Photosynthesis occurs in the leaf of green plants. Photosynthesis. The meaning of photosynthesis. Light and Dark phases of photosynthesis. Two stages of photosynthesis
There are three types of plastids:
- chloroplasts- green, function - photosynthesis
- chromoplasts- red and yellow, are dilapidated chloroplasts, can give bright colors to petals and fruits.
- leucoplasts- colorless, function - storage of substances.
The structure of chloroplasts
Covered with two membranes. The outer membrane is smooth, the inner one has outgrowths inward - thylakoids. Stacks of short thylakoids are called grains, they increase the area of the inner membrane in order to accommodate as many photosynthetic enzymes as possible.
The internal environment of the chloroplast is called the stroma. It contains circular DNA and ribosomes, due to which chloroplasts independently make part of their proteins, which is why they are called semi-autonomous organelles. (It is believed that plastids were previously free bacteria that were absorbed by a large cell, but not digested.)
Photosynthesis (simple)
In the green leaves in the light
In chloroplasts using chlorophyll
From carbon dioxide and water
Glucose and oxygen are synthesized.
Photosynthesis (medium difficulty)
1. Light phase.
Occurs in the light in the grana of chloroplasts. Under the influence of light, decomposition (photolysis) of water occurs, producing oxygen, which is released, as well as hydrogen atoms (NADP-H) and ATP energy, which are used in the next stage.
2. Dark phase.
Occurs both in light and in darkness (light is not needed), in the stroma of chloroplasts. From carbon dioxide obtained from the environment and hydrogen atoms obtained in the previous stage, glucose is synthesized using the energy of ATP obtained in the previous stage.
Choose one, the most correct option. Cellular organelle containing a DNA molecule
1) ribosome
2) chloroplast
3) cell center
4) Golgi complex
Answer
Choose one, the most correct option. In the synthesis of what substance do hydrogen atoms participate in the dark phase of photosynthesis?
1) NADP-2H
2) glucose
3) ATP
4) water
Answer
Choose one, the most correct option. Which cellular organelle contains DNA?
1) vacuole
2) ribosome
3) chloroplast
4) lysosome
Answer
Choose one, the most correct option. In cells, primary glucose synthesis occurs in
1) mitochondria
2) endoplasmic reticulum
3) Golgi complex
4) chloroplasts
Answer
Choose one, the most correct option. Oxygen molecules during photosynthesis are formed due to the decomposition of molecules
1) carbon dioxide
2) glucose
3) ATP
4) water
Answer
Choose one, the most correct option. The process of photosynthesis should be considered as one of the important links in the carbon cycle in the biosphere, since during its
1) plants absorb carbon from inanimate nature into living matter
2) plants release oxygen into the atmosphere
3) organisms release carbon dioxide during respiration
4) industrial production replenish the atmosphere with carbon dioxide
Answer
Choose one, the most correct option. Are the following statements about photosynthesis correct? A) In the light phase, the energy of light is converted into the energy of chemical bonds of glucose. B) Dark phase reactions occur on thylakoid membranes, into which carbon dioxide molecules enter.
1) only A is correct
2) only B is correct
3) both judgments are correct
4) both judgments are incorrect
Answer
CHLOROPLAST
1. All of the following characteristics, except two, can be used to describe the structure and functions of the chloroplast. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) is a double-membrane organelle
2) has its own closed DNA molecule
3) is a semi-autonomous organelle
4) forms the spindle
5) filled with cell sap with sucrose
Answer
2. Select three features of the structure and functions of chloroplasts
1) internal membranes form cristae
2) many reactions occur in grains
3) glucose synthesis occurs in them
4) are the site of lipid synthesis
5) consist of two different particles
6) double-membrane organelles
Answer
3. Choose three correct answers out of six and write down the numbers under which they are indicated. The following processes occur in the chloroplasts of plant cells:
1) hydrolysis of polysaccharides
2) breakdown of pyruvic acid
3) photolysis of water
4) breakdown of fats into fatty acids and glycerol
5) synthesis of carbohydrates
6) ATP synthesis
Answer
CHLOROPLASTS EXCEPT
1. The following terms, except two, are used to describe plastids. Identify two terms that “drop out” from the general list and write down the numbers under which they are indicated in the table.
1) pigment
2) glycocalyx
3) grana
4) crista
5) thylakoid
Answer
2. All but two of the following characteristics can be used to describe chloroplasts. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) double-membrane organelles
2) use light energy to create organic substances
3) internal membranes form cristae
4) glucose synthesis occurs on the cristae membranes
5) the starting materials for carbohydrate synthesis are carbon dioxide and water
Answer
STROMA - THYLAKOID
Establish a correspondence between the processes and their localization in chloroplasts: 1) stroma, 2) thylakoid. Write numbers 1 and 2 in the order corresponding to the letters.
A) use of ATP
B) photolysis of water
B) stimulation of chlorophyll
D) formation of pentose
D) electron transfer along the enzyme chain
Answer
1. The features listed below, except two, are used to describe the structure and functions of the cell organelle depicted. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
2) accumulates ATP molecules
3) provides photosynthesis
5) has semi-autonomy
Answer
2. All of the characteristics listed below, except two, can be used to describe the cell organelle shown in the figure. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) single-membrane organelle
2) consists of cristae and chromatin
3) contains circular DNA
4) synthesizes its own protein
5) capable of division
Answer
The features listed below, except two, are used to describe the structure and functions of the cell organelle depicted. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated.
1) breaks down biopolymers into monomers
2) accumulates ATP molecules
3) provides photosynthesis
4) refers to double-membrane organelles
5) has semi-autonomy
Answer
LIGHT
1. Choose two correct answers out of five and write down the numbers under which they are indicated. During the light phase of photosynthesis in the cell
1) oxygen is formed as a result of the decomposition of water molecules
2) carbohydrates are synthesized from carbon dioxide and water
3) polymerization of glucose molecules occurs to form starch
4) ATP molecules are synthesized
5) the energy of ATP molecules is spent on the synthesis of carbohydrates
Answer
2. Identify three correct statements from the general list, and write down the numbers under which they are indicated in the table. During the light phase of photosynthesis occurs
1) photolysis of water
4) hydrogen connection with the NADP+ transporter
Answer
LIGHT EXCEPT
1. All of the signs below, except two, can be used to determine the processes of the light phase of photosynthesis. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) photolysis of water
2) reduction of carbon dioxide to glucose
3) synthesis of ATP molecules using the energy of sunlight
4) formation of molecular oxygen
5) use of the energy of ATP molecules for the synthesis of carbohydrates
Answer
2. All of the characteristics listed below, except two, can be used to describe the light phase of photosynthesis. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) a by-product is formed - oxygen
2) occurs in the stroma of the chloroplast
3) binding of carbon dioxide
4) ATP synthesis
5) photolysis of water
Answer
3. All of the characteristics listed below, except two, are used to describe the stage of photosynthesis shown in the figure. Identify two characteristics that “fall out” from the general list and write down the numbers under which they are indicated. At this stage
1) glucose synthesis occurs
2) the Calvin cycle begins
3) ATP is synthesized
4) photolysis of water occurs
5) hydrogen combines with NADP
Answer
DARK
Choose three options. The dark phase of photosynthesis is characterized by
1) the occurrence of processes on the internal membranes of chloroplasts
2) glucose synthesis
3) fixation of carbon dioxide
4) the course of processes in the stroma of chloroplasts
5) the presence of photolysis of water
6) ATP formation
Answer
DARK EXCEPT
1. The concepts listed below, except two, are used to describe the dark phase of photosynthesis. Identify two concepts that “fall out” from the general list and write down the numbers under which they are indicated.
2) photolysis
3) oxidation of NADP 2H
4) grana
5) stroma
Answer
2. All of the characteristics listed below, except two, are used to describe the dark phase of photosynthesis. Identify two characteristics that “drop out” from the general list and write down the numbers under which they are indicated.
1) oxygen formation
2) carbon dioxide fixation
3) use of ATP energy
4) glucose synthesis
5) stimulation of chlorophyll
Answer
LIGHT - DARK
1. Establish a correspondence between the process of photosynthesis and the phase in which it occurs: 1) light, 2) dark. Write numbers 1 and 2 in the correct order.
A) formation of NADP-2H molecules
B) release of oxygen
B) monosaccharide synthesis
D) synthesis of ATP molecules
D) addition of carbon dioxide to carbohydrate
Answer
2. Establish a correspondence between the characteristic and the phase of photosynthesis: 1) light, 2) dark. Write numbers 1 and 2 in the correct order.
A) photolysis of water
B) carbon dioxide fixation
B) splitting of ATP molecules
D) excitation of chlorophyll by light quanta
D) glucose synthesis
Answer
3. Establish a correspondence between the process of photosynthesis and the phase in which it occurs: 1) light, 2) dark. Write numbers 1 and 2 in the correct order.
A) formation of NADP*2H molecules
B) release of oxygen
B) glucose synthesis
D) synthesis of ATP molecules
D) reduction of carbon dioxide
Answer
4. Establish a correspondence between the processes and the phase of photosynthesis: 1) light, 2) dark. Write numbers 1 and 2 in the order corresponding to the letters.
A) polymerization of glucose
B) carbon dioxide binding
B) ATP synthesis
D) photolysis of water
D) formation of hydrogen atoms
E) glucose synthesis
Answer
5. Establish a correspondence between the phases of photosynthesis and their characteristics: 1) light, 2) dark. Write numbers 1 and 2 in the order corresponding to the letters.
A) photolysis of water occurs
B) ATP is formed
B) oxygen is released into the atmosphere
D) proceeds with the expenditure of ATP energy
D) reactions can occur both in light and in darkness
Answer
6 Sat. Establish a correspondence between the phases of photosynthesis and their characteristics: 1) light, 2) dark. Write numbers 1 and 2 in the order corresponding to the letters.
A) restoration of NADP+
B) transport of hydrogen ions across the membrane
B) occurs in the grana of chloroplasts
D) carbohydrate molecules are synthesized
D) chlorophyll electrons move to a higher energy level
E) ATP energy is consumed
Answer
FORMING 7:
A) movement of excited electrons
B) conversion of NADP-2R to NADP+
B) oxidation of NADPH
D) molecular oxygen is formed
D) processes occur in the stroma of the chloroplast
SUBSEQUENCE
1. Establish the correct sequence of processes occurring during photosynthesis. Write down the numbers under which they are indicated in the table.
1) Use of carbon dioxide
2) Oxygen formation
3) Carbohydrate synthesis
4) Synthesis of ATP molecules
5) Excitation of chlorophyll
Answer
2. Establish the correct sequence of photosynthesis processes.
1) transformation solar energy into ATP energy
2) formation of excited electrons of chlorophyll
3) carbon dioxide fixation
4) formation of starch
5) conversion of ATP energy into glucose energy
Answer
3. Establish the sequence of processes occurring during photosynthesis. Write down the corresponding sequence of numbers.
1) carbon dioxide fixation
2) ATP breakdown and energy release
3) glucose synthesis
4) synthesis of ATP molecules
5) stimulation of chlorophyll
Answer
PHOTOSYNTHESIS
Select cell organelles and their structures involved in the process of photosynthesis.
1) lysosomes
2) chloroplasts
3) thylakoids
4) grains
5) vacuoles
6) ribosomes
Answer
PHOTOSYNTHESIS EXCEPT
All but two of the following characteristics can be used to describe the process of photosynthesis. Identify two characteristics that “drop out” from the general list, and write down the numbers under which they are indicated in your answer.
1) Light energy is used to carry out the process.
2) The process occurs in the presence of enzymes.
3) The central role in the process belongs to the chlorophyll molecule.
4) The process is accompanied by the breakdown of the glucose molecule.
5) The process cannot occur in prokaryotic cells.
Answer
Analyze the table. Fill in the blank cells of the table using the concepts and terms given in the list. For each lettered cell, select the appropriate term from the list provided.
1) thylakoid membranes
2) light phase
3) fixation of inorganic carbon
4) photosynthesis of water
5) dark phase
6) cell cytoplasm
Answer
Analyze the table “Reactions of Photosynthesis”. For each letter, select the corresponding term from the list provided.
1) oxidative phosphorylation
2) oxidation of NADP-2H
3) thylakoid membranes
4) glycolysis
5) addition of carbon dioxide to pentose
6) oxygen formation
7) formation of ribulose diphosphate and glucose
8) synthesis of 38 ATP
Answer
Insert into the text “Synthesis of organic substances in a plant” the missing terms from the proposed list, using numerical notations. Write down the selected numbers in the order corresponding to the letters. Plants store the energy necessary for their existence in the form of organic substances. These substances are synthesized during __________ (A). This process occurs in leaf cells in __________ (B) - special green plastids. They contain a special green substance – __________ (B). A prerequisite for the formation of organic substances in addition to water and carbon dioxide is __________ (D).
List of terms:
1) breathing
2) evaporation
3) leukoplast
4) food
5) light
6) photosynthesis
7) chloroplast
8) chlorophyll
Answer
Establish a correspondence between the stages of the process and the processes: 1) photosynthesis, 2) protein biosynthesis. Write numbers 1 and 2 in the correct order.
A) release of free oxygen
B) formation of peptide bonds between amino acids
B) synthesis of mRNA on DNA
D) translation process
D) restoration of carbohydrates
E) conversion of NADP+ to NADP 2H
Answer
© D.V. Pozdnyakov, 2009-2019
Plants convert sunlight into stored chemical energy in two steps: first, they capture the energy from sunlight and then use it to fix carbon to form organic molecules.
Green plants - biologists call them autotrophs- 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 ( cm. Biological molecules), of which the most important is the six-carbon sugar glucose. This energy conversion process is called photosynthesis. Other living organisms access this energy by eating plants. This creates a food chain that supports the planetary ecosystem.
In addition, the air we breathe is saturated with oxygen thanks to photosynthesis. The overall equation for photosynthesis looks like this:
water + carbon dioxide + light → carbohydrates + oxygen
Plants absorb carbon dioxide produced during respiration and release oxygen, a waste product of plants ( cm. Glycolysis and respiration). In addition, photosynthesis plays a critical role in the carbon cycle in nature.
It seems surprising that, despite the importance of photosynthesis, scientists did not begin to study it for so long. After Van Helmont's experiment, carried out in the 17th century, there was a lull, and only in 1905 the English plant physiologist Frederick Blackman (1866-1947) conducted research and established the basic processes of photosynthesis. He showed that photosynthesis begins in low light, that the rate of photosynthesis increases with increasing light flux, but, starting from a certain level, further increases in lighting no longer lead to an increase in photosynthetic activity. Blackman showed that increasing temperature under low light conditions had no effect on the rate of photosynthesis, but that when temperature and light were increased simultaneously, the rate of photosynthesis increased significantly more than with increased light alone.
From these experiments, 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 - molecules chlorophyll. Chlorophyll is found in leaf cells and in the membranes of cellular organelles chloroplasts(they are the ones who 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 ( cm. Biological molecules). Meanwhile, a slightly different Photosystem I chlorophyll molecule absorbs the photon's energy 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. (I note that as a result of another, much less efficient process involving Photosystem I alone, ATP molecules are also formed.) After solar energy is absorbed and stored, it is the turn of the formation of carbohydrates. The basic mechanism for the synthesis of carbohydrates in plants was discovered by Melvin Calvin, who carried out a series of experiments in the 1940s that have now become classic. Calvin and his collaborators grew the algae in the presence of carbon dioxide containing radioactive carbon-14. They were able to establish the chemical reactions of the dark phase by interrupting photosynthesis at different stages.
The cycle of conversion of solar energy into carbohydrates - the so-called Calvin cycle - is similar to the Krebs cycle ( cm. Glycolysis and respiration: It also 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.
In most plants, the Calvin cycle described above occurs, in which carbon dioxide, directly participating in reactions, binds to ribulose diphosphate. These plants are called C 3 plants because the carbon dioxide-ribulose diphosphate complex is broken down into two smaller molecules, each consisting of three carbon atoms. Some plants (such as corn and sugarcane, and many tropical grasses, including creeping weed) operate differently. The fact is that carbon dioxide normally penetrates through holes in the surface of the sheet, called stomata. At high temperatures, the stomata close, protecting the plant from excessive moisture loss. In C 3 plants, when the stomata are closed, the supply of carbon dioxide also stops, which leads to a slowdown in photosynthesis and a change in photosynthetic reactions. In the case of corn, carbon dioxide attaches to a three-carbon molecule on the surface of the leaf, then moves to the interior of the leaf, where the carbon dioxide is released and the Calvin cycle begins. Thanks to this rather complex process, photosynthesis in corn occurs even in very hot, dry weather. We call plants in which this process occurs C 4 plants, since carbon dioxide is transported as a four-carbon molecule at the beginning of the cycle. C 3 -plants are mainly temperate plants, while C 4 -plants are mainly found in the tropics.
Van Niel hypothesis
The process of photosynthesis is described by the following chemical reaction:
CO 2 + H 2 O + light → carbohydrate + O 2
At the beginning of the 20th century, it was believed that the oxygen released during photosynthesis was formed as a result of the breakdown of carbon dioxide. This point of view was refuted in the 1930s by Cornelis Bernardus Van Niel (1897-1986), then a graduate student at Stanford University in California. He studied the purple sulfur bacterium (pictured), which requires hydrogen sulfide (H 2 S) for photosynthesis and releases atomic sulfur as a by-product. For such bacteria, the photosynthesis equation looks like this:
CO 2 + H 2 S + light → carbohydrate + 2S.
Based on the similarity of these two processes, Van Niel suggested that in ordinary photosynthesis the source of oxygen is not carbon dioxide, but water, since in sulfur bacteria, which metabolize sulfur instead of oxygen, photosynthesis returns this sulfur, which is a by-product of photosynthetic reactions. The modern detailed explanation of photosynthesis confirms this conjecture: the first stage of the photosynthetic process (carried out in Photosystem II) is the splitting of a water molecule.
Photosynthesis occurs in plants (mainly in their leaves) in the light. This is a process in which the organic substance glucose (one of the types of sugars) is formed from carbon dioxide and water. Next, glucose in the cells is converted into a more complex substance, starch. Both glucose and starch are carbohydrates.
The process of photosynthesis not only produces organic matter, but also produces oxygen as a by-product.
Carbon dioxide and water are inorganic substances, while glucose and starch are organic. Therefore, it is often said that photosynthesis is the process of formation of organic substances from inorganic substances in the light. Only plants, some single-celled eukaryotes, and some bacteria are capable of photosynthesis. There is no such process in the cells of animals and fungi, so they are forced to absorb organic substances from the environment. In this regard, plants are called autotrophs, and animals and fungi are called heterotrophs.
The process of photosynthesis in plants occurs in chloroplasts, which contain the green pigment chlorophyll.
So, for photosynthesis to occur, you need:
chlorophyll,
carbon dioxide.
During the process of photosynthesis the following are formed:
organic matter,
oxygen.
Plants are adapted to capture light. For many herbaceous plants the leaves are collected in a so-called basal rosette, when the leaves do not shade each other. Trees are characterized by a leaf mosaic, in which the leaves grow in such a way as to shade each other as little as possible. In plants, leaf blades can turn towards the light due to the bending of the leaf petioles. With all this, there are shade-loving plants that can only grow in the shade.
Water for photosynthesis enters the leaves from the roots along the stem. Therefore, it is important that the plant receives enough moisture. With a lack of water and certain minerals, the process of photosynthesis is inhibited.
Carbon dioxide for photosynthesis is taken directly from the air by the leaves. Oxygen, which is produced by the plant during photosynthesis, on the contrary, is released into the air. Gas exchange is facilitated by intercellular spaces (spaces between cells).
Organic substances formed during the process of photosynthesis are partly used in the leaves themselves, but mainly flow into all other organs and are converted into other organic substances, used in energy metabolism, and converted into reserve nutrients.
Human life, like all living things on Earth, is impossible without breathing. We inhale oxygen from the air and exhale carbon dioxide. But why doesn't the oxygen run out? It turns out that the air in the atmosphere is continuously supplied with oxygen. And this saturation occurs precisely thanks to photosynthesis.
Photosynthesis - simple and clear!
Every person must understand what photosynthesis is. To do this, you don’t need to write complex formulas at all; it’s enough to understand the importance and magic of this process.
The main role in the process of photosynthesis is played by plants - grass, trees, shrubs. It is in the leaves of plants that, over millions of years, the amazing transformation of carbon dioxide into oxygen occurs, which is so necessary for life for those who like to breathe. Let's try to analyze the entire process of photosynthesis in order.
1. Plants take water from the soil with minerals dissolved in it - nitrogen, phosphorus, manganese, potassium, various salts - more than 50 different ones in total chemical elements. Plants need this for nutrition. But plants receive only 1/5 of the necessary substances from the ground. The remaining 4/5 they get out of thin air!
2. Plants absorb carbon dioxide from the air. The same carbon dioxide that we exhale every second. Plants breathe carbon dioxide, just as we breathe oxygen. But this is not enough.
3. An irreplaceable component in a natural laboratory is sunlight. The sun's rays in the leaves of plants awaken an extraordinary chemical reaction. How does this happen?
4. There is an amazing substance in the leaves of plants - chlorophyll. Chlorophyll is able to capture streams of sunlight and tirelessly process the resulting water, microelements, and carbon dioxide into organic substances necessary for every living creature on our planet. At this moment, plants release oxygen into the atmosphere! It is this work of chlorophyll that scientists call a complex word - photosynthesis.
A presentation on the topic Photosynthesis can be downloaded on the educational portal
So why is the grass green?
Now that we know that plant cells contain chlorophyll, this question is very easy to answer. No wonder chlorophyll is translated from ancient Greek as “ green leaf" For photosynthesis, chlorophyll uses all rays of sunlight except green. We see grass and plant leaves green precisely because chlorophyll turns out green.
The meaning of photosynthesis.
The importance of photosynthesis cannot be overestimated - without photosynthesis, too much carbon dioxide would accumulate in the atmosphere of our planet, most living organisms simply would not be able to breathe and would die. Our Earth would turn into a lifeless planet. In order to prevent this, every person on planet Earth must remember that we are very much indebted to plants.
This is why it is so important to create as many parks and green spaces in cities as possible. Protect the taiga and jungle from destruction. Or just plant a tree next to your house. Or don't break branches. Only the participation of every person on planet Earth will help preserve life on our home planet.
But the importance of photosynthesis goes beyond converting carbon dioxide into oxygen. It was as a result of photosynthesis that the ozone layer was formed in the atmosphere, protecting the planet from the harmful rays of ultraviolet radiation. Plants are food for most living things on Earth. Food is necessary and healthy. The nutritional value of plants is also the result of photosynthesis.
Recently, chlorophyll has been actively used in medicine. People have long known that sick animals instinctively eat green leaves to heal. Scientists have found that chlorophyll is similar to a substance in human blood cells and can work real miracles.
Plants receive everything they need for growth and development from the environment. This is how they differ from other living organisms. In order for them to develop well, they need fertile soil, natural or artificial watering and good lighting. Nothing will grow in the dark.
Soil is a source of water and nutritious organic compounds and microelements. But trees, flowers, and grass also need solar energy. It is under the influence of sunlight that certain reactions occur, as a result of which carbon dioxide absorbed from the air is converted into oxygen. This process is called photosynthesis. The chemical reaction that occurs under the influence of sunlight also leads to the formation of glucose and water. These substances are vital for the plant to develop.
In the language of chemists, the reaction looks like this: 6CO2 + 12H2O + light = C6H12O6 + 6O2 + 6H2O. A simplified form of the equation: carbon dioxide + water + light = glucose + oxygen + water.
Literally, “photosynthesis” is translated as “together with light.” This word consists of two simple words"photo" and "synthesis". The sun is a very powerful source of energy. People use it to generate electricity, insulate houses, and heat water. Plants also need energy from the sun to sustain life. Glucose, produced during photosynthesis, is a simple sugar that is one of the most important nutrients. Plants use it for growth and development, and the excess is deposited in leaves, seeds, and fruits. Not all of the glucose remains unchanged in the green parts of plants and fruits. Simple sugars tend to transform into more complex ones, which include starch. Plants use up such reserves during periods of nutrient shortage. They determine the nutritional value of herbs, fruits, flowers, leaves for animals and people who eat plant foods.
How do plants absorb light?
The process of photosynthesis is quite complex, but it can be described briefly so that it becomes understandable even for children school age. One of the most common questions concerns the mechanism of light absorption. How does light energy get into plants? The process of photosynthesis occurs in the leaves. The leaves of all plants contain green cells - chloroplasts. They contain a substance called chlorophyll. Chlorophyll is a pigment that gives leaves green color and is responsible for absorbing light energy. Many people have not thought about why the leaves of most plants are wide and flat. It turns out that nature provided this for a reason. The wide surface allows you to absorb more sunlight. For the same reason, solar panels are made wide and flat.
The upper part of the leaves is protected by a waxy layer (cuticle) from water loss and the adverse effects of weather and pests. It is called palisade. If you look closely at the leaf, you can see that its upper side is brighter and smoother. The rich color is obtained due to the fact that there are more chloroplasts in this part. Excess light can reduce the plant's ability to produce oxygen and glucose. When exposed to bright sun, chlorophyll is damaged and this slows down photosynthesis. A slowdown also occurs with the arrival of autumn, when there is less light, and the leaves begin to turn yellow due to the destruction of chloroplasts in them.
The role of water in photosynthesis and in maintaining plant life cannot be underestimated. Water is needed for:
- providing plants with minerals dissolved in it;
- maintaining tone;
- cooling;
- the possibility of chemical and physical reactions occurring.
Trees, shrubs, and flowers absorb water from the soil with their roots, and then the moisture rises along the stem and passes into the leaves along veins that are visible even to the naked eye.
Carbon dioxide enters through small holes at the bottom of the leaf - stomata. In the lower part of the leaf, the cells are arranged in such a way that carbon dioxide can penetrate more deeply. This also allows the oxygen produced by photosynthesis to easily leave the leaf. Like all living organisms, plants are endowed with the ability to breathe. Moreover, unlike animals and people, they absorb carbon dioxide and release oxygen, and not vice versa. Where there are a lot of plants, the air is very clean and fresh. This is why it is so important to take care of trees and shrubs and create public gardens and parks in large cities.
Light and dark phases of photosynthesis
The process of photosynthesis is complex and consists of two phases - light and dark. The light phase is only possible in the presence of sunlight. When exposed to light, chlorophyll molecules ionize, resulting in energy that serves as a catalyst for chemical reactions. The order of events occurring in this phase is as follows:
- light hits the chlorophyll molecule, which is absorbed by the green pigment and puts it into an excited state;
- water splits;
- ATP is synthesized, which is an energy accumulator.
The dark phase of photosynthesis occurs without the participation of light energy. At this stage, glucose and oxygen are formed. It is important to understand that the formation of glucose and oxygen occurs around the clock, and not just at night. The dark phase is called because the presence of light is no longer necessary for it to occur. The catalyst is ATP, which was synthesized earlier.
The importance of photosynthesis in nature
Photosynthesis is one of the most significant natural processes. It is necessary not only to maintain plant life, but also for all life on the planet. Photosynthesis is needed for:
- providing animals and people with food;
- removing carbon dioxide and saturating the air with oxygen;
- maintaining nutrient cycling.
All plants depend on the rate of photosynthesis. Solar energy can be seen as a factor that promotes or inhibits growth. For example, in the southern regions and areas there is a lot of sun and plants can grow quite tall. If we consider how the process occurs in aquatic ecosystems, on the surface of the seas and oceans there is no shortage of sun rays and in these layers there is abundant growth of algae. In deeper layers of water there is a shortage of solar energy, which affects the growth rate of aquatic flora.
The process of photosynthesis contributes to the formation of the ozone layer in the atmosphere. This is very important as it helps protect all life on the planet from the harmful effects of ultraviolet rays.
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