Difference between photosynthesis and chemosynthesis. Chemosynthesis is a unique process of feeding bacteria. How does chemosynthesis differ from photosynthesis?

All living things need food and nutrients. When feeding, they use energy stored primarily in organic compounds - proteins, fats, carbohydrates. Heterotrophic organisms use food of plant and animal origin that already contains organic compounds. Plants create organic matter through the process of photosynthesis.

Research into photosynthesis began in 1630 with the experiments of the Dutchman van Helmont. He proved that plants do not obtain organic matter from the soil, but create it themselves.

Joseph Priestley in 1771 proved the “correction” of air with plants. Placed under a glass cover, they absorbed carbon dioxide released by the smoldering splinter.

It has now been established that photosynthesis is the process of formation of organic compounds from CO 2 and water using light energy and takes place in the chloroplasts of green plants and the green pigments of some photosynthetic bacteria.

Chloroplasts and folds of the cytoplasmic membrane of prokaryotes contain a green pigment - chlorophyll, a molecule of which is capable of being excited by sunlight, donating its electrons and moving them to higher energy levels. This process can be compared to throwing a ball up. As the ball rises, it stores potential energy; falling, he loses her. The electrons do not fall back, but are picked up by electron carriers (NADP+ - nicotinamide diphosphate). In this case, the energy they previously accumulated is partially spent on the formation of ATP. Continuing the comparison with a thrown ball, we can say that the ball, as it falls, heats the surrounding space, and part of the energy of the falling electrons is stored in the form of ATP. The process of photosynthesis is divided into reactions caused by light and reactions associated with carbon fixation: light And dark phases.

Light phase- This is the stage at which the light energy absorbed by chlorophyll is converted into electrochemical energy in the electron transport chain. It is carried out in the light, in gran membranes with the participation of transporter proteins and ATP synthetase.

Reactions, caused by light, occur on the photosynthetic membranes of the chloroplast granules:

1) excitation of chlorophyll electrons by light quanta and their transition to a higher energy level;

2) reduction of electron acceptors – NADP+ to NADP H

2H+ + 4e- + NADP+ → NADP H;

3) photolysis of water: 2H 2 O → 4H+ + 4e- + O 2.

This process takes place inside thylakoids– folds of the inner membrane of chloroplasts from which they are formed grains– stacks of membranes.

results light reactions:

photolysis of water with the formation of free oxygen,

ATP synthesis,

reduction of NADP+ to NADP N.

Dark phase– the process of converting CO 2 into glucose into stroma(space between grana) of chloroplasts using the energy of ATP and NADP H.

Result dark reactions: the conversion of carbon dioxide into glucose and then into starch. In addition to glucose molecules, the formation of amino acids, nucleotides, and alcohols occurs in the stroma.

The overall equation for photosynthesis is -

The meaning of photosynthesis:

free oxygen is formed, which is necessary for the respiration of organisms and the formation of a protective ozone screen (protecting organisms from the harmful effects of ultraviolet radiation);

production of raw organic substances - food for all living beings;

reducing the concentration of carbon dioxide in the atmosphere.

Chemosynthesis – the formation of organic compounds from inorganic ones due to the energy of redox reactions of nitrogen, iron, and sulfur compounds.

The role of chemosynthesis: chemosynthetic bacteria destroy rocks, purify wastewater, and participate in the formation of minerals.

Thematic assignments

A1. Photosynthesis is associated with:

1) the breakdown of organic substances into inorganic ones

2) the creation of organic substances from inorganic

3) chemical conversion of glucose into starch

4) formation of cellulose

A2. The starting material for photosynthesis is

1) proteins and carbohydrates

2) carbon dioxide and water

3) oxygen and ATP

4) glucose and oxygen

A3. The light phase of photosynthesis occurs

1) in grana of chloroplasts

2) in leukoplasts

3) in the stroma of chloroplasts

4) in mitochondria

A4. The energy of excited electrons in the light stage is used for:

1) ATP synthesis

2) glucose synthesis

3) protein synthesis

4) breakdown of carbohydrates

A5. As a result of photosynthesis, chloroplasts produce:

1) carbon dioxide and oxygen

2) glucose, ATP and oxygen

3) proteins, fats, carbohydrates

4) carbon dioxide, ATP and water

A6. Chemotrophic organisms include

1) pathogens of tuberculosis

2) lactic acid bacteria

3) sulfur bacteria

IN 1. Select the processes occurring in the light phase of photosynthesis

1) photolysis of water

2) glucose formation

3) synthesis of ATP and NADP H

4) use of CO 2

5) education O 2

6) use of ATP energy

AT 2. Select the substances involved in the process of photosynthesis

1) cellulose

2) glycogen

3) chlorophyll

6) nucleic acids

Chemosynthesis (from chemo... and synthesis), or more correctly, chemolithoautotrophy, is a type of nutrition characteristic of some bacteria that are capable of assimilating CO 2 as the only source of carbon due to the energy of oxidation of inorganic compounds. The discovery of chemosynthesis in 1887 (S. N. Vinogradsky) significantly changed ideas about the main types of metabolism in living organisms. Unlike photosynthesis, chemosynthesis does not use light energy, but the energy obtained from redox reactions, which must be sufficient for the synthesis of adenosine triphosphoric acid (ATP) and exceed 10 kcal/mol.

Bacteria capable of chemosynthesis are not a single taxonomic group, but are systematized depending on the oxidized inorganic substrate. Among them there are microorganisms that oxidize hydrogen, carbon monoxide, reduced sulfur compounds, iron, ammonia, nitrites, and antimony.

Hydrogen bacteria are the most numerous and diverse group of chemosynthetic organisms; carry out the reaction 6H 2 + 2O 2 + CO 2 = (CH 2 O) + 5H 2 O, where (CH 2 O) is the symbol for the resulting organic substances. Compared to other autotrophic microorganisms, they are characterized by a high growth rate and can produce large biomass. These bacteria are also capable of growing on media containing organic substances, i.e. they are mycotrophic, or facultatively chemoautotrophic bacteria.

Close to hydrogen bacteria are carboxydobacteria, which oxidize CO using the reaction 25CO + 12O 2 + H 2 O + 24CO 2 + (CH 2 O). Thionic bacteria oxidize hydrogen sulfide, thiosulfate, and molecular sulfur to sulfuric acid. Some of them (Thiobacillus ferrooxidans) oxidize sulfide minerals, as well as ferrous iron. The ability for chemosynthesis in various aquatic sulfur bacteria remains unproven.

Nitrifying bacteria oxidize ammonia to nitrite (1st stage of nitrification) and nitrite to nitrate (2nd stage). Under anaerobic conditions, chemosynthesis is observed in some denitrifying bacteria that oxidize hydrogen or sulfur, but they often require organic matter for biosynthesis (lithoheterotrophy). Chemosynthesis has been described in some strictly anaerobic methane-producing bacteria according to the reaction 4H 2 + CO 2 = CH 4 + 2H 2 O.

The biosynthesis of organic compounds during chemosynthesis occurs as a result of autotrophic assimilation of CO 2 (Calvin cycle) in the same way as during photosynthesis. Energy in the form of ATP is obtained from the transfer of electrons through a chain of respiratory enzymes embedded in the bacterial cell membrane. Some oxidizable substances donate electrons to the chain at the level of cytochrome c, which creates additional energy consumption for the synthesis of the reducing agent. Due to the high energy consumption, chemosynthesizing bacteria, with the exception of hydrogen ones, form little biomass, but oxidize a large amount of inorganic substances.

In the biosphere, chemosynthetic bacteria control the oxidative sites of the cycle of the most important elements and therefore are of exceptional importance for biogeochemistry. Hydrogen bacteria can be used to produce protein and purify the atmosphere from CO 2 in closed ecological systems. Morphologically, chemosynthetic bacteria are very diverse, although most of them belong to pseudomonads; they are found among budding and filamentous bacteria, spirilla, leptospira, and corynebacteria.

Green plants (autotrophs) are the basis of life on the planet. Almost all food chains begin with plants. They convert the energy that falls on them in the form of sunlight into energy stored in carbohydrates, the most important of which is the six-carbon sugar glucose. This energy conversion process is called photosynthesis. The overall equation for photosynthesis looks like this:

water + carbon dioxide + light > carbohydrates + oxygen

In 1905, English plant physiologist Frederick Blackman conducted research and established the basic processes of photosynthesis. Blackman concluded that two processes were occurring: one was highly dependent on light level but not temperature, while the other was strongly influenced by temperature regardless of light level. This insight formed the basis of modern ideas about photosynthesis. The two processes are sometimes called “light” and “dark” reactions, which is not entirely correct, since it turned out that although the reactions of the “dark” phase occur in the absence of light, they require products of the “light” phase.

Photosynthesis begins when photons emitted by the sun enter special pigment molecules found in the leaf - chlorophyll molecules. Chlorophyll is found in leaf cells, in the membranes of cellular organelles of chloroplasts (they are the ones that give the leaf its green color). The process of energy capture consists of two stages and is carried out in separate clusters of molecules - these clusters are usually called Photosystem I and Photosystem II. The cluster numbers reflect the order in which these processes were discovered, and this is one of the funny scientific oddities, since in the leaf the reactions in Photosystem II occur first, and only then in Photosystem I.

When a photon collides with 250-400 molecules of Photosystem II, the energy increases abruptly and is transferred to the chlorophyll molecule. At this point, two chemical reactions occur: the chlorophyll molecule loses two electrons (which are accepted by another molecule, called an electron acceptor) and the water molecule splits. The electrons of the two hydrogen atoms that were part of the water molecule replace the two electrons lost by chlorophyll.

After this, the high-energy (“fast”) electron is transferred to each other like a hot potato by the molecular carriers assembled in a chain. In this case, part of the energy goes to the formation of the adenosine triphosphate (ATP) molecule, one of the main energy carriers in the cell. Meanwhile, a slightly different Photosystem I chlorophyll molecule absorbs the energy of the photon and donates an electron to another acceptor molecule. This electron is replaced in chlorophyll by an electron that arrived along the chain of carriers from Photosystem II. The energy of the electron from Photosystem I and the hydrogen ions previously formed during the splitting of a water molecule are used to form NADP-H, another carrier molecule.

As a result of the process of light capture, the energy of two photons is stored in the molecules used by the cell to carry out reactions, and an additional oxygen molecule is formed. After solar energy is absorbed and stored, it is the turn of carbohydrates to be formed. The basic mechanism of carbohydrate synthesis in plants was discovered by Melvin Calvin. The cycle of converting solar energy into carbohydrates consists of a series of chemical reactions that begin with the combination of an incoming molecule with a “helper” molecule, followed by the initiation of other chemical reactions. These reactions lead to the formation of the final product and at the same time reproduce the “helper” molecule, and the cycle begins again. In the Calvin cycle, the role of such a “helper” molecule is played by the five-carbon sugar ribulose diphosphate (RDP). The Calvin cycle begins with carbon dioxide molecules combining with RDP. Due to the energy of sunlight stored in the form of ATP and NADP-H, chemical reactions of carbon fixation first occur to form carbohydrates, and then reactions of the reconstruction of ribulose diphosphate occur. During the six turns of the cycle, six carbon atoms are incorporated into the molecules of the precursors of glucose and other carbohydrates. This cycle of chemical reactions will continue as long as energy is supplied. Thanks to this cycle, the energy of sunlight becomes available to living organisms.

27-Feb-2014 | One Comment | Lolita Okolnova

Photosynthesis- the process of formation of organic substances from carbon dioxide and water in the light with the participation of photosynthetic pigments.

Chemosynthesis- a method of autotrophic nutrition in which the source of energy for the synthesis of organic substances from CO 2 is the oxidation reactions of inorganic compounds

Typically, all organisms capable of synthesizing organic substances from inorganic substances, i.e. organisms capable of photosynthesis and chemosynthesis, refer to .

Some are traditionally classified as autotrophs.

We talked briefly about the structure of a plant cell, let's look at the whole process in more detail...

The essence of photosynthesis

(summary equation)

The main substance involved in the multi-stage process of photosynthesis is chlorophyll. It is this that transforms solar energy into chemical energy.

The figure shows a schematic representation of the chlorophyll molecule, by the way, the molecule is very similar to the hemoglobin molecule...

Chlorophyll is built into chloroplast grana:

Light phase of photosynthesis:

(carried out on thylakoid membranes)

• Light hitting a chlorophyll molecule is absorbed by it and brings it into an excited state - the electron that is part of the molecule, having absorbed the energy of light, moves to a higher energy level and participates in synthesis processes;
• Under the influence of light, splitting (photolysis) of water also occurs:

In this case, oxygen is removed into the external environment, and protons accumulate inside the thylakoid in the “proton reservoir”

2Н + + 2е - + NADP → NADPH 2

NADP is a specific substance, a coenzyme, i.e. a catalyst, in this case a hydrogen carrier.

• synthesized (energy)

Dark phase of photosynthesis

(occurs in the stroma of chloroplasts)

actual glucose synthesis

a cycle of reactions occurs in which C 6 H 12 O 6 is formed. These reactions use the energy of ATP and NADPH 2 formed in the light phase; In addition to glucose, other monomers of complex organic compounds are formed during photosynthesis - amino acids, glycerol and fatty acids, nucleotides

Please note: this phase is dark it is called not because it occurs at night - glucose synthesis occurs, in general, around the clock, but the dark phase no longer requires light energy.

“Photosynthesis is a process on which all manifestations of life on our planet ultimately depend.”

K.A. Timiryazev.

As a result of photosynthesis, about 150 billion tons of organic matter are formed on Earth and about 200 billion tons of free oxygen are released per year. In addition, plants involve billions of tons of nitrogen, phosphorus, sulfur, calcium, magnesium, potassium and other elements into the cycle. Although a green leaf uses only 1-2% of the light falling on it, the organic matter created by the plant and oxygen in general.

Chemosynthesis

Chemosynthesis is carried out due to the energy released during chemical oxidation reactions of various inorganic compounds: hydrogen, hydrogen sulfide, ammonia, iron (II) oxide, etc.

According to the substances included in the metabolism of bacteria, there are:

• sulfur bacteria - microorganisms of water bodies containing H 2 S - sources with a very characteristic odor,
• iron bacteria,
• nitrifying bacteria - oxidize ammonia and nitrous acid,
• nitrogen-fixing bacteria - enrich soils, greatly increase productivity,
• hydrogen-oxidizing bacteria

But the essence remains the same - this is also

Who among us does not remember the definition of “photosynthesis” from botany lessons at school? “The process of formation of organic matter from carbon dioxide and water in the light with the participation of photosynthetic pigments.” Knowing this laconic definition by heart, few of us wondered what it hides behind it?

Essentially, photosynthesis is a chemical reaction as a result of which six CO2 molecules combine with six water molecules to form one glucose molecule - the building block of our organic matter. Molecular oxygen produced during photosynthesis is just a by-product. However, this very “by-product” is one of the main sources of atmospheric oxygen, so necessary for higher organisms.

It would seem that everything is very simple: the cell of a photosynthetic organism is a kind of “cone” for the chemical reaction of two components. But in reality, the reaction mechanism turns out to be much more complex. It turns out that the process consists of two reactions: “light” and “dark”. The first is associated with the splitting of a water molecule into hydrogen and oxygen using light energy. Sunlight is absorbed by the cell's special light-absorbing pigment, chlorophyll (colored green). Next, the energy is transferred into ATP molecules, which release the resulting energy in the second stage of photosynthesis - the “dark” reaction. The "dark" reaction is the direct reaction between carbon dioxide and hydrogen to form glucose.

Photosynthesis can be carried out by plants, algae and some types of microorganisms. Thanks to their vital activity, it becomes possible for the existence, for example, of animals whose food consists of organic substances. But is photosynthesis the only form of converting carbon dioxide into organic matter? No. It turns out that nature also provides another, alternative, path for the formation of organic substances from CO2 - chemosynthesis.

The difference between chemosynthesis and photosynthesis is the absence of a “light” reaction. As a source of energy, the cells of chemosynthetic organisms do not use the energy of sunlight, but the energy of chemical reactions. Which ones? Reactions of oxidation of hydrogen, carbon monoxide, reduction of sulfur, iron, ammonia, nitrite, antimony.

Of course, each chemosynthetic organism uses its own chemical reaction as a source of energy. For example, hydrogen bacteria oxidize hydrogen, nitrifying bacteria convert ammonia into nitrate form, etc. However, they all store the energy released during a chemical reaction in the form of ATP molecules. Further, the process proceeds according to the type of reactions of the dark stage of photosynthesis.
Only some types of bacteria have the ability to chemosynthesize. Their role in nature is colossal. They do not “produce” atmospheric oxygen and do not accumulate large quantities of organic matter. However, the chemical reactions that they use in the course of their life play a key role in biogeochemistry, ensuring, among other things, the cycle of nitrogen, sulfur and other elements in nature.

Photosynthesis and chemosynthesis are some of the most fascinating processes that occur in living organisms. Knowing the differences between these two reactions is considered a necessary minimum for a high school student, but it is the comparison of these all-important processes that often drives the most diligent and thoughtful students into a stupor.

Definition

Photosynthesis- the process of synthesis of organic matter, stimulated by the energy of sunlight.

Chemosynthesis– the process of formation of organic compounds, which “starts up” without the mandatory presence of solar quanta.

Comparison

Photosynthesis is the source of vital activity of living autotrophic beings, namely the vast majority of representatives of the kingdom of Plants and some types of Bacteria, which in turn serve as the main food or the beginning of the food pyramid for heterotrophic and saprotrophic organisms. Thanks to photosynthesis, 150 billion tons of organic matter are formed annually on Earth, and the atmosphere is replenished with 200 billion tons of oxygen, suitable for respiration by other organisms.

Photosynthesis occurs in plastids - organelles of plant cells that have the pigment chlorophyll. In the process of the redox reaction, which is photosynthesis, the plant consumes water and inorganic substances, namely carbon dioxide. This process is stimulated by the presence of energy from solar quanta. As a result of the reaction, oxygen is released and organic substances are synthesized - in most cases glucose, also known as hexose or grape sugar.

Thanks to chemosynthesis, a nitrogen cycle occurs in the biosphere, sulfur bacteria weather rocks, creating the basis for the formation of soils, and hydrogen bacteria oxidize dangerous amounts of hydrogen that accumulate during the life of some microorganisms. In addition, nitrifying bacteria help increase soil fertility, and sulfur bacteria are involved in wastewater purification.

Chemosynthesis is located in the cells of bacteria and archaea. In the process of redox reactions, organic substances are synthesized. Not directly, but through the formation of ATP energy, which is later spent on the synthesis of organic matter. To do this, living organisms use CO 2, hydrogen and oxygen formed by the oxidation of ammonia, iron oxide, hydrogen sulfide and hydrogen. Considering that chemosynthesis can occur underground, in the depths of the World Ocean, in the middle of other living organisms, it is not tied to light energy, it is not “started up” by it, and it does not depend on the Sun.

Conclusions website

1. Photosynthesis is impossible without the energy of sunlight; chemosynthesis does not need it.
2. Plants and bacteria photosynthesize, bacteria and archaea chemosynthesize.
3. Both processes have different biological significance.