G.N. PETRAKOVICH. Another aspect of the topic. Our eyes, if not a mirror of the soul, then their transparent media - the pupil and the iris - are still screens for the topographic "movie" constantly coming from us. "Whole" holograms fly through the pupils, and in the irises, protons carrying a significant charge of kinetic energy continuously excite the molecules in the pigment clumps. They will excite them until everything is in order in the cells that "sent" their protons to these molecules. Cells will die, something else will happen to them, to the organ - the structure in lumps of pigments will immediately change. This will be clearly recorded by experienced iridologists: they already know for sure - from the projections in the iris - which organ is sick and even with what. Early and accurate diagnosis! Some physicians are not very favorable to their colleagues-iridodiagnostics, considering them almost charlatans. In vain! Iridology, as simple, accessible, cheap, easily translated into mathematical language, and most importantly - accurate and early method diagnosis of various diseases in the near future shines " green light". The only drawback of the method was the lack of a theoretical base. Its foundation is set out above. CORRESPONDENT. I think it would be necessary for our readers to explain the process of formation of holograms of each individual. You will do it better than me. G.N. PETRAKOVICH. Let us imagine interactions of accelerated protons with some large bulk (three-dimensional) molecule in a cell, occurring very quickly. For such interactions with the nuclei of the target atoms that make up this large molecule, many protons will be consumed, which, in turn, will leave, in turn, a volumetric, but "negative" trace in the form of vacuum, "holes" in the proton beam, too. This trace will be the real hologram, which embodies and retains a part of the structure of the molecule itself that reacted with protons. A series of holograms (which happens "in nature") will display and preserve not only the physical "appearance" of the molecule, but also the order of physical and chemical transformations of its individual parts and the entire molecule as a whole over a certain period of time. Such holograms, merging into larger volumetric images, can display life cycle the whole cell, many neighboring cells, organs and parts of the body - the whole body. There is another consequence. Here it is. In wildlife, regardless of consciousness, we communicate primarily with fields. In such communication, having entered into resonance with other fields, we risk losing, partially or completely, our individual frequency (as well as purity), and if in communication with green nature this means "dissolve in nature", then in communication with people, especially with those who have a strong field, it means to partially or completely lose their individuality - to become a "zombie" (according to Todor Dichev). There are no technical devices for "zombie" under the program and it is unlikely that they will ever be created, but the impact of one person on another in this regard is quite possible, although, from the standpoint of morality, it is unacceptable. In self-care, this should be considered, especially when it comes to noisy collective actions, in which it is not reason and not even true feeling that always prevails, but fanaticism - the sad child of malicious resonance. The flow of protons can only increase due to merging with other flows, but in no way, in contrast to, for example, an electron flow, not mix - and then it can carry complete information already about whole organs and tissues, including - and about such a specific organ like the brain. Apparently, we think in programs, and these holograms are able to transmit a stream of protons through our eyes - this is evidenced not only by the "expressiveness" of our eyes, but also by the fact that animals are able to assimilate our holograms. In confirmation of this, one can refer to the experiments of the famous trainer V.L. Durov, in which Academician V.M. Bekhterev. In these experiments, a special commission immediately came up with any tasks that were feasible for them, V.L. Durov immediately handed over these tasks to the dogs with a "hypnotic look" (at the same time, as he said, he himself, as it were, became a "dog" and mentally completed the tasks with them), and the dogs exactly fulfilled all the instructions of the commission. By the way, photography of hallucinations can also be associated with holographic thinking and the transmission of images by a stream of protons through the gaze. Highly important point: information-carrying protons "mark" the protein molecules of their body with their energy, while each "labeled" molecule acquires its own spectrum, and with this spectrum it differs from a molecule exactly the same in chemical composition, but belonging to a "foreign" body. The principle of mismatch (or coincidence) in the spectrum of protein molecules underlies immune reactions organism, inflammation, as well as tissue incompatibility, as we have already mentioned. The olfaction mechanism is also built on the principle of spectral analysis of molecules excited by protons. But in this case, all molecules of the substance in the air inhaled through the nose are irradiated with protons with an instant analysis of their spectrum (the mechanism is very close to the mechanism of color perception). But there is a "work" that is performed only by a high-frequency alternating electromagnetic field - this is the work of the "second", or "peripheral" heart, about which a lot was written at one time, but whose mechanism no one has yet discovered. This is a special topic for conversation. To be continued... The vital activity of cells requires energy costs. Living systems (organisms) receive it from external sources, for example, from the Sun (phototrophs, which are plants, some types of protozoa and microorganisms), or produce it themselves (aerobic autotrophs) as a result of the oxidation of various substances (substrates).
In both cases, cells synthesize a universal high-energy ATP molecule (adenosine triphosphoric acid), the destruction of which releases energy. This energy is expended to perform all types of functions - active transport of substances, synthetic processes, mechanical work, etc.
The ATP molecule itself is quite simple and is a nucleotide consisting of adenine, ribose sugar and three phosphoric acid residues (Fig.). The molecular weight of ATP is small and is 500 daltons. ATP is the universal carrier and store of energy in the cell, which is contained in high-energy bonds between three phosphoric acid residues.
structural formula spatial formula
Figure 37. Adenosine triphosphoric acid (ATP)
Molecule Colors( spatial formula): white - hydrogen, red - oxygen, green - carbon, blue - nitrogen, dark red - phosphorus
The splitting of only one phosphoric acid residue from an ATP molecule is accompanied by the release of a significant portion of energy - about 7.3 kcal.
How does the process of storing energy in the form of ATP take place? Consider this on the example of the oxidation (combustion) of glucose - a common source of energy for converting the chemical bonds of ATP into energy.
Figure 38. Structural formula
glucose (content in human blood - 100 mg%)
The oxidation of one mole of glucose (180 g) is accompanied by
is produced by the release of about 690 kcal of free energy.
C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + E (about 690 kcal)
In a living cell, this huge amount of energy is not released immediately, but gradually in the form of a stepwise process and is regulated by a number of oxidative enzymes. At the same time, the released energy is not converted into thermal energy, as during combustion, but is stored in the form of chemical bonds in the ATP molecule (macroergic bonds) in the process of ATP synthesis from ADP and inorganic phosphate. This process can be compared to the operation of a battery, which is charged from various generators and can provide energy to many machines and devices. In the cell, the role of a unified battery is performed by the system of adenosine-di and tri-phosphoric acids. Charging the adenyl battery consists in the combination of ADP with inorganic phosphate (phosphorylation reaction) and the formation of ATP:
ADP + F inorg ATP + H 2 O
For the formation of only 1 ATP molecule, energy is required from the outside in the amount of 7.3 kcal. Conversely, when ATP is hydrolyzed (battery discharged), the same amount of energy is released. Payment for this energy equivalent, called in bioenergetics “quantum of biological energy”, comes from external resources - that is, at the expense of nutrients. The role of ATP in the life of a cell can be represented as follows:
Energy System System Functions
re-accumulation of used cells
energy resources
Fig.39 Overall plan cell energy
The synthesis of ATP molecules occurs not only due to the breakdown of carbohydrates (glucose), but also proteins (amino acids) and fats (fatty acids). The general scheme of cascades of biochemical reactions is as follows (Fig.).
1. The initial stages of oxidation occur in the cytoplasm of cells and do not require the participation of oxygen. This form of oxidation is called anaerobic oxidation, or more simply - glycolysis. The main substrate for anaerobic oxidation is hexoses, mainly glucose. In the process of glycolysis, incomplete oxidation of the substrate occurs: glucose breaks down to triose (two molecules of pyruvic acid). At the same time, two ATP molecules are spent to carry out the reaction in the cell, but 4 ATP molecules are also synthesized. That is, by the method of glycolysis, the cell “earns” only two ATP molecules during the oxidation of 1 glucose molecule. In terms of energy efficiency, this
unfavorable process. During glycolysis, only 5% of the energy of the chemical bonds of the glucose molecule is released.
C 6 H 12 O 6 + 2F inorg + 2ADP 2 C 3 H 4 O 3 + 2ATP + 2H 2 O
Glucose pyruvate
2. The trioses formed during glycolysis (mainly pyruvic acid, pyruvate) are used
are stored for further more efficient oxidation, but already in the cell organelles - mitochondria. At the same time, the energy of splitting is released all chemical bonds, which leads to the synthesis of large amounts of ATP and the consumption of oxygen.
Fig. 40 Scheme of the Krebs cycle (tricarboxylic acids) and oxidative phosphorylation (respiratory chain)
These processes are associated with the oxidative cycle of tricarboxylic acids (synonyms: Krebs cycle, citric acid cycle) and with the electron transfer chain from one enzyme to another (respiratory chain), when ATP is formed from ADP by adding one residue of phosphoric acid (oxidative phosphorylation).
The concept “ oxidative phosphorylation“ determine the synthesis of ATP from ADP and phosphate due to the energy of oxidation of substrates (nutrients).
Under oxidation understand the removal of electrons from a substance, respectively - restoration - the addition of electrons.
What is the role of oxidative phosphorylation in humans? An idea of this can be given by the following rough calculation:
An adult with sedentary work consumes about 2800 kcal of energy per day with food. In order for such an amount of energy to be obtained by ATP hydrolysis, 2800 / 7.3 \u003d 384 mol of ATP, or 190 kg of ATP, will be required. While it is known that the human body contains about 50 g of ATP. Therefore, it is clear that in order to meet the energy demand in the body, these 50 g of ATP must be split and re-synthesized thousands of times. In addition, the very rate of ATP renewal in the body varies depending on the physiological state - the minimum during sleep and the maximum during muscular work. And this means that oxidative phosphorylation is not just a continuous process, but also regulated over a wide range.
The essence of oxidative phosphorylation is the conjugation of two processes, when an oxidative reaction involving energy from outside (exergic reaction) carries along another, endergic reaction of ADP phosphorylation with inorganic phosphate:
A in ADP + F n
oxidation phosphorylation
Here A in is the reduced form of a substance undergoing phosphorylating oxidation,
And o is the oxidized form of the substance.
In the Krebs cycle, pyruvate (CH 3 COCOOH) formed as a result of glycolysis is oxidized to acetate and combines with coenzyme A, forming acetyl-coA. After several stages of oxidation, a six-carbon compound citric acid (citrate) is formed, which is also oxidized to oxal acetate; then the cycle is repeated (Scheme of the cycle of tricarb. Acids). During this oxidation, two CO 2 molecules and electrons are released, which are transferred to acceptor (receptive) molecules of co-enzymes (NAD - nicotinamide dinucleotide) and then are involved in the electron transfer chain from one substrate (enzyme) to another.
With the complete oxidation of one mole of glucose to CO 2 and H 2 O in the cycle of glycolysis and tricarboxylic acids, 38 ATP molecules are formed with a chemical bond energy of 324 kcal, and the total free energy yield of this transformation, as noted earlier, is 680 kcal. The efficiency of the output of stored energy in ATP is 48% (324/680 x100% = 48%).
The overall equation for glucose oxidation in the Krebs cycle and the glycolytic cycle:
C 6 H 12 O 6 + 6O 2 +36 ADP + F n 6CO 2 + 36ATP + 42H 2 O
3. The electrons released as a result of oxidation in the Krebs cycle are combined with a co-enzyme and transported to the electron transfer chain (respiratory chain) from one enzyme to another, where, in the process of transfer, conjugation occurs (transformation of electron energy into the energy of chemical bonds) with the synthesis of molecules ATP.
There are three sections of the respiratory chain in which the energy of the redox process is transformed into the energy of the bonds of molecules in ATP. These sites are called phosphorylation points:
1. The site of electron transfer from NAD-H to the flavoprotein, 10 ATP molecules are synthesized due to the oxidation energy of one glucose molecule,
2. Electron transfer in the area from cytochrome b to cytochrome c 1, 12 ATP molecules are phosphorylated per glucose molecule,
3. Electron transfer in the area of cytochrome c - molecular oxygen, 12 ATP molecules are synthesized.
In total, at the stage of the respiratory chain, 34 ATP molecules are synthesized (phosphorylated). And the total output of ATP in the process of aerobic oxidation of one molecule of glucose is 40 units.
Table 1
Energetics of glucose oxidation
For every pair of electrons passing through the chain from NAD-H + to oxygen, three ATP molecules are synthesized.
The respiratory chain is a series of protein complexes embedded in the inner membrane of mitochondria (Figure 41).
Fig. 41 The layout of the respiratory chain enzymes in the inner membrane of mitochondria:
1-NAD-H-dehydrogenase complex, c 1-complex, 3-cytochrome oxidase complex, 4-ubiquinone, 5-cyto-
chromium-c, 6-mitochondrial matrix, inner mitochondrial membrane, 8-intermembrane space.
So, the complete oxidation of the initial substrate ends with the release of free energy, a significant part of which (up to 50%) is spent on the synthesis of ATP molecules, the formation of CO 2 and water. The other half of the free energy of substrate oxidation goes to the following needs of the cell:
1. For the biosynthesis of macromolecules (proteins, fats, carbohydrates),
2. For the processes of movement and contraction,
3. For active transport of substances across membranes,
4. To ensure the transfer of genetic information.
Fig.42 General scheme of the process of oxidative phosphorylation in mitochondria.
1 - the outer membrane of the mitochondria, 2 - the inner membrane, 3 - the ATP synthetase enzyme built into the inner membrane.
Synthesis of ATP molecules
ATP synthesis occurs in the inner membrane of mitochondria, looking into the matrix (Figure 42 above). Specialized enzyme proteins are built into it, which are exclusively involved in the synthesis of ATP from ADP and inorganic phosphate ATP synthetases (ATP-C). In an electron microscope, these enzymes have a very characteristic appearance, for which they were called “mushroom bodies” (Fig.). These structures completely line the inner surface of the mitochondrial membrane directed to the matrix.
the famous researcher of bioenergetics prof. Tikhonova A.N.,ATF-S is “the smallest and most perfect motor in nature”.
Fig.43 Localization ATP synthetase in the mitotic membrane chondria (animal cells) and chloroplasts (plant cells). Blue areas are areas with an increased concentration of H + (acidic zone), orange areas are areas with a low concentration of H +. Bottom: transfer of hydrogen ions H + through the membrane during the synthesis (a) and hydrolysis (b) of ATP
The efficiency of this enzyme is such that one molecule is able to carry out 200 cycles of enzymatic activation per second, while 600 ATP molecules are synthesized.
An interesting detail of the operation of this motor is that it contains rotating parts and consists of a rotor part and a stator, moreover, the rotor rotates counterclockwise. (Fig. 44)
The membrane part of ATP-C, or conjugation factor F 0 , is a hydrophobic protein complex. The second fragment of ATP-C - conjugation factor F 1 - protrudes from the membrane in the form of a mushroom-shaped formation. In the mitochondria of animal cells, ATP-C is built into the inner membrane, and the F 1 complex is turned towards the matrix.
The formation of ATP from ADP and Fn occurs in the catalytic centers of the conjugation factor F 1 . This protein can be easily isolated from the mitochondrial membrane, while it retains the ability to hydrolyze the ATP molecule, but loses the ability to synthesize ATP. The ability to synthesize ATP is a property of a single complex F 0 F 1 in the mitochondrial membrane (Fig. 1 a) This is due to the fact that ATP synthesis with the help of ATP-C is associated with the transport of H + protons through it in the direction from F 0 rF 1 (Fig. 1 a) . The driving force for the work of ATP-C is the proton potential created by the respiratory electron transport chain e - .
ATP-C is a reversible molecular machine that catalyzes both the synthesis and hydrolysis of ATP. In the mode of ATP synthesis, the work of the enzyme is carried out due to the energy of H + protons transferred under the action of the proton potential difference. At the same time, ATP-C also works as a proton pump - due to the energy of ATP hydrolysis, it pumps protons from a region with a low proton potential to a region with a high potential (Fig. 1b). It is now known that the catalytic activity of ATP-C is directly related to the rotation of its rotor part. It was shown that the F 1 molecule rotates the rotor fragment in discrete jumps with a step of 120 0 . One revolution per 120 0 is accompanied by the hydrolysis of one ATP molecule.
A remarkable quality of the ATF-C rotating motor is its exceptionally high efficiency. It was shown that the work that the motor does when the rotor part rotates by 120 0 almost exactly coincides with the amount of energy stored in the ATP molecule, i.e. Motor efficiency is close to 100%.
The table shows the comparative characteristics of several types of molecular motors operating in living cells. Among them, ATP-C stands out for its best properties. In terms of the efficiency of work and the force it develops, it significantly surpasses all molecular motors known in nature and, of course, all those created by man.
Table 2 Comparative characteristics of molecular motors of cells (according to: Kinoshitaetal, 1998).
The F 1 molecule of the ATP-C complex is about 10 times stronger than the acto-myosin complex, a molecular machine that specializes in performing mechanical work. Thus, many millions of years of evolution before the man who invented the wheel appeared, the advantages of rotational motion were already realized by nature at the molecular level.
The amount of work that ATP-C does is overwhelming. The total mass of ATP molecules synthesized in the body of an adult per day is about 100 kg. This is not surprising, since numerous
biochemical processes using ATP. Therefore, in order for the body to live, its ATP-C must constantly spin, replenishing its ATP reserves in a timely manner.
A striking example of molecular electric motors is the work of bacterial flagella. Bacteria swim at an average speed of 25 µm/s, and some of them swim at over 100 µm/s. This means that in one second the bacterium moves over a distance 10 or more times greater than its own size. If a swimmer covered in one second a distance ten times his own height b, then he would swim a 100-meter track in 5 seconds!
The speed of rotation of the electric motors of bacteria ranges from 50-100 rpm to 1000 rpm, while they are very economical and consume no more than 1% of the cell's energy resources.
Figure 44. Scheme of rotation of the rotary subunit of ATP synthetase.
Thus, both the enzymes of the respiratory chain and ATP synthesis are localized in the inner membrane of mitochondria.
In addition to ATP synthesis, the energy released during electron transport is also stored in the form of a proton gradient on the mitochondrial membrane. At the same time, an increased concentration of H + ions (protons) occurs between the outer and inner membranes. The emerging proton gradient from the matrix to the intermembrane space serves as the driving force in the synthesis of ATP (Fig. 42). In essence, the inner membrane of mitochondria with built-in ATP synthetases is a perfect proton power plant, supplying energy for the life of the cell with high efficiency.
When a certain potential difference (220 mV) across the membrane is reached, ATP synthetase begins to transport protons back to the matrix; in this case, the energy of protons is converted into the energy of the synthesis of chemical bonds of ATP. This is how oxidative processes are coupled with synthetic
mi in the process of phosphorylation of ADP to ATP.
Energetics of oxidative phosphorylation
fat
Even more efficient is the synthesis of ATP during the oxidation of fatty acids and lipids. With the complete oxidation of one molecule of fatty acid, for example, palmitic, 130 ATP molecules are formed. The change in the free energy of acid oxidation is ∆G= -2340 kcal, while the energy accumulated in ATP is about 1170 kcal.
Energetics of oxidative cleavage of amino acids
Most of the metabolic energy produced in tissues is provided by the oxidation of carbohydrates and especially fats; in an adult, up to 90% of all energy needs are covered from these two sources. The rest of the energy (depending on the diet from 10 to 15%) is supplied by the process of oxidation of amino acids (rice of the Krebs cycle).
It has been estimated that a mammalian cell contains, on average, about 1 million (10 6 ) ATP molecules. In terms of all cells of the human body (10 16 –10 17 ) this is 10 23 ATP molecules. The total energy contained in this mass of ATP can reach values of 10 24 kcal! (1 J = 2.39x 10 -4 kcal). In a person weighing 70 kg, the total amount of ATP is 50 g, most of which is consumed daily and re-synthesized.
Control work on the topic "Cell structure" Option 1
A1. chief structural component cell nuclei are
1) chromosomes;
2) ribosomes;
3) mitochondria;
4) chloroplasts.
A2. In plant cells, unlike in animals,
1) chemosynthesis;
2) protein biosynthesis;
3) photosynthesis;
4) lipid synthesis
A3. Has its own DNA
1) Golgi complex;
2) lysosome;
3) endoplasmic reticulum;
4) mitochondrion
A4. Membrane system of tubules that permeates the entire cell
1) chloroplasts;
2) lysosomes;
3) mitochondria;
4) endoplasmic reticulum
A5. Animal cells have a less stable shape than plant cells because they do not have:
1) chloroplasts
2) vacuoles
3) cell wall
A6. Lysosomes are formed on:
1) smooth EPS channels
2) channels of rough EPS
3) tanks of the Golgi apparatus
4) the inner surface of the plasmalemma
A7. Permanent structural basis biological membranes are:
2) carbohydrates
3) nucleic acids
4) phospholipids
A8. An example of active transport of substances across cell membranes is:
3) sodium-potassium pump
4) phagocytosis
A9. The main function of lysosomes:
1) protein synthesis
2) breakdown of organic substances in the cell
3) selective transport of substances
4) storage of hereditary information
A10. Plastids do not include:
1) chloroplasts
2) chromoplasts
3) chromosomes
4) leukoplasts
A) The synthesis of ATP stores in the cell occurs in _______________
B) photosynthesis is carried out in _______________
C) Protein biosynthesis occurs on ______________
D) Selective transport of substances is carried out by __________
FUNCTIONS OF CELL ORGANOIDS
A) Has a two-membrane shell with pores 1) Core
B) stores hereditary information and participates in its transmission 2) Mitochondria
B) Contains a nucleolus in which ribosomes assemble
D) Responsible for the synthesis of ATP
E) Contains karyoplasm
Answer in the form: A1B2V1 ...
C1. What cells are shown in the pictures? /Give comparative characteristic these cells/
Rice. 1 Fig. 2 Fig. 3
Control work on the topic "Cell structure" Option 2
A (choose one correct answer)
A1. Cytology is the science of
3) protozoa
4) about a person
A2. What cell organelles can be seen in a school light microscope
1) lysosomes
2) ribosomes
3) cell center
4) chloroplasts
A3. The main component of the plant cell wall is
1) starch
3) cellulose
4) glycogen
A4. The similarity of the structure of cells of autotrophic and heterotrophic organisms is that they have
1) chloroplasts
2) plasma membrane
3) cellulose shells
4) vacuoles with cell sap
A5. The endoplasmic reticulum performs the following functions
1) synthetic and protective
2) protective and reserve
3) transport and protective
4) transport and synthetic
A6. The essence of the cell theory is most accurately reflected in the paragraph:
1) plant organisms are made up of cells
2) animals are made up of cells
3) all both lower and higher organisms are composed of cells
4) the cells of all organisms are the same in structure
A7. The species affiliation of a eukaryotic cell is indicated by:
1) the presence of a nucleus in the cell
2) number of chromosomes
3) the number of nuclei in the cell
4) cell sizes
A8. Anthony Leeuwenhoek could see through his microscope:
1) mitochondria
2) endoplasmic reticulum
3) cell nucleus
4) ribosomes
A9. DNA in representatives of cellular life forms is located:
1) in the nucleus or cytoplasm
2) in chloroplasts
3) in mitochondria
4) in all of the above
A10. The accumulation of starch occurs in plastids:
1) chloroplasts
2) leukoplasts
3) chromoplasts
4) in all of the above
IN 1. Complete the following phrases:
A) Leukoplasts in the light turn into __________
B) The organelles of movement are ______________
C) The set of chromosomes contained in the cells of an organism is called __________
D) The synthesis of ATP reserves is carried out in the organoid _________________
Answer in the form: A1B2V1 ...
IN 2. Establish a correspondence between the organelles of the cell and their functions.
FUNCTIONS OF CELL ORGANOIDS
A) Participates in the transport and synthesis of substances 1) Ribosomes
B) Can be smooth or rough 2) EPS
B) Consists of two subunits
D) Formed by ribonucleic acids and proteins
D) Responsible for protein synthesis
E) Bacteria have
C1. What organelles are shown in the drawings (photos)? / In the cells of what living organisms are they present and what functions do they perform? /
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Rice. 1 Fig. 2 Fig. 3 Fig. four
Lesson number 9
Topic: “Metabolism in the cell. Energy and plastic exchanges”.
1. Metabolism and energy conversion in a cell is the basis of its life activity.
2.Plastic and energy exchange.
3. Stages of energy metabolism.
4. Photosynthesis. Phases of photosynthesis.
5. Chemosynthesis and its significance.
Any living organism, like a single cell, is open system, i.e.
exchanged with environment matter and energy. So, we know that the body needs energy to sustain life. We store and spend energy - and this process is endless as long as there is life. The main source of energy for all living beings is the energy of sunlight. The sun is the primary source of energy. Living beings are able to use two types of energy: light (energy solar radiation) and chemical (bond energy of chemical compounds) - on this basis, organisms are divided into two groups - phototrophs and chemotrophs.
Experiments have shown that the contents of the cell are in a state of continuous activity; various substances enter the cell all the time and leave it outside, i.e. metabolism is the basis for the existence of living organisms. The whole set of enzymatic reactions metabolism and energy occurring in the body are called metabolism (Greek "metabole" - transformation).
Metabolism is the basis of cell life.
Metabolism consists of interrelated reactions:
Metabolism = Anabolism + Catabolism
assimilation dissimilation
(synthesis of macromolecular compounds - (cleavage and oxidation of organic
proteins, nucleic acid, polysaccharides, lipids) things that go with the conversion of energy)
plastic metabolism energy metabolism
Metabolism is understood as the exchange of substances and energy constantly occurring in the cells of living organisms. Some connections, having fulfilled their function, become unnecessary, in others there is an urgent need. In various metabolic processes, macromolecular compounds are synthesized from simple substances with the participation of enzymes, in turn, complex molecules are split into simpler ones. A huge number of synthesis processes take place in the cell: lipids in the endoplasmic reticulum, proteins on ribosomes, polysaccharides in the Golgi complex. To ensure synthesis reactions, the cell requires significant expenditures of energy obtained from the breakdown of substances.
Metabolism performs two functions.
First- providing the cell with building material (synthesis reactions of new complex substances from simpler ones). Synthesis reactions are especially active in young cells, but these processes also occur in mature cells - molecules that have been destroyed in the process of vital activity are replaced by new ones.
The set of reactions that ensure the construction of the cell and the renewal of its composition is called plastic metabolism. . All these are reactions of biological synthesis, called anabolic (Greek: anabole rise), and their combination in a cell is called anabolism.
Second The function of metabolism is to provide the cell with energy.
For the energy supply of the cell, the energy of chemical bonds is used, which is released during the breakdown of various substances. This energy is converted into other forms of energy.
The set of reactions of splitting complex molecules into simpler ones is called catabolism or energy metabolism.
Examples of such reactions are the breakdown of lipids, polysaccharides, proteins and nucleic acids in lysosomes, as well as simple carbohydrates and fatty acids in mitochondria.
Plastic and energy metabolism of the cell are interconnected. On the one hand, all synthesis reactions require energy, and on the other hand, energy metabolism reactions require a constant synthesis of enzymes, because they break down quickly.
Enzymes - these are biologically active substances of a protein nature that accelerate chemical reactions in the cell (biological catalysts) by forming intermediate compounds.
Through plastic and energy exchanges, the cell is connected with the external environment. These processes are the main condition for maintaining the life of the cell, the source of its growth, development and functioning.
Energy metabolism in the cell. Synthesis of ATP.
Adenosine triphosphoric acid (ATP) is the source of energy in living cells, providing all types of their activities. The energy released during the splitting of ATP provides any kind of cellular functions - movement, biosynthesis, transport of substances through membranes, etc. T, to. Since the supply of ATP in the cell is small, it is clear that as ATP decreases, its content must be restored. In fact, this is what happens. The biological meaning of the remaining reactions of energy metabolism lies in the fact that the energy released as a result of chemical reactions of oxidation of carbohydrates and other substances is used to synthesize ATP, i.e., to replenish its supply in the cell. During intense, but short-term work, for example, when running a short distance, the muscles work almost exclusively due to the breakdown of the ATP they contain. After the end of the run, the athlete breathes heavily, warms up: during this period, intensive oxidation of carbohydrates and other substances occurs to replenish the loss of ATP consumed. With prolonged and not very hard work, the ATP content in the cells may not change significantly, since the oxidation reactions have time to ensure a quick and complete recovery of the spent ATP.
So, ATP is a single and universal source of energy for the functional activity of the cell. From this it is clear that it is possible to transfer energy from one part of the cell to another and harvest energy for future use. ATP synthesis can occur in one place of the cell at one time, and it can be used in another place and at another time.
ATP synthesis is carried out mainly in mitochondria. That is why mitochondria are called the "powerhouses" of the cell. The ATP formed here is sent through the channels of the endoplasmic reticulum to those parts of the cell where there is a need for energy.
So, the source of energy for the vast majority of processes in living organisms is the following reaction:
ATP + H2O = ADP + H3PO4 + energy.
ATP attaches a water molecule and breaks down. The terminal phosphorus residue gives phosphoric acid, and ATP is converted to ADP. This reaction is accompanied by the release of energy (about 40 kJ / mol)
- It is known that the average content of ATP in cells is from 0.05% to 0.5% of its mass. But almost all biochemical reactions taking place in the cell require the energy of ATP molecules. The supply of ATP in the muscles is only enough for 20-30 contractions. Therefore, in the cells there is a constant process of ATP synthesis.
Therefore, the supply of ATP must be continuously replenished based on the reverse reaction that comes with the expenditure of energy:
ADP + H3PO4 + energy = ATP + H2O.
Energy metabolism - a set of reactions of oxidation of organic substances in the cell, the synthesis of ATP molecules due to the released energy. The value of energy metabolism is the supply of energy to the cell, which is necessary for life.
The role of ATP in the life of the organism as a whole cannot be overestimated. Among the most important consumers of ATP, it should be noted such as:
1. Most anabolic reactions ( anabolic reactions ) pass through cells using ATP, i.e.:
Synthesis of proteins from amino acids,
Synthesis of DNA and RNA from nucleotides,
Synthesis of polysaccharides,
Synthesis of fats
2. ATP is necessary for active transmembrane transport of molecules and ions,
for the induction and conduction of a nerve impulse nerve impulses),
maintenance of cell volume through the mechanisms of osmosis ( osmosis),
for muscle contractions muscle contraction),
for the implementation of bioluminescence in tissues ( bioluminescence).
3. ATP is a synaptic transmitter widely distributed in various
organs, especially in the presynaptic endings of effector neurons. When these endings are stimulated, purine decay products - adenosine and inosine - are released. In evolutionary biology, it is generally believed that ATP was the only and common mediator for all organisms in the early stages of evolution. In the process of evolution, due to the complication of the structure of organisms, new specialized synaptic mediators began to appear. Studies on individual organs of experimental animals have shown that ATP promotes relaxation of the smooth muscles of the digestive organs.
Heart Energy Disorders: Causes and Consequences
One of the most important channels of energy consumption in the human body is the activity of the heart. Continuous work of the heart (C) requires sustainable and reliable energy consumption. A blockage in one of the self-supplying arteries cuts off the blood supply to a portion of the heart muscle and tissue ischemia occurs. A long period of ischemia leads to the death of heart muscle cells, cardiomyocytes - then myocardial infarction develops. But, if the vasospasm was short-lived, and the blood flow in it is restored, then the contractile work of the myocardium can be fully restored. This problem has become especially important in connection with the development of heart transplant technology. How is the supply of energy to the cells of the heart muscle and its use carried out?
Fig.45 The main energy-consuming structures of the cardiomyocyte.
The contractile function of cardiomyocytes is regulated by calcium ions. They enter the cell from the outside and cause the release of calcium ions contained in the cisterns of the sarcoplasmic reticulum. These ions bind to myofibrils and cause them to contract.
The main consumer of ATP in cardiomyocytes is the contractile apparatus of myofibrils (Fig. 45); its energy requirement is estimated at about 80% of the total energy consumption. Approximately 10-15% of energy is spent on maintaining the transmembrane potential and excitability of cardiomyocytes. And about 5% of the cell's energy is used for synthetic processes. In addition to ATP, another high-energy compound, creatine phosphate (Kf), can be a source of energy in cells, which is more efficiently used by the cell than ATP.
The process of energy formation in cardiomyocytes is disturbed for various reasons. With sudden myocardial ischemia, ATP synthesis in mitochondria stops, the content of Kf and ATP rapidly decreases. At the same time, the functions of the contractile apparatus are most deeply violated.
Protective mechanisms in ischemia.
The development of ischemia in the heart muscle includes protective mechanisms that reduce destructive processes.
1. ATP-dependent potassium channels open (Figure 46). Normally, they are closed, and with insufficient ATP re-synthesis, they open and potassium actively leaves the cells. This is accompanied by a decrease in membrane potential and cell excitability.
Fig.46. Metabolic consequences of myocardial ischemia
2. Acidification of the cytoplasm of cells occurs - acidosis develops. The termination of oxidation in mitochondria during ischemia leads to the activation of glycolysis, the accumulation of underoxidized products,
an increase in the concentration of hydrogen ions and a shift in pH.
3. The breakdown of ATP and Kf is accompanied by the accumulation of phosphate in the heart cells. This reduces the sensitivity of contractile proteins to Ca +2 ions.
4. Accumulation of adenosine as a result of ATP breakdown blocks adenoreceptors on cardiomyocytes. As a result, the neurotransmitter norepinephrine does not activate the heart cells and prevents the decrease in ATP and Kf reserves.
Thus, already at the beginning of the ischemia stage, several protective mechanisms are activated that reduce the entry of calcium ions into cardiomyocytes and the sensitivity of the contractile apparatus to the action of calcium ions. During ischemia, the level of contractile function drops very quickly (within 30 seconds) to about 5-10% of the initial level, while the content of AVTP and Kf decreases moderately. This allows the heart cells to use energy economically and survive the unfavorable period. With prolonged ischemia (several hours), energy deficiency worsens, acidosis increases - this leads to the destruction of cell organelles and cell necrosis.
The sudden suppression of ATP synthesis during ischemia could cause the death of cardiomyocytes within a few minutes if the natural defense mechanisms in the heart did not work. They quickly suppress contractile activity and provide economical use of energy reserves for tens of minutes. Elimination of the causes that caused ischemia during this period can restore cardiomyocyte contractility and heart function.
The ischemia zone can be reduced by introducing adenosine, potassium ions, and nitric oxide NO, which has a vasodilating effect. It turned out that it is nitric oxide that mediates the action of many vasodilators, such as nitroglycerin.
cell nucleus
The term "nucleus" was coined by Brown in 1833 when he first described the permanent globular structures in plant cells. Later, the same structures were found in all cells of higher organisms, including humans.
The cell nucleus, usually one per cell, consists of nuclear envelope separating it from the cytoplasm chromatin, nucleolus, nuclear protein matrix(backbone) and karyoplasms(nuclear juice) (Figure 27 Chentsov).
Granular endoplasmic reticulum nuclear time
ribosomes
Fig.47. cell nucleus
These components of the nucleus are present in all eukaryotic cells - unicellular and multicellular.
Nucleus(nucleus) cells - a structure containing genetic information about the cell and the whole organism. The nucleus performs two groups of general functions: 1- storage of genetic information., 2- its implementation in the form of protein synthesis.
1. Storage and maintenance of hereditary information in the form of an unchanged DNA structure is associated with the work of the so-called. repair enzymes that eliminate spontaneous damage to DNA molecules. Repair enzymes also work in cells damaged by radiation, contributing to a more or less effective recovery of cells from radiation damage. This type of reparation was discovered by the famous Obninsk radiobiologist prof. Luchnik N.V. in the 70s of the 20th century.
2. Another side of the activity of the nucleus is the work of the apparatus of protein synthesis. Ribosome components are also synthesized in the nucleus. From the general scheme of protein synthesis (Fig. 16 Chentsov), it can be seen that the source of information for the start of biosynthesis is DNA
Structure and chemical composition cell nucleus
The vast majority of cells of higher mammals contain only one nucleus, although there are also multinucleated cells - for example, muscle fiber cells - myosymplasts.
nuclear chromatin is a dense substance that fills almost the entire volume of the nucleus. In non-dividing (interphase) cells, it is diffusely distributed over the volume of the nucleus; in dividing cells, it is compacted (condensed) and forms dense structures - chromosomes. Chromatin stains well with basic dyes. , therefore, it got its name (from the Greek chroma - color, paint). As part of chromatin - DNA in a complex with proteins - histone (alkaline) and non-histone. Diffuse chromatin of interphase nuclei of genetics is called euchromatin, condensed chromatin heterochromatin. In both forms, chromatin is fibrils 20–25 nm thick.
It is known that the length of individual DNA molecules can reach hundreds of microns and even approach a centimeter. In the human chromosome set, the longest chromosome is the first, up to 4 cm long. Chromosomes have many places of independent replication (doubling) - replicons. Thus, DNA is a chain of tandemly arranged replicons of various sizes.
Chromatin proteins make up 60-70% of its dry weight. Histones (alkaline proteins) are not evenly distributed along the DNA molecule, but in the form of blocks, each of them includes eight histone molecules, forming a structure nucleosome. The process of nucleosome formation is accompanied by DNA supercoiling and a shortening of its length by about 7 times.
In the nucleus, in addition to DNA, there are also molecules of RNA information associated with proteins.
Chromosomal cycle
It is well known that sexual female and male cells carry a single set of chromosomes and therefore contain 2 times less DNA than other cells of the body. Sex cells with a single set of chromosomes are called haploid. Ploidy, i.e. multiplicity, is denoted in genetics by the letter n. Thus, cells with the 1n set are haploid, with 2n diploid, and with 3n are triploid. Accordingly, the amount of DNA in a cell (denoted by the letter c) depends on its ploidy: cells with 2n-number of chromosomes contain 2c amount of DNA. During fertilization, two haploid cells merge, each of which carries a set of 1n chromosomes, therefore diploid(2n,2c) cell is a zygote. Then, due to the division of the diploid zygote and the subsequent division of diploid cells, an organism will develop, the cells of which will be diploid, and some of them (sexual) will again be haploid.
However, the process of division of diploid cells is preceded by the DNA-replication phase of synthesis, i.e. cells appear with the amount of DNA equal to 4c, they have the number of chromosomes - 4 n. And only after the division of such a tetraploid (4c) cell, two new diploid cells appear.
It is difficult to see the chromosomes in the nuclei of interphase (resting) cells. They appear in the nucleus shortly before cell division. In interphase, however, there is a doubling, reduplication of chromosomes. During this period, DNA synthesis occurs, so it is called the synthetic, or S-period. During this period, the amount of DNA greater than 2s is detected in the cells. After the end of the S-period, the amount of DNA in the cell is 4s (complete doubling of the chromosomal material). If you count the number of chromosomes in prophase, then there will be 2n, but this is a false impression. at this time, each chromosome is double (as a result of reduplication). At this stage, a pair of chromosomes are in close contact with each other, they twist one around the other. Therefore, already at the beginning of prophase, the chromosomes consist of two sister chromosomes - chromatids. They remain connected to each other in the next phase - metaphase, when the chromosomes line up in the equatorial plane of the cell. In the next stage - anaphase, there is a divergence of pairs of homologous chromosomes to opposite poles of the cell, after which the cell divides. Then, in the telophase, the separated diploid sets (2n) of chromosomes begin to decondense, i.e. loosen up. This is how one chromosome cycle ends and the next one begins (Fig. 31 Chentsov). The chromosome (cellular) cycle in multicellular eukaryotes lasts 1-1.5 days.
Nucleolus (Nucleolus)
In the nucleus of all eukaryotic cells, one or more rounded bodies are visible - the nucleoli. They stain well with basic dyes because they are rich in RNA. The nucleolus is a derivative of chromosomes, while it is an independent organelle, the function of which is to form ribosomal RNA and ribosomes. The nucleolus is heterogeneous in structure - the central part is fibrillar, where ribosome precursors are concentrated, and the periphery is granular, where maturing ribosome subunits are concentrated.
Nuclear envelope (karyolemma)
It is a structure that limits the cell nucleus. It separates two intracellular components from each other - the nucleus from the cytoplasm. The significance of such a separation of structures in space is important: it creates additional (in comparison with prokaryotes) opportunities for the regulation of gene activity during the synthesis of specific proteins.
The nuclear membrane consists of two membranes - outer and inner, between which is located the perinuclear space (Fig. 106 Chentsova). In general, the nuclear membrane can be represented as a two-layer bag that separates the contents of the nucleus from the cytoplasm. However, the nuclear membrane has a characteristic feature that distinguishes it from other membrane structures of the cell - these are special nuclear pores formed by the fusion of two nuclear membranes.
The outer membrane of the nuclear membrane is referred to as the membrane system of the endoplasmic reticulum - numerous polyribosomes are located on it, and the nuclear membrane itself passes into the membranes of the reticulum. The inner membrane of the nuclear envelope does not have ribosomes on its surface. However, it is associated with chromatin and is a characteristic feature of the inner nuclear membrane.
Another function of the nuclear envelope is the creation of an intranuclear order, architecture, the fixation of chromosomal material in three-dimensional space.
Nuclear pores are the result of the fusion of two nuclear membranes. The pore openings are about 90 nm in diameter. The nuclear pore complex, which includes 8 peripheral protein granules and one central one, is involved in the transport of protein and nucleoprotein molecules and in the recognition of these molecules. This transport process is active and requires ATP. On average, there are several thousand pore complexes per core (Fig. 109 Chents).
Nuclear protein matrix
The processes of replication (doubling) and transcription (reading information) of chromatin are carried out in the nucleus in a strictly ordered manner. To implement these processes, there is an intranuclear system that combines all nuclear components - chromatin, nucleolus, nuclear envelope. Such a structure is the nuclear protein backbone, or matrix (NBM). At the same time, it does not represent a clear morphological structure. According to the morphological composition, JBM consists of three components: a reticular protein layer - lamina, an internal network - backbone, and a “residual” nucleolus. The main component of the NBM structures is fibrillar proteins, similar in amino acid composition to intermediate microfilaments.
The role of the nuclear envelope in nuclear-cytoplasmic metabolism.
The nuclear membrane serves as a regulator in the nuclear-cytoplasmic exchange. The exchange of products between the nucleus and the cytoplasm is very large: all nuclear proteins enter the nucleus from the cytoplasm, and all RNAs are removed from the nucleus. The complexes of nuclear pores in this process play the role of not only a transfer mechanism (translocator), but also the role of a sorter of the transported material. Through the pores, ions, sugars, nucleotides, ATP and hormones enter the nucleus by passive transport. High-molecular compounds with a mass of no more than 5.10 3 Da penetrate the nuclear membrane in both directions by the method of passive transport. Active transport of macromolecules in both directions is also carried out through nuclear pores.
non-membrane organelles.
Ribosomes. These specialized cell organelles provide for the synthesis of proteins and polypeptides. They are present in all types of animal cells and are high molecular weight ribonucleoproteins. Ribosomes (R) are composed of proteins and a special type of RNA called ribosomal RNA (r-RNA). P size - 20 x 20 x 20 nm. Consists of large and small subunits. Each of the subunits is formed from a ribonucleoprotein strand. Cells contain individual R and their complexes - polyribosomes. They can be freely located in the hyaloplasm or be associated with the membranes of the endoplasmic reticulum. Usually, free P is contained in unspecialized and rapidly growing cells, while those associated with the reticulum are found in specialized cells. In addition, free Ps synthesize protein for the cell's own needs, while bound Ps synthesize it for export.
Rice. "Bunch" ribosome
cytoskeleton. This is the musculoskeletal system in the cell, creating a truly cellular skeleton (Fig). The system contains protein filamentous formations. Filamentous and fibrillar structures of the cytoskeleton are dynamic formations that arise and disappear depending on the functional state of the cell. The main components of the cytoskeleton are microtubules and microfilaments.
Using immunofluorescence methods, it was established that the composition of microfilaments includes contractile proteins - actin, myosin, tropomyosin. That is, microfilaments are nothing but the contractile apparatus of the cell, which ensures the mobility of both the cell itself and the organelles inside it. Microfilaments have a thickness of 5-7 nm.
Microtubules are involved in the creation of temporary (division spindle, cytoskeleton of interphase cells) and permanent structures (centrioles, cilia, flagella). They are straight non-branching hollow cylinders with a diameter of 24 nm, the wall thickness of the cylinder is 5 nm. In an electron microscope, 13 subunits of the tubulin protein are visible on a cross section of microtubules.
Cell center (centrosome). Consists of centrioles and associated microtubules. Using electron microscopy methods, it was possible to study the fine structure of centrioles. This structure is based on 9 triplets of microtubules forming a hollow cylinder (Fig.). Its width is about 2 nm, length - 3-5 nm.
Usually, two centrioles are present in interphase cells, forming a single structure - a diplosome. In it, the centrioles are located at right angles to each other. Of the two centrioles, maternal and daughter centrioles are distinguished. The end of the daughter centriole is directed towards the surface of the parent centriole.
In preparation for mitotic division, the centrioles double in the cell. It is interesting that the increase in the number of centrioles is not associated with their division, budding, or fragmentation, but is the result of the formation of the primordium next to the original centriole.
Prior to mitosis, centrioles serve as the center for the formation of the microtubule spindle.
In addition to these structures, some cells include cilia and flagella, which are outgrowths of the cytoplasm. Inside these outgrowths there is a complex contractile system of microtubules and contractile proteins such as tubulin and dynein. With the help of cilia and flagella, cells carry out movement.
Lecture 5
The whole variety of transformations of substances in cells is made up of chains of biochemical reactions. For the implementation of biochemical reactions, the entry of substances into the cell is necessary - endocytosis, transformation of substances in the cell - metabolism, and the removal of end products of metabolism in the form of unnecessary slags or biologically active substances necessary for the body - exocytosis.
Endocytosis. There are several ways to implement endocytosis:
Transmembrane passive and active transport of substances into the cell. This form of endocytosis is described in the corresponding chapter.
Pinocytosis is the capture of liquid colloidal particles by the cell.
Phagocytosis is the capture by a cell of dense and large corpuscular particles up to the capture of other cells.
In general, the entry of solid or liquid substances into the cell from the outside is called the general term - heterophagy. This process is important for the human body in such organs and systems as protective (phagocytic activity of blood neutrophils, macrophages), rearrangements in bone tissue (osteoclasts), the formation of the hormone thyroxine in the thyroid follicles, reverse absorption of protein and other macromolecules in the tubules of the kidney nephron.
Cellular metabolism, or metabolism, is a set of processes for the biosynthesis of complex biological molecules from simpler ones (assimilation) and reactions for the breakdown of complex macromolecules with the release of thermal energy used by cells for various purposes (dissimilation).
The cell efficiently uses the energy contained in the chemical bonds of proteins, carbohydrates and fats supplied with food, and released during their breakdown (hydrolysis) in the digestive tract. That is, cellular metabolism is carried out according to the rules of the first law of thermodynamics - energy does not arise and is not destroyed, it passes from one form to another, suitable for doing work.
Schematically, the processes of dissimilation of nutrients occur in such a way that at the initial stage in the digestive tract they are broken down to monomers (proteins to amino acids, fats to fatty acids, carbohydrates to monosaccharides), after which, regardless of the nature of nutrients, further
Exocytosis. Removal of substances from cells is also carried out using several mechanisms. As well as endocytosis, active and passive transport of substances from the cell takes place. Active transport removes ions and small molecules, passive - most inorganic substances and end products of metabolism (so-called slags).
Another method of excretion is available for the removal of large molecular compounds from cells. They accumulate in the cytoplasm in the Golgi apparatus in the form of transport vesicles and, with the help of a system of microtubules, are concentrated at the plasma membrane of the cell. The vesicle membrane is embedded in the plasma membrane, and the contents of the vesicle are expelled outside the cell. The fusion of the vesicle with the plasma membrane can occur without any additional signals - such exocytosis is called constitutive. In this way, as a rule, the products of the cell's own metabolism, or waste products, are removed. But a significant part of the cells synthesizes special substances necessary for the body to live - secrets. In order for the bubble with the secret to merge with the plasmalemma, a signal from the outside is needed. This exocytosis is called adjustable. Signaling molecules stimulating the excretion of secretions are called liberins, inhibiting the excretion are called statins. This method of exocytosis in the neuroendocrine system during the production of hormones and neurotransmitters is very common.
Intercellular interactions
Cell Functions
Reproduction of cells. Cell cycle.
According to one of the postulates of the cell theory, cell reproduction, i.e. an increase in their number occurs by dividing the original cell. This rule is true for both eukaryotic and prokaryotic cells. The lifetime of a cell as such, from division to the next division, or from division to its death, is called cell cycle . In the body, cells of different tissues and organs have an unequal ability to divide. For example, in all organs there are cell populations that have completely lost the ability to divide. These are specialized, or differentiated, cells. They perform, as a rule, special functions inherent only to this type of cells and are part of the parenchyma of organs.
But in the body there are constantly renewing tissues - epithelial, hematopoietic tissues. In such tissues, there is a fairly large proportion of actively dividing cells that replace obsolete ones. The duration of the cycle is usually 10-30 hours in actively dividing cell populations. Dividing cells have a different amount of DNA depending on the stage of the cell cycle. This is typical for both sex and somatic cells. It is known that male and female germ cells carry a single (haploid) set of chromosomes and contain two times less DNA than somatic diploid cells of the whole organism. Ploidy in genetics is denoted by the letter n . So, germ cells have 1n set, somatic cells have 2n set, i.e. they are diploid, there are cells with a set of chromosomes 3n - this is a triploid set.
During the cell cycle, in a population of diploid cells, both diploid and tetraploid sets of chromosomes and intermediate amounts of DNA during the cell's rest period (interphase) occur. Such heterogeneity is due to the fact that the doubling of the amount of DNA occurs before the onset of division (mitosis).
Whole cell cycle(animation on the Internet) consists of four time periods: mitosis itself (M), presynthetic (G 1), synthetic (S) and postsynthetic (G 2) periods of interphase.
In the G 1 period, which follows immediately after mitosis, the cells have a diploid DNA content (2c; c is the DNA content corresponding to ploidy). During this period, cell growth begins due to the accumulation of cellular proteins and the cell is prepared for the synthetic period S. It is during this period that the synthesis of enzymes is activated,
necessary for the formation of DNA precursors. The energy demand in the cell increases sharply.
In the S-period, the amount of DNA doubles (reduplication) and the number of chromosomes doubles (1n---2n). In different cells in the S-period, you can also find a different amount of DNA - from 2 s to 4 s. During this period, the RNA content increases in accordance with the amount of DNA.
The postsynthetic G 2 phase is also called pre-mitotic. During this period, the synthesis of messenger RNA is activated, which is necessary for the implementation of mitosis.
At the end of this period, before mitosis, RNA synthesis falls.
In the growing tissues of animals and plants there are a certain number of cells that are, as it were, outside the cell cycle. These cells are called cells G 0 - period, or resting. They do not enter the next stage -G 1 after mitosis, but stop dividing. At the same time, they do not differentiate, remaining in a state ready for mitosis. For example, most liver cells are in the G 0 - period - they do not synthesize DNA and do not divide. However, after removal of a part of the liver, as shown in experimental conditions in animals, most of the liver cells are included in the mitotic cycle. Many cells completely lose the ability to return to the mitotic cycle - for example, brain neurons.
Cell cycle and radiosensitivity
It is interesting to note that different stages of the cell cycle differ significantly in sensitivity to external influences. For example, the most sensitive to chemical agents and physical influences, such as ionizing radiation, G 1 - period and mitosis itself, while the main part of the interphase (G 2 and S periods) is less sensitive. Experimental studies on cell cultures obtained from irradiated animals have shown that differences in radiosensitivity can reach 40 or more times between stages of the cell cycle. In addition, in cells exposed to radiation, the time indicators of individual stages of the cycle change; for example, there is a delay in the onset of the mitotic stage and an elongation of the G 2 stage.
In radiation cytology, phenomena of spontaneous restoration of the vital activity of irradiated cells from potentially lethal damage are known. This effect was discovered by the Russian researcher V.I. Korogodin in the 50s of the 20th century and was essential for assessing the true radiosensitivity of cells and the organism as a whole.
Cell division: mitosis.
Mitosis (karyokinesis, indirect division) - a universal way of dividing any eukaryotic cells (animated film on the Internet). Already synthesized in the previous pre-mitotic period G 2 chromosomes (double set - 4n) pass into a condensed compact form, a division spindle is formed in the cell and homologous chromosomes separate to opposite poles of the cell, after which the cytoplasm of the cell is also divided (cytokinesis, cytotomy).
The process of mitosis is conditionally divided into several main phases: prophase, metaphase, anaphase, telophase.(rice)
Prophase. As already noted, at the end of the S-period, the amount of DNA in the interphase nucleus of the cell is 4 s, since the doubling of the chromosomal material has already occurred. However, morphologically, in a light microscope, the number of chromosomes in prophase differs as 2n, although each of them has already doubled. However, by the end of the prophase, the duality of the set of chromosomes is already morphologically distinguishable due to the actively ongoing process of condensation (densification) of chromosomes. The number of chromosomes 4n exactly corresponds to the amount of DNA - 4 s.
prophase
prometaphase
telophase
metaphase
anaphase
Rice. Mitosis
In prophase, the level of synthetic processes in the cell is significantly reduced, and a division spindle is formed - an apparatus for diluting genetic material to two poles of the cell.
Metaphase. This phase takes about a third of the total time of mitosis. Its distinguishing feature is that at this time the formation of the division spindle ends and the chromosomes line up in the equator of the division spindle in the middle of the cell. The cell in this phase has a characteristic appearance called the “metaphase plate”, or parent star. By the end of the metaphase, doubled and condensed chromosomes are already clearly visible in the light microscope in the form of closely adjacent sister chromatids. Their arms are parallel to each other, but there is already a separating space between the chromatids.
Anaphase. Homologous chromosomes lined up in the center of the cell lose their connection with each other and synchronously begin to diverge to opposite poles of the cell that has not yet divided. This is the shortest phase of mitosis. Nevertheless, important events take place at this time: the separation of two identical sets of chromosomes and their movement to the two poles of the cell.
Telophase. Two sets of chromosomes (2nx2) form two cell nuclei; at the same time, the process of division of the original cell into two daughter cells is going on - cytokinesis, cytotomy. In the submembrane layer of the cytoplasm, contractile proteins such as actin fibrils are located, oriented in the zone of the cell equator. These proteins carry out the “constriction” of the cell in the center and its division into two daughter cells. Mitosis is completed.
If the mitotic apparatus is damaged, mitosis may be delayed in metaphase or even chromosomes may scatter. In addition, multipolar and asymmetric mitoses may occur. When cytotomy processes are disturbed, giant nuclei or multinucleated cells are formed. Such effects are observed during malignant transformation of cells both under the influence of external sources (chemical agents, drugs, ionizing and non-ionizing radiation, viruses) and under the influence of internal factors (for example, some hormones, biologically active ingredients).
Meiosis
In addition to the mitotic division of somatic cells, which occurs in all organs and tissues of the body, there is a special, unique form of cell reproduction, leading to the formation of germ cells with a haploid set of chromosomes. This form is called meiosis and it occurs in higher animals (and humans) and higher plants in the primary generative organs. In humans, the formation of germ cells (gametes) occurs in the testicles (in men) and ovaries (in women).
The formation of male germ cells (spermatogenesis) proceeds in the tissue of the convoluted seminiferous tubules of the testicles and includes 4 successive stages: reproduction, growth, maturation and formation (Fig.).
The initial phase of spermatogenesis reproduction spermatogenic epithelium and the formation of more mature cells - spermatogonia. Among the spermatogonia there is a pool of stem cells, which are the source of the formation of new cells, and the other part of the spermatogonia continues further maturation, or differentiation.
The result of this maturation (phase growth) is the loss of the cell's ability to divide, the formation of a cell called the primary spermatocyte, or spermatocyte of the 1st order. During this period, the spermatocyte of the 1st order increases in volume and enters the stage of the first division of meiosis (reduction division). This stage is long and consists of 5 stages: leptotenes, zygotenes, pachytenes, diplotenes and diakinesis. After division, each of the two daughter cells, called second-order spermatocytes, or secondary spermatocytes, already contains a haploid number of chromosomes (23 in humans).
The next phase is the second division (phase maturation), occurring as a normal mitosis in secondary spermatocytes without reduplication (doubling) of chromosomes. As a result, four cells with a haploid chromosome set-spermatids are formed from two secondary spermatocytes. Thus, each initial spermatogonia gives rise to 4 spermatids, which have a haploid (single) set of chromosomes.
Spermatids no longer divide and, after complex morphological changes, turn into mature spermatozoa. This transformation occurs in the final stage of spermatogenesis - the phase formation sperm.
spermatogonia (diploid cell)
mitosis
Additional spermatogonia
Primary spermatocyte
first meiotic division
Secondary spermatocyte
Second meiotic division
Spermatids (haploid cells)
Sperm
Head
Neck
Tail
Rice. spermatogenesis
The process of spermatogenesis in humans lasts about 75 days and proceeds along the convoluted seminiferous tubule in waves. In a certain section of the tubule there is a certain set of cells of the spermatogenic epithelium.
Lecture 6 . Cell responses to external influences.
The cells of the body are constantly exposed to various environmental factors - chemical, physical and biological, as well as internal influences - nervous and neuro-humoral. These factors cause primary disorders in cellular structures, as a result of which, as a rule, a functional disorder is observed in an organ or system. The fate of cells depends on the intensity of exposure, its nature and duration. After violations, cells can adapt, adapt to the influencing factor, recover after the cancellation of the damaging effect, or irreversible changes will eventually lead to cell death.
With reversible damage, cells respond with a number of functional and morphological changes. One of the most common criteria for cellular damage is a change in the ability of cells to interact with various dyes. Normal cells absorb dyes dissolved in water and deposit them as granules in the cytoplasm; the core is not stained. Damaged cells (due to heating, changes in pressure, pH of the medium, exposure to a denaturing agent) lose this ability and the dye is diffusely distributed not only in the cytoplasm, but also in the nucleus. In the case of a reversible nature of damage, subject to the cancellation of the action of an external factor, granulation in the cytoplasm of cells is restored.
Another characteristic sign of cell damage is a drop in the respiratory processes in the cell, with a significant drop in oxidative phosphorylation, which is necessary for ATP synthesis. Damaged cells are characterized by an increase in glycolytic processes (acidification), a decrease in the amount of ATP and activation of proteolysis (protein denaturation). The whole set of non-specific reversible changes in cells that occur under the action of various agents is called "paranecrosis". In this initial and reversible stage of changes, the processes of cellular assimilation and dissimilation are not significantly changed.
However, in the case of irreversible damage to cellular metabolism, events unfold that affect not only the cytoplasm, but also the nuclear apparatus. The most significant manifestation of irreversible changes in a damaged cell is the condensation (densification, aggregation) of chromatin, the fall of nuclear synthetic processes. When a cell dies, chromatin forms coarse clumps inside the nucleus (pycnosis), and the nucleus itself breaks into pieces or even dissolves (karyorrhexis).
In damaged cells, mitotic activity is sharply reduced, cells are delayed at different stages of mitosis. The permeability of cell membranes is disturbed, as a result, vacuolization of the membrane organelles of the cell occurs. At the same time, there is an intensive accumulation in the cell of some individual products of disturbed metabolism. In general pathology, such changes in the structure of cells are called dystrophies. So, for example, with fatty degeneration, fat inclusions accumulate in the cells, with carbohydrate - glycogen, with protein - the deposition of protein granules, pigments, etc. The final stage of irreversible changes in cells is their death, at the level of tissue and organ this manifests itself in the form necrosis, or tissue (organ) death.
A special form of violations of the regulation of cell metabolism is a violation of cell differentiation, which most often leads to the development tumor process. Tumor cells are characterized by uncontrolled reproduction, autonomy of behavior in the body and violation of intercellular interactions. All these properties of tumor cells are preserved from generation to generation, i.e. are inherited. In connection with these features, cancer cells are considered mutants in terms of non-subordination of their behavior to the regulatory influences of the body.
Here an important role is played by the molecular processes of maintenance and regulation of ionic homeostasis of cells in normal conditions and during malignant transformation. concept ion homeostasis of the cell(IGK) includes a system for regulating the activity of ions that provide a normal intracellular environment, and water. Among the most important ions for cell life are K +, Na +, Ca 2+, H +, PO 2-, and ions of such energy-intensive molecules as ATP and ADP (adenosine diphosphate). IHC can control the behavior of the cell, primarily by changing the quantitative relationships between the main systems of the cell - for example, the intensity of protein and RNA synthesis, the mass of the cytoplasm and nucleus, etc. In the event of disruption of the work of IGK in cells, first of all, the molecular mechanisms of their interactions with each other change, as a result of which tumor cells acquire autonomy of behavior and low sensitivity to regulatory influences (Malenkov A.G., 1976).
Cell death.
There are two types of cell death – necrosis and apoptosis.
Necrosis It is caused mainly by various external factors that directly or indirectly affect membrane permeability and cell metabolism. In all cases, a chain of morphological and functional disorders occurs, eventually leading to cell dissolution - lysis.
So, necrosis is a form of cell death characterized by:
functionally - irreversible termination of their vital activity,
morphologically - violation of the integrity of membranes, changes in the nucleus (pycnosis, karyorrhexis, lysis), cytoplasm (edema), cell destruction, inflammatory reaction,
biochemically - a violation of energy production, coagulation and hydrolytic cleavage of proteins, nucleic acids, lipids,
genetically - the loss of genetic information. (Lushnikov E.F., Abrosimov A.Yu., 2001).
apoptosis- This is a process of cell death, which can occur without a primary violation of cellular metabolism. Apoptosis is more often called programmed cell death; This refers to the fact that this form of cell death actually develops according to the program laid down in the genetic apparatus of cells. At the same time, as a result of the action on the cell of various stimuli, certain genes are activated in the nucleus, stimulating the self-destruction of the cell. The self-destruction program can be implemented under the influence of some signal molecules of the organism itself - for example, hormones or protein molecules. So, lymphocytes multiplying in huge quantities in the thymus gland (thymus) almost all die within a few hours without leaving the thymus gland and in the bloodstream under the action of glucocorticoids - hormones of the adrenal cortex. The meaning of this phenomenon is completely unclear, but nevertheless it occurs exactly along the path of apoptosis.
The termination of some regulatory signal can lead to the activation of self-destruction genes. For example, after the removal of the testes, the cells of the prostate gland in men completely die.
Cell death, as if for no apparent reason, is common in the normal embryonic development of the organism. For example, tadpole tail cells die as a result of the activation of thyroid hormones at a certain stage of tadpole development. In an adult organism, mammary gland cells undergo apoptosis during its involution (reverse development).
Fig. Stages of development of apoptosis. The photo on the left is a normal cell;
In the center - the beginning of the fragmentation of the cytoplasm; on the right - the final stage
fragmentation of the cytoplasm and nucleus.
The process of apoptosis differs significantly from necrosis. This form of cell death is characterized by:
functionally - irreversible cessation of cell activity,
morphologically - loss of microvilli and intercellular contacts, condensation of chromatin and cytoplasm, shrinkage of cells, formation of vesicles from plasma membranes, fragmentation of cells and formation of micronuclei,
biochemically - hydrolysis of cytoplasmic proteins and DNA decay,
genetically - structural and functional restructuring of the genetic apparatus, culminating in the absorption of cell fragments by macrophages of tissues without an inflammatory reaction. (Lushnikov E.F., Abrosimov A.Yu., 2001).
The essence of apoptosis, its place in normal and pathological conditions.
In a multicellular organism, cell death occurs constantly, but in different tissues and organs it is observed under certain conditions. The biological essence of cell death is ambiguous. The most important and significant thing is that apoptosis has different meanings for the normal life of vertebrates and invertebrates (and now it has become known that for the plant world):
in embryogenesis, apoptosis is an element of development and is associated with the formation of tissues and organs,
with the independent existence of the organism, apoptosis is an integral part of metamorphosis (in insects and amphibians),
in animals, the processes of histogenesis and organogenesis proceed with the participation of apoptosis,
in a mature organism, apoptosis is part of the homeostatic mechanism of cell turnover,
during aging, apoptosis reflects the natural death of cells.
Reproductive cell death.
In connection with the stages of the cell cycle, there are two forms of cell death from external influences. One of them is reproductive death, which affects only dividing populations of cells. This form of cell death was discovered in radiobiological experiments on laboratory animals in the 1970s.
In irradiated animals, cytological studies revealed the loss of some cells of the ability to divide after passing through several cell cycles, followed by death. Moreover, this form of death is also observed in cells in in vitro culture.
Interphase cell death.
Another phenomenon, also discovered in radiobiological studies, is the immediate death of cells after irradiation, without division - in the interphase. This form of cell damage is typical for radiation effects in the hematopoietic system in the bone marrow, in the immune and nervous systems. According to modern concepts, interphase cell death occurs via apoptosis.
Lecture 7. General embryology. Basic concepts and phenomena.
Embryology(from the Greek.embryon - embryo) - the science of the laws of development of embryos. Medical embryology (E) studies the patterns of development of the human embryo, the causes of deformities and other deviations from the norm, possible ways and methods of influencing embryogenesis (the process of embryo formation).
At present, medical technologies make it possible in many cases to fight infertility, to carry out the birth of “test-tube” children, and to carry out transplantation of embryonic organs and tissues. Methods have already been developed for in vitro cultivation of eggs, in vitro fertilization, and implantation of the embryo into the uterus.
The process of human embryonic development has undergone a long evolution and largely reflects the stages of development of other representatives of the animal world. Therefore, the early stages of development of the human embryo are similar to similar stages in the embryogenesis of less organized chordates.
The human reproductive system includes several interrelated stages in the development of male and female germ cells, the fusion of these cells during fertilization and the formation of a new organism from the embryo. These steps are:
Progenesis - development and maturation of germ cells-eggs and spermatozoa. As a result of progenesis, a haploid (single) set of chromosomes appears in mature germ cells, structures are formed that contribute to their mutual fusion (fertilization) and the development of a new organism.
Embryogenesis- part of human ontogenesis (his individual development), includes the main stages: 1 - fertilization with the formation of a zygote, 2 - crushing of the zygote and the formation of a blastula (blastocyst), 3 - gastrulation - the formation of germ layers and a complex of axial organs, 4 - the formation of embryonic and extraembryonic tissues and organs,5- formation of organ systems (systemogenesis).
Post-embryonic period - the functioning of the new individual after birth outside the mother's body, including the continuation of the formation of organs and tissues after birth.
Progenesis.
Sex cells (gametes), unlike somatic cells, do not contain a double, but a single set of chromosomes. In humans, this double set is 46 chromosomes, therefore, gametes contain 23 chromosomes.
fig.Diploid chromosome set (46 chromosomes) in human somatic cells
All chromosomes in gametes are called autosomes- there are 22 of them in the gamete , with the exception of one - the twenty-third, which is called sex chromosome. AT male sex cells, half of the gametes (spermatozoa) ( FROM) contains a sex chromosome with female genetic material (X-chromosome), and half - a chromosome with male genetic material - Y-chromosome. In female gametes ) (I) All sex chromosomes are X-bearing. A characteristic feature of gametes is their low metabolic rate. In addition, mature gametes lose their ability to divide.
Male sex cells - spermatozoa - are formed in large quantities in most higher animals. In mammals and humans, spermatozoa are formed and mature during the entire active sexual period in the generative organs - the testicles, from the primary germ cells of the spermatogenic epithelium of the convoluted tubules. In the process of mitotic division, part of the spermatogonia (the next stage of differentiation of primary germ cells) enters the process of differentiation to the state of mature spermatozoa, and part does not differentiate and continues to divide mitotically, thereby maintaining the pool of stem (original) cells. (Next, meiosis should be briefly described. )
