Assimilation and dissimilation are opposite metabolic processes. Give a comparative description of the processes of assimilation and dissimilation in the cell and show their relationship
Metabolism and its types
It ensures the constancy of the internal environment of the body in changing conditions of existence - homeostasis . Metabolism consists of two interconnected and mutually opposite processes. These are processes dissimilation , in which splitting occurs organic matter and the released energy is used for the synthesis of ATP molecules, and the processes assimilation, in which ATP energy is used to synthesize the body’s own compounds necessary.
Dissimilation processes are also called catabolism and energy metabolism . And the processes of assimilation are also called anabolism and plastic metabolism . Such an abundance of synonyms for the same concept arose because metabolic reactions were studied by scientists of various specialties:
- biochemists,
- physiologists,
- cytology,
- genetics,
- molecular biologists.
But all the names and terms have taken root and are actively used by scientists.
Forms of energy supply to living organisms
For all living organisms on Earth, the Sun is the main source of energy. It is thanks to it that organisms satisfy their energy needs.
Organisms that can synthesize organic compounds from inorganic ones are called autotrophs. They are divided into two groups. Some are able to use the energy of sunlight. These are photosynthetics or phototrophs. These are mainly green plants, cyanobacteria (blue-green algae).
Another group of autotrophs uses energy that is released during chemical reactions. Such organisms are called chemotrophs or chemosynthetics.
Mushrooms, most of animals and bacteria cannot synthesize organic substances themselves. Such organisms are called heterotrophs. For them, the source of energy is organic compounds synthesized by autotrophs. Energy is used by living organisms for chemical, mechanical, thermal and electrical processes.
Preparatory stage of energy metabolism
Energy metabolism is conventionally divided into three main stages. The first stage was called preparatory. At this stage, macromolecules under the influence of enzymes are broken down into monomers. During the reactions, a fairly small amount of energy is released, which is dissipated in the form of heat.
Oxygen-free stage of energy metabolism
The oxygen-free (anaerobic) stage of energy metabolism occurs in cells. Monomers that were formed at the previous stage (glucose, glycerol, etc.) undergo further multi-stage breakdown without access to oxygen. The main thing at this stage is the process of splitting a glucose molecule into molecules of pyruvic or lactic acid with the formation of two molecules of ATP.
$C_6H_(12)O_6 + 2H_3PO_4 + 2ADP → 2C_3H_6O_3 + 2ATP + 2H_2O$
During this reaction (glycolysis reaction), about $200$ kJ of energy is released. However, not all of it turns into heat. Part of it is used for the synthesis of two energy-rich (macroergic) phosphate bonds in ATP molecules. Glucose is also broken down during alcoholic fermentation.
$C_6H_(12)O_6 + 2H_3PO_4 + 2ADP → 2C_2H_5OH + 2CO_2 + 2ATP + 2H_2O$
In addition to alcoholic fermentation, there are also such types of oxygen-free fermentation as butyric acid and lactic acid.
Oxygen stage of energy metabolism
At this stage, the compounds formed in the oxygen-free stage are oxidized to final products reactions - carbon dioxide and water. English biochemist Adolph Krebs discovered the sequence of transformations in 1937 organic acids in the mitochondrial matrix. In his honor, the set of these reactions was called the Krebs cycle.
Note 1
Complete oxidation of lactic or pyruvic acid molecules formed during the anaerobic process to carbon dioxide and water is accompanied by the release of $2800$ kJ of energy. This amount is enough to synthesize $36$ ATP molecules ($18$ times more than at the previous stage).
The overall equation for the oxygen stage of energy metabolism looks like this:
$2C_3H_6O_3 + 6O_2 + 36ADP + 36H_3PO_4 → 6CO_2 + 42H_2O + 36ATP$
To summarize, we can write the overall equation of energy metabolism:
$C_6H_(12)O_6 + 6O_2 + 38ADP + 38H_3PO_4 → 6CO_2 + 44H_2O + 38ATP$
At the final stage, metabolic products are removed from the body.
LESSON PLAN
Subject: Assimilation and dissimilation. Metabolism.
Full name Muratova Gulnaz Raushanovna
Place of work MBOU "Nizhnebishevskaya Secondary School"
Position: biology teacher
Subject biology
6. Basic textbook Biology. Introduction to general biology and ecology. 9th grade: educational. for educational institutions / A.A. Kamensky, E.A. Kriksunov, V.V. Beekeeper. - 11th ed., stereotype. - M.: Bustard, 2010
The purpose of the lesson:
Introduce students to the concept of “metabolism in the body”, assimilation, dissimilation, metabolism.
Lesson objectives:
Educational: to concretize knowledge about metabolism (metabolism) as a property of living organisms, to introduce the two sides of exchange, to identify general patterns metabolism; establish a connection between plastic and energy metabolism on different levels organizations of living things and their connection with environment.
Developmental: to develop the ability to highlight the essence of the process in the material being studied; generalize and compare, draw conclusions; work with text, diagrams, and other sources;
realization of students' creative potential, development of independence.
Educational: using acquired knowledge, understand perspectives practical use photosynthesis; understand the influence of metabolism on maintaining and promoting health.
Equipment: computer, projector, presentation.
Lesson type: learning new material.
Forms of student work: independent work with the textbook, individual work at the board, front work.
During the classes
Organizing time.
II. Repetition of material
Checking the correctness of filling out the table “Comparison of the structure of eukaryotic and prokaryotic cells.” (Student's answer at the board.)
Frontal conversation on the following issues:
What role does the spore play in prokaryotes? How is it different from eukaryotic spores?
Comparing the structure and vital processes of eukaryotes and prokaryotes, highlight features that allow you to assume which cells are historically more ancient and which are younger.
What are enzymes? What is their role in the body?
What is metabolism? Give examples of metabolism in the body.
III. Learning new material.
Assignment: compare two definitions, find whether they are different or similar. How can you explain this?
Metabolism consists of two interrelated processes - anabolism and catabolism.
1. During assimilation, the biosynthesis of complex molecules occurs from simple precursor molecules or from molecules of substances coming from external environment.
2. The most important processes assimilation are protein synthesis and nucleic acids(common to all organisms) and carbohydrate synthesis (only in plants, some bacteria and cyanobacteria).
3. During the process of assimilation during the formation of complex molecules, energy is accumulated, mainly in the form of chemical bonds.
1. When chemical bonds in molecules of organic compounds are broken, energy is released and stored in the form of ATP.
2. ATP synthesis in eukaryotes occurs in mitochondria and chloroplasts, and in prokaryotes - in the cytoplasm, on membrane structures.
3. Dissimilation provides all biochemical processes in the cell with energy.
All living cells constantly need energy to carry out various biological and chemical reactions within them. Some organisms use the energy of sunlight (during photosynthesis) for these reactions, while others use the energy of chemical bonds of organic substances supplied with food. Energy is extracted from food substances in the cell by their breakdown and oxidation by oxygen supplied during respiration. Therefore this process is called biological oxidation , or cellular respiration .
Biological oxidation involving oxygen is called aerobic , without oxygen – anaerobic . The process of biological oxidation occurs in a multi-stage process. At the same time, energy accumulates in the cell in the form of ATP molecules and other organic compounds.
IV. Consolidation of the studied material.
What is assimilation? Give examples of synthesis reactions in a cell.
What is dissimilation? Give examples of decay reactions in a cell.
Prove that assimilation and dissimilation are two sides of a single process of metabolism and energy - metabolism.
Exercise. Establish a correspondence between the processes occurring in the cells of organisms and their belonging to assimilation or dissimilation:
| Processes occurring in cells | Metabolism |
|
| 1. Water evaporation 2. Breathing 3. Breakdown of fats 4. Protein biosynthesis 5. Photosynthesis 6. Protein breakdown | 7.Cleavage 8. Biosynthesis of fats 9.Synthesis 10. Chemosynthesis | A – assimilation B – dissimilation |
Answer: 1 – B, 2 – B, 3 – B, 4 – A, 5 – A, 6 – B, 7 – B, 8 – A, 9 – A, 10 – A.
Homework: Study § 2.8 “Assimilation and dissimilation. Metabolism”, answer the questions at the end of the paragraph, repeat § 1.7.
Nutrient Value
In all living organisms today, from the most primitive to the most complex - human body, - metabolism and energy are the basis of life.
In the human body, in its organs, tissues, cells, there is a continuous process of creation and formation of complex substances. At the same time, decay and destruction of complex organic substances that make up the cells of the body occur.
The work of organs is accompanied by their continuous renewal: some cells die, others replace them. In an adult, 1/20 of the skin epithelium, half of all epithelial cells of the digestive tract, about 25 g of blood, etc. die and are replaced within 24 hours.
Growth and renewal of body cells are possible only if oxygen and nutrients are continuously supplied to the body. Nutrients are the building blocks plastic the material from which living things are built.
For the construction of new body cells, their continuous renewal, for the functioning of organs such as the heart, gastrointestinal tract, breathing apparatus, kidneys, etc., as well as for a person to perform work, energy is needed. The body receives this energy from the breakdown of cell substances during metabolism.
Thus, the nutrients entering the body serve not only as plastic, building material, but also a source of energy so necessary for life.
Under metabolism understand the totality of changes that substances undergo from the moment they enter the digestive tract until the formation of final breakdown products excreted from the body.
Assimilation and dissimilation
Metabolism is the unity of two processes: assimilation and dissimilation. As a result of the process assimilation relatively simple products digestion, entering the cells, undergo chemical transformations with the participation of enzymes and become similar necessary for the body substances. Dissimilation- the breakdown of complex organic substances that make up the cells of the body. Some of the breakdown products are reused by the body, and some are excreted from the body.
The dissimilation process also occurs with the participation of enzymes. During dissimilation, energy is released. It is due to this energy that new cells are built, old ones are renewed, the human heart functions, and mental and physical work is performed.
The processes of assimilation and dissimilation are inseparable from each other. When the process of assimilation intensifies, especially during the growth of a young organism, the process of dissimilation also intensifies.
Transformation of substances
Chemical transformations of food substances begin in digestive tract. Here complex proteins, fats and carbohydrates are broken down into simpler ones that can be absorbed through the intestinal mucosa and become building material during the assimilation process. Digestion releases a small amount of energy in the digestive tract. Substances received as a result of absorption into the blood and lymph are brought into the cells, where they undergo major changes. The resulting complex organic substances are part of the cells and take part in the implementation of their functions. The energy released during the breakdown of cell substances is used for the life of the body. Metabolic products not used by the body various organs and tissues are released from it.
The role of enzymes in intracellular metabolism
The main processes of transformation of substances take place inside the cells of our body. These processes underlie intracellular exchange. Decisive role in intracellular metabolism belongs to numerous cell enzymes. Thanks to their activity, complex transformations occur with cell substances, intramolecular chemical bonds in them are broken, which leads to the release of energy. Oxidation and reduction reactions are of particular importance here. The end products of oxidation processes in the cell are carbon dioxide and water. With the participation of special enzymes, other types of chemical reactions in the cell are carried out.
The energy released during these reactions is used to build new substances in the cell and to maintain the vital processes of the body. The main battery and carrier of energy used in many synthetic processes is adenosine triphosphoric acid (ATP). The ATP molecule contains three phosphoric acid residues. ATP is used in all metabolic reactions that require energy. In the ATP molecule, the chemical bond with one or two phosphoric acid residues is broken, releasing stored energy (the cleavage of one phosphoric acid residue results in the release of about 42,000 J per 1 gram molecule).
Nutrients entering the body undergo complex changes and are converted into substances of the body itself and its tissues. The processes of formation from simple compounds (entered into the body from the digestive apparatus) into complex ones, as well as the processes of growth and creation of new cells and tissues are called plastic processes, and absorption by the body nutrients called assimilation . By assimilating nutrients, the body receives with them a supply of hidden energy.
This energy can serve as a source of tissue vital activity. For example, muscle contraction occurs due to the latent energy received muscle tissue together with assimilated substances, and depends on the transformation of latent energy into mechanical energy; An increase in muscle temperature occurs from the conversion of latent energy into heat.
At the same time, in the body, in connection with its work, substances are broken down, their partial destruction occurs, as a result of which complex substances disintegrate and are oxidized to simpler ones. The process of decay and destruction of body substances is called dissimilation . In the process of dissimilation, latent energy is converted into effective, mainly mechanical and thermal. At the same time, glycogen and other substances break down in the muscles and metabolic products (lactic, phosphoric acid, etc.) are formed. Subject to final oxidation, these metabolic products are converted into carbon dioxide and water and excreted by the body.
Some of the metabolic products can be reused by the body. Assimilation processes lead to the accumulation of substances, increasing them in the body; processes of dissimilation lead to a decrease and waste of reserves of substances and energy.
The processes of assimilation and dissimilation involve various enzymes. Almost all biological processes occurring in the body are in one way or another connected with their activities. Each enzyme activates only certain chemical reactions. The enzymes themselves are also formed as a result of cell activity and, consequently, metabolism.
Violation of enzyme activity entails severe consequences for the body, up to its death due to metabolic disorders.
Assimilation and dissimilation are two opposing processes, but both of them are inextricably linked with each other. If assimilation processes stopped in the body, then after some time dissimilation would lead to complete exhaustion and destruction of tissues.
The entire set of processes of transformation of substances occurring in the body, including the processes of assimilation and dissimilation, is called metabolism.
The cell as a structural and functional unit living represents open system, i.e. constantly exchanges matter and energy with the environment.
Cellular metabolism refers to the continuous supply of substances into the cell from the external environment, the chemical transformation of these substances and the release of the final products of chemical reactions.
Functions of cellular metabolism:
1. Providing the cell with the building material necessary for the formation of cellular structures;
2. Supplying the cell with energy, which is used for vital processes (synthesis of substances, transport of substances, etc.);
3. Maintaining relative constancy of composition and physical and chemical properties cells;
4. Self-renewal of cells and tissues.
Distinguish external exchange – absorption and release of substances, and internal exchange– chemical transformation of these substances in the cell.
Internal exchange, or metabolism, is a combination of two opposite reactions: anabolic and catabolic.
Anabolic reactions- These are reactions of synthesis of complex organic substances from simpler ones. They occur with the expenditure of energy, ensuring the constancy of the composition of the cells and tissues of the body. The set of these reactions is called assimilation or plastic exchange. An example of assimilation would be protein biosynthesis, the synthesis of carbohydrates from water and carbon dioxide during photosynthesis, the synthesis of nucleotides, DNA, RNA, polysaccharides, lipids and other compounds.
Catabolic reactions- these are reactions of the breakdown of complex organic substances (fats, proteins and carbohydrates) into simpler ones with the release of energy, a significant part of which goes to the formation of ATP. These reactions are often called energy metabolism, or dissimilation.
The set of reactions of assimilation and dissimilation form the basis of the vital activity of the cell, and, consequently, of the tissue, organ and organism as a whole.
| energetic |
| ATP-consumed |
| ATP is formed |
| ATP (ADENOSINE TRIPHOSPHATE) |
Rice. 5.1. Metabolism and ATP in the cell
ATP + H 2 O ↔ ADP + H 3 PO 4 + 40 kJ
The processes of assimilation are not always in accordance with the processes of dissimilation. During the period of intensive growth and development of the organism, assimilation processes predominate. On the contrary, with aging, intense physical work, and lack of nutrients, the processes of dissimilation prevail over the processes of assimilation.
Distinguish autotrophic And heterotrophic assimilation. In heterotrophic assimilation (animals, fungi), food substances (chemical energy) serve as the source of energy; in autotrophic assimilation, light energy used for photosynthesis (Fig. 5.2.)
Fig.5.2. Metabolism of substances and energy in autotrophic and heterotrophic cells
From Fig. 5.2. It is clear that the existence of life on Earth depends on the energy of the Sun and its complex transformations in auto- and heterotrophic cells of organisms. In a simplified form, the flow of energy in living nature can be represented as follows:
1. Solar energy → autotrophs → organic substances → ATP → various shapes work.
2. Solar energy → autotrophs → organic substances → heterotrophs → ATP → various forms of work
Autotrophs– synthesize organic substances from inorganic ones.
Heterotrophs– consume ready-made organic substances synthesized by other organisms.
Flow of energy in a cell
The flow of energy in a cell is based on the processes of nutrition of organisms and cellular respiration.
1. Food– the process of acquiring matter and energy by living organisms.
2. Cellular respiration- the process by which living organisms release energy from organic substances rich in it when they are enzymatically broken down (dissimilated) into simpler ones. Cellular respiration can be aerobic or anaerobic.
3. Aerobic respiration– energy is obtained with the participation of oxygen in the process of breakdown of organic substances. It is also called the oxygen (aerobic) stage of energy metabolism.
Anaerobic respiration– obtaining energy from food without using free atmospheric oxygen. IN general view The flow of energy in a cell can be represented as follows (Figure 5.3.)
| FOOD |
| SUGAR, FATTY ACIDS, AMINO ACIDS |
| CELLULAR RESPIRATION |
| ATP |
| CO 2, H 2 O, NH 3 |
| CHEMICAL, MECHANICAL, ELECTRICAL, OSMOTIC WORK |
| ADP + H 3 PO 4 |
Fig.5.3. Flow of energy in a cell
Chemical work : biosynthesis in the cell of proteins, nucleic acids, fats, polysaccharides.
Mechanical work : reduction muscle fibers, beating of cilia, segregation of chromosomes during mitosis.
Electrical work– maintaining a potential difference across the cell membrane.
Osmotic work– maintenance of substance gradients in the cell and its environment.