What is cytoplasm in biology definition - the structure of a eukaryotic cell. Structural organization of living organisms. Chemical organization of the cell

Cytology. Cytology deals with the study of cells (from the Greek cytos - cell and logos - science). The structure of cells, the structure and functions of cellular organelles, and the vital processes occurring in the cell are studied. Each cell exhibits all the properties of a living thing - metabolism, irritability, development and reproduction, and is an elementary (smallest) unit of structure. It is logical to start studying a cell by studying the chemical composition of the cell.

Chemical composition of cells.

All cells, regardless of the level of organization, are similar in chemical composition. 86 chemical elements have been discovered in living organisms periodic table D.I. Mendeleev. For 25 elements the functions they perform in the cell are known. These elements are called biogenic. Based on their quantitative content in living matter, elements are divided into three categories:

Macronutrients , elements whose concentration exceeds 0.001%. They make up the bulk of the living matter of the cell (about 99%). Macroelements are divided into elements of groups 1 and 2. Elements of the 1st group – C, N, H, O(they account for 98% of all elements). Elements of the 2nd group – K, Na, Ca, Mg, S, P, Cl, Fe (1,9%).

Microelements (Zn, Mn, Cu, Co, Mo, and many others), the share of which ranges from 0.001% to 0.000001%. Microelements are part of biologically active substances - enzymes, vitamins and hormones.

Ultramicroelements (Hg, Au, U, Ra etc.), the concentration of which does not exceed 0.000001%. The role of most elements of this group has not yet been clarified.

Macro- and microelements are present in living matter in the form of various chemical compounds, which are divided into inorganic and organic substances.

Inorganic substances include: water and minerals. Organic substances include: proteins, fats, carbohydrates, nucleic acids, ATP and other low molecular weight organic substances. The percentages are shown in Table 1.

Inorganic substances of the cell. Water.

Water is the most common inorganic compound in living organisms. Its content varies widely: in the cells of tooth enamel, water makes up about 10% by weight, and in the cells of a developing embryo – more than 90%.

Without water, life is impossible. It is not only an essential component of living cells, but also the habitat of organisms. The biological significance of water is based on its chemical and physical properties. The chemical and physical properties of water are unusual. They are explained, first of all, by the small size of water molecules, their polarity and ability to connect with each other through hydrogen bonds.

In a water molecule, one oxygen atom is covalently bonded to two hydrogen atoms. The molecule is polar: the oxygen atom carries a partial negative charge, and the two hydrogen atoms carry a partially positive charge. This makes the water molecule a dipole. Therefore, when water molecules interact with each other, hydrogen bonds are established between them. They are weaker than covalent ones, but since each water molecule is capable of forming 4 hydrogen bonds, they significantly affect the physical properties of water. The large heat capacity, heat of fusion and heat of vaporization are explained by the fact that most of the heat absorbed by water is spent on breaking hydrogen bonds between its molecules. Water has high thermal conductivity, due to which the same temperature is maintained in different parts of the cell. Water is practically incompressible and transparent in the visible part of the spectrum. Finally, water is the only substance whose density in the liquid state is greater than in the solid state.

Rice. . Water. The meaning of water.

Water – good solvent ionic (polar) compounds, as well as some non-ionic ones, the molecule of which contains charged (polar) groups. If the energy of attraction of water molecules to molecules of any substance is greater than the energy of attraction between molecules of the substance, then the molecules hydrate and the substance dissolves. In relation to water there are hydrophilic substances - substances that are highly soluble in water and hydrophobic substances - substances that are practically insoluble in water. There are organic molecules in which one section is hydrophilic and the other is hydrophobic. Such molecules are called amphipathic, these include, for example, phospholipids, which form the basis of biological membranes.

Water is a direct participant in many chemical reactions ( gyrolytic breakdown of proteins, carbohydrates, fats, etc.), necessary as metabolite for photosynthesis reactions.

Majority biochemical reactions can only be used in aqueous solution; Many substances enter and leave the cell in an aqueous solution. Due to the high heat of evaporation of water, the body cools.

The maximum density of water is at +4°C; when the temperature drops, the water rises, and since the density of ice is less than the density of water, ice forms on the surface, so when reservoirs freeze, living space remains for aquatic organisms under the ice.

Thanks to the forces cohesion(electrostatic interaction of water molecules, hydrogen bonds) and adhesion(interaction with the surrounding walls), water has the property of rising through the capillaries - one of the factors ensuring the movement of water in the vessels of plants.

The incompressibility of water determines the stressed state of cell walls ( turgor), and also performs a supporting function (hydrostatic skeleton, for example, in roundworms).

So, the importance of water for the body is as follows:

It is a habitat for many organisms;
It is the basis of the internal and intracellular environment;
Provides transport of substances;
Provides maintenance of the spatial structure of molecules dissolved in it (hydrates polar molecules, surrounds non-polar molecules, promoting their adhesion);
Serves as a solvent and medium for diffusion;
Participates in the reactions of photosynthesis and hydrolysis;
During evaporation, it participates in the thermoregulation of the body;
Provides uniform distribution of heat in the body;
The maximum density of water is at +4°C, so ice forms on the surface of the water.

Minerals.

Cell minerals are mainly represented by salts, which dissociate into anions and cations, some are used in non-ionized form (Fe, Mg, Cu, Co, Ni, etc.)

For the vital processes of the cell, the most important cations are Na +, Ca 2+, Mg 2+, and the anions HPO 4 2-, Cl -, HCO 3 -. The concentrations of ions in a cell and its habitat are usually different. In nerve and muscle cells, the concentration of K + inside the cell is 30-40 times greater than outside the cell; the concentration of Na + outside the cell is 10-12 times higher than in the cell. There are 30-50 times more Cl ions outside the cell than inside the cell. There are a number of mechanisms that allow the cell to maintain a certain ratio of ions in the protoplast and external environment.

Table 1. The most important chemical elements

Chemical element	Substances that contain a chemical element	Processes in which a chemical element is involved
Carbon, hydrogen, oxygen, nitrogen	Proteins, nucleic acids, lipids, carbohydrates and other organic substances	Synthesis of organic substances and the whole complex of functions performed by these organic substances
Potassium, sodium		Provide membrane functions, in particular, maintain the electrical potential of the cell membrane, the operation of the Na + /Ka + pump, the conduction of nerve impulses, anion, cation and osmotic balances
	Calcium phosphate, calcium carbonate Calcium pectate	Participates in the process of blood clotting, muscle contraction, is part of bone tissue, tooth enamel, and mollusk shells Formation of the median plate and cell wall in plants
	Chlorophyll	Photosynthesis
		Formation of spatial protein structure due to the formation of disulfide bridges
	Nucleic acids, ATP	Synthesis of nucleic acids, phosphorylation of proteins (their activation)
		Maintains the electrical potential of the cell membrane, the operation of the Na + /Ka + pump, the conduction of nerve impulses, anion, cation and osmotic balances Activates digestive enzymes in gastric juice
	Hemoglobin Cytochromes	Oxygen transport Electron transfer during photosynthesis and respiration
Manganese	Decarboxylases, dehydrogenases	Oxidation of fatty acids, participation in the processes of respiration and photosynthesis
	Hemocyanin Tyrosinase	Oxygen transport in some invertebrates Melanin formation
	Vitamin B 12	Formation of red blood cells
	Included in more than 100 enzymes: Alcohol dehydrogenase, carbonic anhydrase	Anaerobic respiration in plants CO 2 transport in vertebrates
	Calcium fluoride	Bone tissue, tooth enamel
	Thyroxine	Regulation of basal metabolism
Molybdenum	Nitrogenase	Nitrogen fixation

Various ions take part in many processes of cell life: cations K +, Na +, Ca 2+ provide irritability to living organisms; cations Mg 2+, Mn 2+, Zn 2+, Ca 2+, etc. are necessary for the normal functioning of many enzymes; the formation of carbohydrates during photosynthesis is impossible without Mg 2+ (a component of chlorophyll).

The concentration of salts inside the cell determines its buffer properties . Buffering is the ability of a cell to maintain the slightly alkaline reaction of its contents at a constant level (pH about 7.4). Inside the cell, buffering is provided mainly by the anions H 2 PO 4 - and HPO 4 2-. In the extracellular fluid and blood, the role of a buffer is played by H 2 CO 3 and HCO 3 -.

Phosphate buffer system:

Low pH High pH

NPO 4 2- + H + H 2 PO 4 -

Hydrogen phosphate – ion Dihydrogen phosphate – ion

Bicarbonate buffer system:

Low pH High pH

HCO 3 - + H + H 2 CO 3

Bicarbonate – ion Carbonic acid

Some inorganic substances are contained in the cell not only in a dissolved state, but also in a solid state. For example, Ca and P are contained in bone tissue and in mollusk shells in the form of double carbon dioxide and phosphate salts.

Key terms and concepts

1. General biology. 2. Tropisms, taxis, reflexes. 2. Biogenic elements. 3. Macroelements. 4. Elements of groups 1 and 2. 5. Micro- and ultramicroelements. 6. Hydrophilic and hydrophobic substances. 7. Amphipathic substances. 8. Hydrolysis. 9. Hydration. 10. Buffer.

Basic review questions

The structure of the water molecule and its properties.
The meaning of water.
The percentage of organic matter in the cell.
The most important cations of the cell and their concentration in nerve and muscle cells.
Reaction of the phosphate buffer system when pH decreases.
Reaction of the carbonate buffer system with increasing pH.

BUFFERING PROPERTIES, the ability of many substances to attenuate change active reaction(see) solution, a cut without them would have occurred when acids or alkalis were added to the solution. This stabilizing effect on the solution reaction is called a buffering effect. Buffer action. If by ten cube cm Decinormal acetic acid solution, if you gradually add a solution of caustic soda of the same concentration, then the acidity of the solution is determined by the concentration of free substances contained in it hydrogen ions(see), will decrease. At pH 1I 8 7 6 / cu. cm NaOH adding 10 cube cm NaOH, the process of binding an acid with an alkali, the neutralization process, will be completed, all the vinegar will turn into the corresponding salt, sodium acetate, and the combined H and OH ions will give water molecules. Further addition of NaOH will give predominance to free hydroxyl ions - an alkaline reaction. The curve placed here (see figure, solid line) conveys changes in the reaction expressed in terms of pH (hydrogen value, see Hydrogen ions), observed during neutralization of acetic acid. The broken line in the same figure represents the corresponding change in reaction (pH) when NaOH is added to decinormal hydrochloric acid. If you compare both curves and see how much alkali was required for the same change in the reaction, for example, to change pH from 4 to 5, then the results will turn out to be very different: in the first case, about 5 cube cm NaOH, in the second there are barely perceptible traces of the latter. The amount of alkali (or, respectively, compounds) that is required for a certain change in the reaction is a measure of the stability of the reaction of the solution and the magnitude of its B. action. In the first case it is very significant, in the second it is completely insignificant. If the number of gram equivalents of alkali (or, accordingly, acid) added to a liter of the test solution is denoted by the sign DV, and the resulting change in the reaction through DR, then, according to Van-Slyke, B. action will be equal to the ratio of these quantities: B. action = _4. c. Difference in ho- Arn de curves for both solutions discussed above is due to the properties of both compounds. Hydrochloric acid belongs to strong acids, completely dissociated into their ions. On the contrary, acetic acid is relatively weakly dissociated: only a small part of its molecules (about 1.3% in a decinormal solution) disintegrates and produces hydrogen ions, which determine the acidic reaction of the solution. Therefore, acetic acid has a significantly less acidic reaction (higher pH) than hydrochloric acid at the same molecular concentration. When NaOH is added, the hydroxyl ions of the alkali bind hydrogen ions. But due to general conditions chem. equilibrium, the removal of dissociation products causes the disintegration of new, previously undissociated molecules, releasing ever new amounts of H-ions to replace those bound by alkali. Thus, acetic acid (in contrast to completely dissociated hydrochloric acid), in addition to free, active H-ions, which determine the active reaction of the solution, also has in its undissociated molecules reserve, reserve hydrogen ions, reserve acidity, capable of quickly replenishing the loss of free ions . These acidic reserves (or alkaline, if the solution can release reserve OH ions and bind added substances) determine its B. effect; the more significant it is, the more reserve ions are mobilized for a given change in the reaction. The very name (buffer action) was given by analogy with railway buffers, softening the harshness of mechanical shocks. A more correct comparison would be with vessels of different capacities, in which the addition of the same amount of liquid causes different changes in the level. The greater the capacity of the vessel, the more liquid is required for a certain increase in the level; in the same way, the amount of alkali (or compounds) required for a given change in the “level” depends on the number of reserve H- or OH-ions (“buffer capacity”) reactions. Buffer solutions. Electrolytic dissociation of weak acids and alkalis decreases sharply in the presence of salts that have a common ion with them. For example, acetic acid is much less dissociated in the presence of its sodium salt (sodium acetate, which, like acetic acid, gives an acetate ion) and produces significantly fewer hydrogen ions than in a pure solution. The concentration of hydrogen ions is directly proportional to the concentration of acetic acid molecules and inversely proportional to the concentration of acetate ions. Since neutral salts belong to strong electrolytes, they are almost completely dissociated based on their ions, it is possible with a sufficient approximation, instead of the concentration of acetate ions, to simply take the concentration of the corresponding salt. The concentration of hydrogen ions in such a solution containing a weak acid and its salt will then be expressed by a simple formula (in which rectangular brackets indicate the concentration of the substances in them): [H"] = K [acid] [salt] (1) In the same way, in a mixture of a weak alkali and its salt, the concentration of hydroxyl ions (from which it is just as easy to calculate the closely related concentration of H-ions and the reaction of the solution) is determined by a similar expression: type that [alkali][he]=to [salt] . (2) For a more accurate calculation, it would be necessary to slightly reduce the denominator in both formulas by multiplying it by the degree of dissociation of the salt (a value less than unity). Such mixtures have especially large quantities of reserve, easily mobilized H- and OH-ions and, accordingly, a particularly large biological effect. At the same time, they make the reaction of the solution resistant to both alkalis and compounds. So, for example, a mixture of acetic acid with sodium acetate (obtained by partial neutralization of acetic acid with sodium hydroxide, see figure), as we have seen, changes its reaction relatively little when alkalized. In exactly the same way when adding strong to-you, for example, hydrochloric acid, its effect is weakened due to the fact that it combines with sodium, displacing an equivalent amount of weak acetic acid from its salt. Solutions of similar mixtures of weak acid or alkali with the corresponding salt, the so-called. buffer solutions have acquired particular importance due to the ease with which their reaction can be calculated using the given formulas (1) and (2). The constant K in these formulas represents a constant characteristic of each k-you or alkali. n. dissociation constant. If the substance and its salt are present in equal (equivalent) concentrations, then, obviously, the concentration of hydrogen ions becomes numerically equal to the dissociation constant ([H"] = K). Thus, the dissociation constant of the substance (or, accordingly , alkali) directly indicates the average reaction, in the area of the cut the effect of this mixture is manifested. At this point, the buffering effect of the b. solutions: a mixture of acetic acid and sodium acetate (acetate mixture), monometallic (primary) and dimetallic (secondary) sodium phosphate (NaH 2 P0 4 and Na 2 HP0 4) and ammonia with ammonium chloride From formulas (1) and (. 2) one very important property of buffer solutions can be directly deduced: the reaction given by the buffer mixture depends (to a first approximation) solely on the ratio Table of pH of buffer mixtures Acetic Molar ratio Acetic acid Na 32: 1 3.2 16:1 3.5 8:1 3.8 4:1 4.1 2:1 4.4 1:1 4.7 1:2 5.0 1:4 5.3 1:8 5 .6 1:16 5.9 1:32 6.2 Primary phosphate at Secondary phosphate Chlor. ammonium Ammian 1 4 7 0 3 7 3.3 8.0 8.3 8.6 8.9 9.2 9.5 9.8 10.1 10.4 10.7 11.0 its components, and not from their absolute concentration. Therefore, in the given table it was possible, without giving the concentrations of acid (or alkali) and salt, to limit ourselves to indicating their ratio. Diluting the B. solution does not affect its reaction. Of course, the same cannot be said about the buffering action. In this reaction, the higher the concentration of buffers, the more significant it is. The considered properties of B. solutions determine their most important practical applications. applications: 1. Many biochemical. and biol. processes in high degree sensitive to even minor changes in reaction (see. Active reaction And Hydrogen ions). In the very course of these processes, large quantities of acidic or alkaline products are often produced, which could change or even completely stop their further course. To accurately study such processes, it is necessary to carry them out under conditions that exclude the possibility of any significant fluctuations in the reaction. For this purpose, B. solutions are used, which are used here as reaction regulators. This method was used by Sorensen (1909) to study the effect of an active reaction on the activity of enzymes. Depending on the amount of acidic or alkaline products produced, on the one hand, and on the desired degree of constancy of the reaction, on the other, it is necessary to use solutions with b. or m. significant B. effect. 2. In other cases, the magnitude of the B action is not particularly significant, and the use of buffer solutions is based on the ability they provide to prepare stable solutions of any desired reaction (see table). With help indicators(see)-substances that change their color depending on the active reaction of the solution, you can compare the solution under study with a series of buffer solutions of a known reaction. By establishing in which of these solutions a given indicator takes on the same color as in the test one, one can determine the reaction of the latter. So. arr., buffers are used here as standard solutions, by comparison with which the reaction is measured. The use of such standard buffer solutions forms the basis of the indicator or colorimetric method for measuring reactions. Other buffer systems. Other chem. systems can also provide b. or m. significant B. action. It may depend, for example, on the precipitation of the added alkali or alkali. So, if to sea water add sodium hydroxide, the solution will become alkaline until its pH becomes approximately 8.6. During this reaction, Mg(OH) 2 will begin to precipitate, formed from magnesium salts and added NaOH; further increase in alkalinity will stop until all the magnesium has fallen out of solution. Further, even insoluble substances (for example, animal charcoal) can capture added compounds or alkalis by adsorption. Finally, proteins and other amphoteric substances have a very strong B. effect (see. Lmpholytes). Due to their dual (“amphoteric”) nature, they can bind both acids and alkalis. The amphoteric nature of cellular colloids has great importance for consistency of intracellular reaction.-Sea water buffers. Changes in reaction have a huge impact on life phenomena; life is possible only in a certain, relatively narrow, range of concentrations of H- and OH-ions for most organisms. Therefore, in nature, buffers play a large role in maintaining the constancy of the reaction necessary for life. Sea water, which represents the natural external environment of most aquatic organisms, has a very significant biological effect, which depends on the bicarbonate mixture it contains—a combination of carbon dioxide and sodium bicarbonate (sodium bicarbonate). Thanks to the presence of this buffer, the usual weakly alkaline reaction of sea water is maintained and the reaction fluctuations produced by aquatic organisms that absorb CO 2 during photosynthesis or release acidic metabolic products are moderated. Buffer properties of blood. Of particular interest are B. properties internal environment body, in particular blood. The blood has a slightly alkaline reaction, characterized by great constancy. Even in vitro, blood firmly maintains its reaction and has a very strong B. effect. It is necessary to add several tens of times more sodium hydroxide to it than to distilled water in order to cause the same alkalinization of the solution, and several hundred times more HC1 for the same acidification. Just as in sea water, the main buffer of blood serum is a bicarbonate mixture, a combination of C0 2 and NaHC0 3. The concentration of H-ions it gives is approximately determined as follows: where K equals approximately Evil -7. Whey also contains phosphates, however, compared to bicarbonates, their quantity and role are small. In terms of B. action, the bicarbonate solution is quite similar to blood serum. So, for example, both liquids dissolve the same amount of CO 2, proportional to its partial pressure in the surrounding air. When this pressure changes, as formula (3) shows, the concentration of hydrogen ions in them changes by the same amount. Whole blood with its formed elements exhibits, under the same conditions, a noticeably greater constancy of the reaction. This additional, compared to serum, B. effect depends on amphoteric protein substances in the blood, in particular, on Hb found in erythrocytes. The latter is a very weak acid, so weak that its acidic character cannot appear with an excess of CO 2. But, when the pressure of the latter is reduced, for example, in arterial blood, oxyhemoglobin, as such, decomposes a certain amount of bicarbonate, displacing CO 2 from it. As a result, the denominator in formula (3) decreases and the effect of the reduced CO 2 content is partially compensated. Thus, Hb has a significant effect on the carbon dioxide binding curve, and thereby on the blood reaction. In particular, it moderates differences associated with different CO2 pressures in arterial and venous blood. In any case, in the end, the blood reaction is completely determined by the ratio of carbon dioxide and bicarbonate, i.e., the ratio of free (dissolved) CO 2 and CO 2 chemically bound. The first is easily released from the blood, the second can be displaced by the decomposition of bicarbonates. Both of these quantities - the amount of free and bound CO 2 - jointly characterize the blood properties and reaction of the blood. Their measurement has recently become widespread and important. In terms of its reaction, blood has the same properties as other biological agents. solutions. We have seen that the reaction of a B. mixture is determined by the ratio of acid and its salt, and not by their absolute concentration. Accordingly, the blood reaction remains practically unchanged even when it is repeatedly diluted with an isotonic NaCl solution (or any other buffer-free solution). This property of blood is often used when measuring its reaction, using for this purpose a small amount of blood diluted with a NaCl solution. It also makes intravenous infusions of various so-called harmless. “saline solutions”, often having an abnormal reaction, which would be disastrous for the body if a small admixture of blood did not bring it closer to the physiological norm. When alkali is added to the blood in vitro, the latter is neutralized by carbon dioxide; on the contrary, any acid reacts with bicarbonate and, forming a neutral salt, is replaced by an equivalent amount of CO2 displaced by it from the bicarbonate. This explains a remarkable fact that has already attracted the attention of researchers more than once: by introducing various acids into the blood (in vivo), from the weakest to the strongest, it turns out to be completely impossible to achieve different (according to the strength of the drug used) changes in the blood reaction. As long as a certain amount of bicarbonate buffer remains in the blood, changes in the reaction turn out to be equally insignificant in all cases. Then, simultaneously with a sharp disruption of the reaction, death occurs. These crude experimental effects provide a clear picture of what happens in the body under natural conditions. The vast majority of metabolic products are acidic in nature (phosphoric, carbonic, lactic, butyric and other acids). Blood buffers are supposed to protect its normal reaction from these acids continuously coming from the tissues. The latter is slightly alkaline, i.e., characterized by a slight excess of active hydroxyl ions. The hydrogen index (pH) of the blood is, on average, 7.4, the concentration of H-ions is 0.44.10 -7, the concentration of OH-ions is about 7.10 _g (at 37°). Compared to this insignificant concentration of free OH ions, the number of reserve ions that can be released to bind added acids is very large (about 2.10 -2). Their number, however, is far from being as constant as the active blood reaction, and may be subject to strong changes, especially in Pat. conditions. Alkaline solutions represent only the first barrier against acidic products introduced from the outside or produced in the body. The disruption of the reaction produced by the latter is many times weakened by blood buffers, but cannot be completely eliminated by them: the binding of part of the bicarbonate molecules and the release of CO 2 shifts the initial ratio of this basic B. mixture. More subtle regulation of the reaction is carried out by the lungs. Any increase in the concentration of hydrogen ions stimulates the respiratory center and immediately increases ventilation of the lungs (see. Breath). Due to the high sensitivity of the respiratory center to H-ions, the pulmonary regulation apparatus works unusually accurately: by removing larger or smaller amounts of CO 2 from the blood, depending on the active reaction existing in it, it automatically restores the normal ratio between it and bicarbonate. Blood buffers protect the body from sharp fluctuations in the reaction, which would be disastrous for it; Breathe-helping machine ensures a constant ratio of components of the B. mixture (even when sudden changes their absolute concentration) and thereby the exact constancy of the active reaction. A particularly significant stalemate. accumulation of non-volatile acids and a corresponding decrease in reserve alkalinity are observed when acidosis(cm.). However, this usually does not lead to a change in the active blood reaction: through increased ventilation of the lungs, a decrease in CO 2 content is achieved, which in most cases compensates for the decrease in bicarbonate concentration (“compensated acidosis”). The opposite phenomenon is represented by compensated alkalosis, in which the increase in alkaline reserves is compensated by a proportional increase in CO 2 pressure. Changes in the CO 2 content in the alveolar air of the lungs can serve in both cases as a direct indicator of changes in the concentration of bicarbonates in the blood. The total amount of buffers in the blood in the first case decreases, in the second it increases, but the active reaction remains almost constant. Lit.: M i s h a e 1 i s L., Die Wassers offionen-konzentration, T. 1, Aufl. 2, B„ 1922; Kora-cuwsly W., Les ions d "hydrogene, P., 1926; Kolthoff J. M., Der Gebraueh von Farbenindi-katoren, 3 Aufl., V., 1926; Van Slyke D., The carbon dioxide carriers of the blood, Physical Review, v. I, p. 1921. D. Rubinstein. UFO, toads, tailless amphibians, fam. Bufonidae. Common species are B. vulgaris - the gray toad, or cowshed, and B. viridis - the green toad. They live in forests, bushes, gardens, cellars, old walls, under tree trunks and in other places. They are nocturnal animals. Very useful for human extermination harmful insects. The skin has saccular poisonous glands, especially powerfully developed behind the eyes (the so-called parotids); this secretion is not absorbed by human skin, which is why toads can be picked up with intact hands without any fear, but it is highly poisonous when it enters directly into the blood. The secretion of the skin glands of certain toads in tropical countries is used to make “arrow poison” (see. Amphibians, Poisonous animals).

a. Squirrels
b. mineral salts
c. carbohydrates
d. fats
2. Who owes its appearance to the harmonious system of classification of flora and fauna:
a. Jean Baptiste Lamarck
b. Carl Linnaeus
c. Charles Darwin

3. What is fertilization like in terrestrial animals:
a. External
b. Internal
c. Double

4. What intermediate products do proteins break down into in the digestive tract:
a. glycerol and fatty acids
b. simple carbohydrates
c. amino acids

5. How many chromosomes are contained in human sex gametes:
a. 23
b. 46
c. 92
6. What is the function of chloroplasts
a. Protein synthesis
b. ATP synthesis
c. Glucose synthesis
7. Cells that have a nucleus belong to:
a. Eukaryotic cell
b. Prokaryotic cell
8. Organisms that create organic matter in the ecosystem:
a. Consumers
b. Producers
c. Decomposers
9. Which cellular organelle is responsible for energy production in the cell:
a. Core
b. Chloroplast
c. Mitochondria

10. Which organelles are characteristic only of plant cells
a. Endoplasmic reticulum
b. Plastids
c. Ribosomes

11. How many chromosomes are contained in human somatic cells
a. 23
b. 46
c. 92
12. What kind of fertilization occurs in angiosperms:
a. Internal

1. List the levels of organization of life within one organism.

2. List the levels of organization of life from the organism and above.
3. Basic methods of study in biology?
4. List the elements of the first and second groups.
5. List the functions that water performs in a cell.
6. Write down an example of a buffer system.
7. What groups are carbohydrates divided into?
8. Write the formulas of the most important pentoses.
9. What substances belong to polysaccharides?
10. What is the monomer of glycogen and fiber?
11. What functions do carbohydrates perform?
12. What are fats?
13. What lipids are part of membranes?
14. List fat-soluble vitamins.
15. List 5 essential functions fat
16. Write it down general formula amino acids.
17. Write down the structural formula of the dipeptide.
18. What is the name of the bond between two amino acids?
19. What amino acids are called essential? How many are there?
20. What proteins are called complete?
21. What is the primary structure of proteins?
22. What is the secondary structure of a protein?
23. What bonds hold the tertiary structure of proteins together?
24. How much energy is released during the breakdown of 1 g of proteins, carbohydrates, lipids?
25. List the functions of proteins.
26. What are the main properties of enzymes?
27. What residues make up a DNA nucleotide?
28. Write down the structural formula of a DNA nucleotide.
29. What nitrogenous bases are part of DNA nucleotides?
30. What purine nitrogenous bases are part of the DNA molecule?
31. How are DNA nucleotides connected into one chain?
32. How many hydrogen bonds are there between complementary nitrogenous bases?
33. What is the “complementarity principle”?
34. What functions does DNA perform?
35. Write down the structural formula of the RNA nucleotide.

1) What is the long historical process of human origin called?

B1
Select Traits and Examples asexual reproduction organisms.
A) the offspring is genetically unique B) the offspring are exact copies of the parents C) the propagation of potatoes by slaughter D) the propagation of potatoes by seeds E) the offspring can develop from somatic cells E) two parents are involved in the process Adaniia B2 and write down all the letters in the required sequence in the table Establish subordination systematic categories, starting with the smallest. class Dicotyledons B) department Angiosperms C) species Dandelion officinalis D) kingdom Plants E) family Ocinaceae E) genus Dandelion

C1
How and where are the hereditary properties of organisms encoded?

Test tasks on the topic

"INORGANIC SUBSTANCES OF CELLS"

Choose one correct answer from the given options:

1. What chemical elements contained in the cell are classified as macroelements?
a) Zn, I, F, Br;

c) Ni, Cu, I, Br.

d) Au, Ag, Ra, U.

2. What are the functions of water in a cell?

c) source of energy.

d) transmission of nerve impulses

3. What ions make up hemoglobin?
a) Mg 2+;

4. The transmission of excitation through a nerve or muscle is explained by:

a) the difference in the concentrations of sodium and potassium ions inside and outside the cell

b) breaking of hydrogen bonds between water molecules

c) change in the concentration of hydrogen ions

d) thermal conductivity of water

5 . Of the following substances is hydrophilic:

a) starch

d) cellulose

6. The chlorophyll molecule contains ions

d) Na+
7. At the same time it is part of bone tissue and nucleic acids:

b) phosphorus

c) calcium

8 . Children develop rickets with a deficiency of:

a) manganese and iron

b) calcium and phosphorus

c) copper and zinc

d) sulfur and nitrogen

9 . The composition of gastric juice includes:

10. Most water is contained in cells:
a) embryo;

b) young man;

c) an old man.

d) an adult

11. What chemical elements contained in the cell are classified as microelements?
a) S, Na, Ca, K;

c) Ni, Cu, I, Br.

d) P, S, Cl, Na

12. The composition of gastric juice includes
a) sulfuric acid;

b) hydrochloric acid;

c) carbonic acid.

d) phosphoric acid

13. What are the functions minerals in a cage?
a) transfer of hereditary information;
b) environment for chemical reactions;
c) source of energy;

d) maintaining the osmotic pressure of the cell.

14. What ions affect blood clotting?
a) Mg 2+;

15 . Iron is included in:

c) hemoglobin

d) chlorophyll

16. Less water is contained in cells:
a) bone tissue;

b) nervous tissue;

V) muscle tissue.

d) adipose tissue

17. Substances that are poorly soluble in water are called:
a) hydrophilic;

b) hydrophobic;

c) amphiphilic.

d) amphoteric

18. Buffering in the cell is provided by ions:
a) Na +, K +;

b) SO 4 2-, Cl -;

c) HCO 3 -, CO 3 2-.

d) Mg 2+; Fe 2+

19. Water is the basis of life, because... she:
a) can be in three states (liquid, solid and gaseous);
b) is a solvent that ensures both the influx of substances into the cell and the removal of metabolic products from it;
c) cools the surface during evaporation.

d) has the property of thermal conductivity

20 . Of the following substances is hydrophobic:

d) potassium permanganate

Sample answers

Buffering and osmosis.
Salts in living organisms are in a dissolved state in the form of ions - positively charged cations and negatively charged anions.

The concentration of cations and anions in the cell and in its environment is not the same. The cell contains quite a lot of potassium and very little sodium. In the extracellular environment, for example, in blood plasma and sea water, on the contrary, there is a lot of sodium and little potassium. Cell irritability depends on the ratio of concentrations of Na+, K+, Ca 2+, Mg 2+ ions. The difference in ion concentrations different sides membranes ensure active transfer of substances across the membrane.

In the tissues of multicellular animals, Ca 2+ is part of the intercellular substance, which ensures the cohesion of cells and their ordered arrangement. The osmotic pressure in the cell and its buffering properties depend on the salt concentration.

Buffer is the ability of a cell to maintain the slightly alkaline reaction of its contents at a constant level.

There are two buffer systems:

1) phosphate buffer system - phosphoric acid anions maintain the pH of the intracellular environment at 6.9

2) bicarbonate buffer system - carbonic acid anions maintain the pH of the extracellular environment at a level of 7.4.

Let us consider the equations of reactions occurring in buffer solutions.

If the cell concentration increases H+ , then the hydrogen cation joins the carbonate anion:

As the concentration of hydroxide anions increases, their binding occurs:

H + OH – + H 2 O.

In this way, the carbonate anion can maintain a constant environment.

Osmotic call the phenomena occurring in a system consisting of two solutions separated by a semi-permeable membrane. IN plant cell The role of semipermeable films is performed by the boundary layers of the cytoplasm: plasmalemma and tonoplast.

Plasmalemma is the outer membrane of the cytoplasm adjacent to cell membrane. Tonoplast is the inner membrane of the cytoplasm surrounding the vacuole. Vacuoles are cavities in the cytoplasm filled with cell sap - an aqueous solution of carbohydrates, organic acids, salts, low molecular weight proteins, and pigments.

The concentration of substances in cell sap and in the external environment (soil, water bodies) are usually not the same. If the intracellular concentration of substances is higher than in the external environment, water from the environment will enter the cell, more precisely into the vacuole, at a faster rate than in the opposite direction. With an increase in the volume of cell sap, due to the entry of water into the cell, its pressure on the cytoplasm, which is tightly adjacent to the membrane, increases. When a cell is completely saturated with water, it has its maximum volume. The state of internal cell tension caused by high content water and the developing pressure of the contents of the cell on its shell is called turgor. Turgor ensures that organs maintain their shape (for example, leaves, non-lignified stems) and position in space, as well as their resistance to the action of mechanical factors. Loss of water is associated with a decrease in turgor and wilting.

If the cell is in a hypertonic solution, the concentration of which is greater than the concentration of the cell sap, then the rate of diffusion of water from the cell sap will exceed the rate of diffusion of water into the cell from the surrounding solution. Due to the release of water from the cell, the volume of cell sap is reduced and turgor decreases. A decrease in the volume of the cell vacuole is accompanied by the separation of the cytoplasm from the membrane - occurs plasmolysis.

During plasmolysis, the shape of the plasmolyzed protoplast changes. Initially, the protoplast lags behind the cell wall only in certain places, most often in the corners. Plasmolysis of this form is called angular

Then the protoplast continues to lag behind the cell walls, maintaining contact with them in certain places; the surface of the protoplast between these points has a concave shape. At this stage, plasmolysis is called concave. Gradually, the protoplast breaks away from the cell walls over the entire surface and takes on a rounded shape. This type of plasmolysis is called convex plasmolysis.

If a plasmolyzed cell is placed in a hypotonic solution, the concentration of which is less than the concentration of cell sap, water from the surrounding solution will enter the vacuole. As a result of an increase in the volume of the vacuole, the pressure of the cell sap on the cytoplasm will increase, which begins to approach the cell walls until it takes its original position - it will happen deplasmolysis

Task No. 3
After reading the given text, answer the following questions.
1) determination of buffer capacity

2) the concentration of which anions determines the buffering properties of the cell?

3) the role of buffering in the cell

4) equation of reactions occurring in a bicarbonate buffer system (on a magnetic board)

5) definition of osmosis (give examples)

6) determination of plasmolysis and deplasmolysis slides