up many enzymes and vitamins. They are important participants in the processes of synthesis and plastic exchange.
Selenium is an active participant in the processes of regulation; it is an element necessary for the functioning of the endocrine system. Cobalt, on the other hand, has another name - vitamin B 12, and all compounds of this group are extremely important for the immune system.
Therefore, the functions of mineral substances in the cell, which are formed by microelements, are no less than those that are performed by macrostructures. Therefore, it is important to consume both of them in sufficient quantities.
Ultramicroelements
The mineral substances of the cell, which are formed by ultramicroelements, do not play such a significant role as those mentioned above. However, their long-term deficiency can lead to the development of very unpleasant, and sometimes very dangerous consequences for health.
For example, selenium is also included in this group. Its long-term deficiency provokes the development of cancerous tumors. Therefore, it is considered indispensable. But gold and silver are metals that have a negative effect on bacteria, destroying them. Therefore, inside the cells play a bactericidal role.
However, in general, it should be said that the functions of ultramicroelements have not yet been fully disclosed by scientists, and their significance remains unclear.
Metals and organic substances
Many metals are part of organic molecules. For example, magnesium is a coenzyme of chlorophyll, necessary for plant photosynthesis. Iron is part of the hemoglobin molecule, without which it is impossible to breathe. Copper, zinc, manganese and others are parts of the molecules of enzymes, vitamins and hormones.
Obviously, all these compounds are important for the body. It is impossible to attribute them completely to mineral ones, but it still follows in part.
Mineral substances of the cell and their meaning: grade 5, table
To summarize what we said during the article, we will compile a general table in which we will reflect what mineral compounds are and why they are needed. You can use it when explaining this topic to schoolchildren, for example, in the fifth grade.
Thus, the mineral substances of the cell and their significance will be learned by schoolchildren in the course of the main stage of education.
Consequences of a lack of mineral compounds
When we say that the role of minerals in the cell is important, we must give examples that prove this fact.
We list some diseases that develop with a lack or excess of any of the compounds indicated in the course of the article.
- Hypertension.
- Ischemia, heart failure.
- Goiter and other diseases of the thyroid gland (Basedow's disease and others).
- Anemia.
- Wrong growth and development.
- Cancer tumors.
- Fluorosis and caries.
- Blood diseases.
- Disorder of the muscular and nervous system.
- Indigestion.
Of course, this is not a complete list. Therefore, it is necessary to carefully monitor that the daily diet is correct and balanced.
Lesson #2
Lesson topic : Inorganic substances of the cell.
The purpose of the lesson: to deepen knowledge about the inorganic substances of the cell.
Lesson objectives:
Educational: Consider the structural features of water molecules in connection with its most important role in the life of the cell, reveal the role of water and mineral salts in the life of living organisms;
Developing: Continue the development of students' logical thinking, continue the formation of skills to work with various sources of information;
Educational: To continue the formation of a scientific worldview, the education of a biologically literate personality; the formation and development of the moral and ideological foundations of the individual; to continue the formation of ecological consciousness, education of love for nature;
Equipment : multimedia application for the textbook, projector, computer, task cards,scheme "Elements. Substances of the cell". Test tubes, beaker, ice, spirit lamp, table salt, ethyl alcohol, sucrose, vegetable oil.
Basic concepts: dipole, hydrophilicity, hydrophobicity, cations, anions.
Lesson type : combined
Teaching methods : reproductive, partially exploratory, experimental.
Learners must:
Know the main chemical elements and compounds that make up the cell;
Be able to explain the importance of inorganic substances in life processes.
Lesson structure
1. Organizational moment
Greetings, preparation for work.
There is a mental warm-up at the beginning and at the end of the lesson. Its purpose is to determine the emotional state of students. Each student is given a plate with six faces - a scale for determining the emotional state (Fig. 1). Each student puts a tick under the face, whose expression reflects his mood.
2. Checking students' knowledge
Test "Chemical composition of the cell" (Appendix)
3. Goal setting and motivation
"Water! You have no taste, no color, no smell, you cannot be described. A person enjoys you, not understanding what you really are. You cannot say that you are necessary for life, you are life itself. You give everywhere and everywhere a feeling of bliss that cannot be understood by any of our senses. You give us strength back. Your mercy revives the dried-up fountains of our hearts. You are the greatest wealth in the world. You are a wealth that can be easily frightened away, but you give us such a simple and precious happiness, ”this enthusiastic hymn to water was written by the French writer and pilot Antoine de Saint-Exupery, who had to experience the pangs of thirst in a hot desert.
With these wonderful words, we begin the lesson, the purpose of which is to expand the understanding of water - the substance that created our planet.
- Update
What is the importance of water in human life?
(Student answers about the importance of water in human life0
- Presentation of new material.
Water is the most common inorganic substance in living organisms, its essential component, habitat for many organisms, and the main solvent of the cell.
Lines of M. Dudnik's poem:
They say that eighty percent of the water is man,
From the water, I will add, his native rivers,
From the water, I will add, the rains that they gave him to drink,
From the water, I will add, from the ancient water of the springs,
From which grandfathers and great-grandfathers drank.
Examples of water content in various cells of the body:
In a young human or animal body - 80% of the cell mass;
In the cells of the old organism - 60%
In the brain - 85%;
In the cells of tooth enamel - 10-15%.
With the loss of 20% of water, a person dies.
Consider the structure of a water molecule:
H2O - molecular formula,
Н–О–Н – structural formula,
The water molecule has an angular structure: it is an isosceles triangle with an apex angle of 104.5°.
The molecular weight of water in the vapor state is 18 g/mol. However, the molecular weight of liquid water is higher. This indicates that in liquid water there is an association of molecules caused by hydrogen bonds.
What is the role of water in a cell?
Due to the high polarity of the molecules, water is the solvent of other polar compounds without equal. More substances dissolve in water than in any other liquid. That is why many chemical reactions take place in the aquatic environment of the cell. Water dissolves metabolic products and removes them from the cell and the body as a whole.
Water has a high heat capacity, i.e. ability to absorb heat. With a minimal change in its own temperature, a significant amount of heat is released or absorbed. Due to this, it protects the cell from sudden changes in temperature. Since a lot of heat is spent on the evaporation of water, by evaporating water, organisms can protect themselves from overheating (for example, during sweating).
Water has a high thermal conductivity. This property creates the ability to evenly distribute heat between the tissues of the body.
Water is one of the main substances of nature, without which the development of the organic world of plants, animals, and humans is impossible. Where it is, there is life.
Demonstration of experiences. Make a spreadsheet with students.
a) Dissolve the following substances in water: table salt, ethyl alcohol, sucrose, vegetable oil.
Why do some substances dissolve in water and others do not?
The concept of hydrophilic and hydrophobic substances is given.
Hydrophilic substances are substances that are highly soluble in water.
Hydrophobic substances are substances that are poorly soluble in water.
b) Drop a piece of ice into a glass of water.
What can you say about the density of water and ice?
Using the textbook in groups, you need to fill out the table "Mineral salts". At the end of the work there is a discussion of the data entered in the table.
Buffering - the ability of a cell to maintain the relative constancy of a weakly alkaline environment.
- Consolidation of the studied material.
Solving biological problems in groups.
Task 1.
In some diseases, a 0.85% solution of table salt, called saline, is injected into the blood. Calculate: a) how many grams of water and salt you need to take to get 5 kg of saline; b) how many grams of salt is introduced into the body when 400 g of saline is infused.
Task 2.
In medical practice, a 0.5% solution of potassium permanganate is used to wash wounds and gargle. What volume of a saturated solution (containing 6.4 g of this salt in 100 g of water) and pure water must be taken to prepare 1 liter of a 0.5% solution (ρ = 1 g/cm 3 ).
Exercise.
Write cinquain topic: water
- Homework: item 2.3
Find in literary works examples of describing the properties and qualities of water, its biological significance.
Scheme "Elements. Substances of the cell"
Reference outline for the lesson
