Chemical composition of cells
Macroelements, their role in the cell. About 70 elements of D.I. Mendeleev’s periodic system of elements were found in the cells of different organisms, but only 24 of them have a well-established significance and are constantly found in all types of cells.
The largest share in the elemental composition of the cell is made up of oxygen, carbon, hydrogen and nitrogen. These are the so-called basic, or biogenic, elements. The atoms of these elements form the molecules of all organic substances in cells; they account for more than 95% of the mass of cells, and the relative content of elements in living matter is much higher than in the earth’s crust. To the main elements organic molecules also include phosphorus and sulfur.
In addition, calcium, magnesium, potassium, sodium and chlorine (in animal cells), which are included in the cell in the form of ions, are vitally important. Their content in the cell is calculated in tenths and hundredths of a percent. The listed elements make up a group of macroelements.
Calcium ions take part in the regulation of a number of cellular processes, including muscle contraction and other motor functions, as well as in blood coagulation. Insoluble calcium salts are involved in the formation of bones and teeth, calcium carbonate is involved in the formation of mollusk shells and strengthening the cell membranes of some plant species. The concentration of magnesium ions is important for maintaining the integrity and function of ribosomes. In addition, magnesium is part of chlorophyll and supports the normal functioning of mitochondria.
Potassium and sodium ions are involved in maintaining a certain ionic strength and creating a buffer environment, regulate osmotic pressure in the cell, determine the normal rhythm of cardiac activity, ensure the transmission nerve impulse. Chlorine in the form of anions participates in the creation of the salt environment of animal organisms (for plants, chlorine is a trace element) and, in addition, is sometimes included in organic compounds.
Microelements, their role in the cell. Other chemical elements - copper, manganese, iron, cobalt, zinc, and also (for some organisms) boron, fluorine, chromium, selenium, aluminum, silicon, molybdenum and iodine - are contained in small quantities(no more than 0.01% of cell mass). They belong to the group of microelements.
The percentage content of a particular element in the body in no way characterizes the degree of its importance and necessity in the body. Cobalt, for example, is part of vitamin B12, iodine is part of the hormones thyroxine and thyronine, and copper is part of enzymes that catalyze redox processes; in addition, copper is involved in the transport of oxygen in the tissues of mollusks. Iron is an integral part of complexes that perform a number of vital functions important functions. These include, for example, hemoglobin heme, some enzymes and electron carriers (cytochrome C).
A significant number of enzymes with a diverse mechanism of action contain ions of zinc, manganese, cobalt and molybdenum.
Silicon is found in diatoms, horsetails, sponges and mollusks. In the cartilages and ligaments of vertebrates, its content can reach several hundredths of a percent.
Boron affects plant growth, fluorine is part of the enamel of teeth and bones.
1. Give definitions of concepts.
Element- a collection of atoms with equal charge nucleus and the number of protons coinciding with the serial (atomic) number in the periodic table.
Microelement
- an element that is found in very low concentrations in the body.
Macronutrient
- an element that is found in high concentrations in the body.
Bioelement- a chemical element involved in the life of a cell and forms the basis of biomolecules.
Elemental composition of the cell
- percentage of chemical elements in the cell.
2. What is one of the proofs of the community of living and inanimate nature?
Unity chemical composition. There are no elements characteristic only of inanimate nature.
3. Fill out the table.
ELEMENTAL COMPOSITION OF A CELL
4. Give examples organic matter, whose molecules consist of three, four and five macroelements.
3 elements: carbohydrates and lipids.
4 elements: proteins.
5 elements: nucleic acids, proteins.
5. Fill out the table.
BIOLOGICAL ROLE OF ELEMENTS
6. Study the section “Role” in § 2.2 external factors in the formation of the chemical composition of living nature” and answer the question: “What are biochemical endemics, and what are the reasons for their origin?”
Biochemical endemics are diseases of plants, animals and humans caused by a sharp deficiency or excess of any element in a certain area.
7. What diseases do you know associated with a lack of microelements?
Iodine deficiency - endemic goiter. A decrease in the synthesis of thyroxine and the resulting proliferation of thyroid tissue.
Lack of iron – iron deficiency anemia.
8. Remember on what basis chemical elements are divided into macro-, micro- and ultra-microelements. Propose your own alternative classification of chemical elements (for example, by functions in a living cell).
Micro-, macro- and ultra-microelements are divided based on their percentage in the cell. In addition, it is possible to classify elements by function that regulate the activity of certain organ systems: nervous, muscular, circulatory and cardiovascular, digestive, etc.
9. Choose the correct answer.
Test 1.
What chemical elements form most organic substances?
2) C, O, H, N;
Test 2.
Does not apply to macroelements:
4) manganese.
Test 3.
Living organisms need nitrogen because it serves:
1) integral component proteins and nucleic acids;
10. Determine the characteristic by which all of the following elements, except one, are combined into one group. Emphasize this “extra” element.
Oxygen, hydrogen, sulfur, iron, carbon, phosphorus, nitrogen. Contains only DNA. And the rest are all in proteins.
11. Explain the origin and general meaning words (terms), based on the meaning of the roots that make up them.
12. Choose a term and explain how it is modern meaning corresponds to the original meaning of its roots.
Selected term– organogen.
Correspondence: the term, in principle, corresponds to its original meaning, but today there is more precise definition. Previously, the meaning was such that the elements took part only in the construction of tissues and organ cells. Now it is clear that biologically important elements not only form chemical molecules in cells, etc., but also regulate all processes in cells, tissues and organs. They are part of hormones, vitamins, enzymes and other biomolecules.
13. Formulate and write down the main ideas of § 2.2.
The elemental composition of a cell is the percentage of chemical elements in the cell. Cell elements are usually classified, depending on their percentage, into micro-, macro- and ultramicroelements. Those elements that participate in the life of the cell, form the basis of biomolecules, are called bioelements.
Macroelements include: C N H O. They are the main components of all organic compounds in a cage. In addition, P S K Ca Na Fe Cl Mg - are part of all the most important biomolecules. Without them, the body cannot function. Their deficiency leads to death.
For microelements: Al Cu Mn Zn Mo Co Ni I Se Br F B, etc. They are also necessary for the normal functioning of the body, but not so critical. Their deficiency causes disease. They are part of the biological active compounds, affect metabolism.
There are ultramicroelements: Au Ag Be, etc. Physiological role has not been definitively established. But they are important for the cell.
There is the concept of “biochemical endemics” - diseases of plants, animals and humans caused by a sharp deficiency or excess of any element in a certain area. For example, endemic goiter (iodine deficiency).
If there is a deficiency of an element due to diet, illness or illness may also occur. For example, with a lack of iron - anemia. With a lack of calcium - frequent fractures, hair loss, teeth loss, muscle pain.
The biological role of chemical elements in the human body is extremely diverse.
The main function of macroelements is to build tissues, maintain constant osmotic pressure, ionic and acid-base composition.
Microelements, being part of enzymes, hormones, vitamins, biologically active substances as complexing agents or activators, they participate in metabolism, reproduction processes, tissue respiration, and neutralization of toxic substances. Microelements actively influence the processes of hematopoiesis, oxidation - reduction, permeability of blood vessels and tissues. Macro- and microelements - calcium, phosphorus, fluorine, iodine, aluminum, silicon - determine the formation of bone and dental tissues.
There is evidence that the content of some elements in the human body changes with age. Thus, the content of cadmium in the kidneys and molybdenum in the liver increases with old age. The maximum zinc content is observed during puberty, then it decreases and reaches a minimum in old age. The content of other microelements, such as vanadium and chromium, also decreases with age.
Many diseases associated with a deficiency or excessive accumulation of various microelements have been identified. Fluoride deficiency causes dental caries, iodine deficiency causes endemic goiter, and excess molybdenum causes endemic gout. These kinds of patterns are associated with the fact that the human body maintains a balance of optimal concentrations of biogenic elements - chemical homeostasis. Violation of this balance is followed by
A deficiency or excess of an element can lead to various diseases
In addition to the six main macroelements - organogens - carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus, which make up carbohydrates, fats, proteins and nucleic acids, “inorganic” macroelements are necessary for normal nutrition of humans and animals - calcium, chlorine, magnesium, potassium , sodium - and trace elements - copper, fluorine, iodine, iron, molybdenum, zinc, and also, possibly (proven for animals), selenium, arsenic, chromium, nickel, silicon, tin, vanadium.
A lack of elements such as iron, copper, fluorine, zinc, iodine, calcium, phosphorus, magnesium and some others in the diet leads to serious consequences for human health.
However, it must be remembered that not only a deficiency, but also an excess is harmful to the body. nutrients, since this disrupts chemical homeostasis. For example, when excess manganese is consumed with food, the level of copper in the plasma increases (synergism of Mn and Cu), and in the kidneys it decreases (antagonism). An increase in molybdenum content in foods leads to an increase in the amount of copper in the liver. Excess zinc in food causes inhibition of the activity of iron-containing enzymes (2n and Fe antagonism).
Mineral components, which are vital in negligible quantities, become toxic at higher concentrations.
The vital necessity, deficiency, toxicity of a chemical element are presented in the form of a dependence curve “Concentration of the element in food products- body reaction” (Fig. 5.5). The approximately horizontal section of the curve (plateau) describes the area of concentrations corresponding to optimal growth, health, and reproduction. The large extent of the plateau indicates not only the low toxicity of the element, but also the greater ability of the organism to adapt to significant changes in the content of this element. On the contrary, a narrow plateau indicates significant toxicity of the element and a sharp transition from quantities necessary for the body to life-threatening ones. When you go beyond a plateau (increasing microelement concentration), all elements become toxic. Ultimately, a significant increase in the concentration of trace elements can lead to death.
A number of elements (silver, mercury, lead, cadmium, etc.) are counted
They are toxic, since their entry into the body even in microquantities leads to severe pathological phenomena. Chemical mechanism The toxic effects of some trace elements will be discussed below.
Biogenic elements are widely used in agriculture. Adding small amounts of microelements to the soil - boron, copper, manganese, zinc, cobalt, molybdenum - dramatically increases the yield of many crops. It turns out that microelements, by increasing the activity of enzymes in plants, promote the synthesis of proteins, vitamins, nucleic acids, sugars and starch. Some of the chemical elements have a positive effect on photosynthesis, accelerate the growth and development of plants, and seed ripening. Microelements are added to animal feed to increase their productivity.
Widely used various elements and their compounds as medicines.
Thus, studying the biological role of chemical elements, elucidating the relationship between the metabolism of these elements and other biologically active substances - enzymes, hormones, vitamins - contributes to the creation of new drugs and the development of optimal dosage regimens for both therapeutic and prophylactic purposes.
IN modern conditions One of the most pressing problems in teaching chemistry is ensuring the practical orientation of subject knowledge. This means the need to clarify the close relationship between the theoretical principles being studied and the practice of life, demonstrating the applied nature chemical knowledge. Students begin to study chemistry with interest. In order to maintain the cognitive interest of students, it is necessary to convince them of the effectiveness of chemical knowledge and to form a personal need to master the educational material.
Target this lesson: broaden students' horizons and increase cognitive interest in studying the subject, form ideological concepts about the knowability of nature. This lesson is proposed to be taught in 8th grade after studying the chemical elements of the Periodic Table, when the children already have an idea of their diversity.
PROGRESS OF THE LESSON
Teacher:
There is nothing else in nature
Neither here nor there, in the depths of space:
Everything – from small grains of sand to planets –
It consists of uniform elements.
Like the formula, like work schedule,
The structure of the Mendeleev system is strict.
What's happening around you the world is alive,
Enter it, inhale it, touch it with your hands.
The lesson begins with a theatrical skit “Who is most important in the table?” (cm. Appendix 1).
Teacher: The human body contains 81 chemical elements out of 92 found in nature. The human body is complex chemical laboratory. It is difficult to imagine that our daily well-being, mood and even appetite can depend on minerals. Without them, vitamins are useless, the synthesis and breakdown of proteins, fats and carbohydrates is impossible.
On the students’ desks are tables “Biological role of chemical elements” (see. Appendix 2). Time is given to get to know her. The teacher and students analyze the table by asking questions.
Teacher: The basis of life is made up of six elements of the first three periods (H, C, N, O, P, S), which account for 98% of the mass of living matter (the remaining elements of the periodic table account for no more than 2%).
Three main characteristics of nutrients (H, C, N, O, P, S):
- small atomic size,
- small relative atomic mass,
- the ability to form strong covalent bonds.
Students are given texts (see Appendix 3). Assignment: read the text carefully; identify elements necessary for life and elements dangerous to living organisms; find them in the Periodic Table and explain their role.
After completing the assignment, several students analyze different texts.
Teacher: Analogue elements in the natural environment enter into competition and can be interchanged in living organisms, negatively affecting them.
Replacing sodium and potassium in animals and humans with lithium causes disorders of the nervous system, since in this case the cells do not conduct nerve impulses. Similar violations lead to schizophrenia.
Thallium, a biological competitor of potassium, replaces it in cell walls and affects the central and peripheral nervous system, gastrointestinal tract and kidneys.
Selenium can replace sulfur in proteins. This is the only element that, when present in high levels in plants, can cause sudden death in animals and humans who eat them.
When calcium is deficient in the soil, the body replaces it with strontium, which gradually disrupts the normal structure of the skeleton. Particularly dangerous is the replacement of calcium with strontium-90, which accumulates in huge quantities at sites of nuclear explosions (during nuclear weapons testing) or during accidents at nuclear power plants. This radionuclide destroys bone marrow.
Cadmium competes with zinc. This element reduces the activity of digestive enzymes, disrupts the formation of glycogen in the liver, causes skeletal deformation, inhibits bone growth, and also causes severe pain in the lower back and leg muscles, and brittle bones (for example, broken ribs when coughing). Other negative consequences are lung and rectal cancer, pancreatic dysfunction. Kidney damage, decreased levels of iron, calcium, and phosphorus in the blood. This element inhibits self-purification processes in aquatic and terrestrial plants (for example, a 20-30-fold increase in cadmium in tobacco leaves is noted).
Halogens can be very easily interchanged in the body. Excess fluorine in the environment (fluoridated water, soil contamination with fluorine compounds around an aluminum production plant and other reasons) prevents the entry of iodine into the human body. In this regard, diseases of the thyroid gland occur, endocrine system generally.
Student messages prepared in advance.
1st student:
Medieval alchemists considered gold to be perfection, and other metals to be an error in the act of creation, and, as is known, they made great efforts to eliminate this error. The idea of introducing gold into medical practice is attributed to Paracelsus, who declared that the goal of chemistry should not be the transformation of all metals into gold, but the preparation of medicines. Medicines made from gold and its compounds have been tried to treat many diseases. They were used to treat leprosy, lupus, and tuberculosis. In people sensitive to gold, it could cause a disturbance in the blood composition, a reaction in the kidneys, liver, affect mood, teeth and hair growth. Gold ensures the functioning of the nervous system. It is found in corn. And the strength of blood vessels depends on germanium. The only food product containing germanium is garlic.
2nd student:
IN human body the largest amount of copper is found in the brain and liver, and this circumstance alone indicates its importance in life. It has been found that during pain, the concentration of copper in the blood and cerebrospinal fluid increases. In Syria and Egypt, newborns are given copper bracelets to prevent rickets and epilepsy.
3rd student:
ALUMINUM
Aluminum cookware is called the poor man's cookware, as this metal contributes to the development of senile atherosclerosis. When cooking food in such containers, aluminum partially passes into the body, where it accumulates.
4th student:
- What element is contained in apples? (Iron.)
- What is it biological role? (The body contains 3 g of iron, of which 2 g is in the blood. Iron is part of hemoglobin. Insufficient iron content leads to headache, rapid fatigue.)
Then students conduct a laboratory experiment, the purpose of which is to experimentally prove the effect of salts of certain metals on protein. They mix the protein with solutions of alkali and copper sulfate and observe the formation of a purple precipitate. They conclude that the protein is destroyed.
5th student:
Man is also nature.
He is also a sunset and a sunrise.
And there are four seasons in it.
And there is a special way of music in it.
And the special mystery of color,
Sometimes with cruel, sometimes with kind fire.
The man is winter. Or summer.
Or autumn. With thunder and rain.It contained everything – miles and time.
And he became blind from atomic storms.
Man is both soil and seed.
And a weed in the middle of the field. And bread.And what is the weather like there?
How much loneliness is there in him? Meetings?
Man is also nature...
So let's save nature!
(S. Ostrovoy)
To consolidate the knowledge acquired in the lesson, the “Smile” test is carried out (see. Appendix 4).
Next, you are asked to fill out the crossword puzzle “Chemical Kaleidoscope” (see. Appendix 5).
The teacher sums up the lesson, noting the most active students.
6th student:
Change, change!
The call is ringing.
It's finally finished
Annoying lesson!Pulling sulfur by the pigtail,
Magnesium ran past.
The iodine from the class has evaporated,
It was as if I had never been there at all.Fluoride accidentally set the water on fire
Chlorine ate someone else's book.
Carbon suddenly with hydrogen
Managed to become invisible.Potassium and bromine are fighting in the corner:
They won't share the electron.
Oxygen is a naughty boy in the woods
He galloped past on horseback.
Literature used:
- O.V. Baidalina On the applied aspect of chemical knowledge. “Chemistry at school” No. 5, 2005
- Chemistry and ecology in school course. “First of September” No. 14, 2005
- I. N. Pimenov, A. V. Pimenov“Lectures on general biology”, training manual, Saratov, OJSC Publishing House “Lyceum”, 2003
- About chemistry in verse, Who is most important in the table? “First of September”, No. 15, 2005
- Metals in the human body. “Chemistry at school”, No. 6, 2005.
- Crossword “Chemical Kaleidoscope”. “First of September”, No. 1 4, 2005
- “I'm going to chemistry class.” Book for teachers. M. “First of September”, 2002, p. 12.
