how to balance chemical equation of photosynthesis

The Balanced Chemical Equation for Photosynthesis

Photosynthesis Overall Chemical Reaction

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Photosynthesis is the process in plants and certain other organisms that uses the energy from the sun to convert carbon dioxide and water into glucose (a sugar) and oxygen.

Here is the balanced equation for the overall reaction:

6 CO 2  + 6 H 2 O → C 6 H 12 O 6  + 6 O 2  

Where: CO 2  = carbon dioxide   H 2 O = water light is required C 6 H 12 O 6  = glucose O 2  = oxygen

Explanation

In words, the equation may be stated as: Six carbon dioxide molecules and six water molecules react to produce one glucose molecule and six oxygen molecules .

The reaction requires energy in the form of light to overcome the activation energy needed for the reaction to proceed. Carbon dioxide and water don't spontaneously convert into glucose and oxygen .

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• Chloroplast Function in Photosynthesis
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Photosynthesis – Equation, Formula & Products

Core concepts.

In this tutorial, you will learn all about photosynthesis . We begin with an introduction to photosynthesis and its balanced chemical equation. Then, we analyze the two key stages involved in this process and take a look at the final products. Lastly, we consider the different types of photosynthesis.

Topics Covered in Other Articles

• What is a Chemical Reaction? Physical vs Chemical Change Examples
• What is a Reactant in Chemistry?
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• Common Oxidizing Agents & Reducing Agents
• What is Gluconeogenesis?

Introduction to Photosynthesis

The process by which plants and other organisms convert light energy (sunlight) into chemical energy (glucose) is known as photosynthesis. Sunlight powers a series of reactions that use water and carbon dioxide to synthesize glucose and release oxygen as a byproduct. Energy is stored in the chemical bonds of glucose and can be later harvested to fuel the organism’s activities through cellular respiration or fermentation .

Photosynthesis is an endergonic process because it requires an input of energy from the surroundings in order for a chemical change to take place. Furthermore, photosynthesis is a reduction-oxidation (redox) reaction , meaning that it involves the transfer of electrons between chemical species. During the process, carbon dioxide is reduced (i.e., gains electrons) to form glucose, and water is oxidized (i.e., loses electrons) to form molecular oxygen.

The complex process of photosynthesis takes place in chloroplasts (i.e., membrane-bound organelles in plant and algal cells). Chloroplasts have an outer membrane and an inner membrane. The stroma is the fluid-filled space within the inner membrane; it surrounds flattened sac-like structures known as thylakoids. Thylakoids consist of a thylakoid space (lumen) surrounded by a thylakoid membrane. The thylakoid membrane contains photosystems, which are large complexes of proteins and pigments. There are two types of photosystems: photosystem I (PSI) and photosystem II (PSII).

Chemical Equation for Photosynthesis

The overall balanced equation for photosynthesis is commonly written as 6 CO 2 + 6 H 2 O → C 6 H 12 O 6 + 6 O 2 (shown below). In other words, six molecules of carbon dioxide and six molecules of water react in the presence of sunlight to produce one molecule of glucose (a six-carbon sugar) and six molecules of oxygen. 

Stages of Photosynthesis

There are two main stages of photosynthesis: the light-dependent reactions and the Calvin cycle.

Light-Dependent Reactions

The light-dependent reactions use light energy to make ATP (an energy-carrying molecule) and NADPH (an electron carrier) for use in the Calvin cycle. In addition, oxygen is released as a result of the oxidation of water. In plants and algae, the light-dependent reactions take place in the thylakoid membrane of chloroplasts. The most common form of the light-dependent reactions is a process known as non-cyclic photophosphorylation. This process involves two key steps: ATP synthesis (via photosystem II) and NADPH synthesis (via photosystem I).

• Step 1 (ATP Synthesis): Pigments in photosystem II (such as chlorophylls) absorb light and energize electrons. A proton gradient is formed as these excited electrons travel down an electron transport chain and release energy that pumps hydrogen ions from the stroma to the thylakoid lumen. The splitting of water molecules through photolysis produces hydrogen ions (as well as oxygen molecules) that further contribute to this electrochemical gradient. As hydrogen ions flow down their gradient (i.e., back across the thylakoid membrane and into the stroma), they travel through an enzyme known as ATP synthase. ATP synthase catalyzes the formation of adenosine triphosphate (ATP) using ADP (adenosine diphosphate) and inorganic phosphate (P i ).
• Step 2 (NADPH Synthesis): Electrons are transferred to photosystem I and energized by the light absorbed by PSI pigments. The electrons reach the end of the electron transport chain and are passed to an enzyme known as ferredoxin-NADP + reductase (FNR). FNR catalyzes the reaction by which NADP + is reduced to NADPH.

Calvin Cycle

The Calvin cycle (also referred to as the light-independent reactions) takes place in the stroma of chloroplasts and is not directly dependent on sunlight. Instead, this stage utilizes the products of the light-dependent reactions (ATP and NADPH), along with carbon dioxide, to synthesize glucose. The Calvin cycle consists of three basic steps: carbon fixation, reduction, and regeneration.

• Step 1 (Carbon Fixation): RuBisCO (the most abundant enzyme on Earth) catalyzes the carboxylation of ribulose-1,5-biphosphate (RuBP) by carbon dioxide to produce an unstable six-carbon compound. This six-carbon compound is then readily converted into two molecules of 3-phosphoglyceric acid (3-PGA).
• Step 2 (Reduction): An enzyme known as phosphoglycerate kinase catalyzes the phosphorylation of 3-PGA by ATP to produce 1,3-biphosphoglyceric acid (1,3-BPG) and ADP. Next, another enzyme (glyceraldehyde 3-phosphate dehydrogenase) catalyzes the reduction of 1,3-BPG by NADPH to produce glyceraldehyde 3-phosphate (G3P) and NADP + .
• Step 3 (Regeneration): Every turn of the Calvin cycle produces two molecules of G3P. Therefore, six turns of the cycle produce twelve molecules of G3P. Two of these G3P molecules exit the cycle and are used to synthesize one molecule of glucose. Meanwhile, the other ten molecules of G3P remain in the cycle and are used to regenerate six RuBP molecules. The regeneration of RuBP requires ATP, but it allows the cycle to continue.

Products of Photosynthesis

The major product of photosynthesis is glucose, a simple sugar with the molecular formula C 6 H 12 O 6 . Plants and other photosynthetic organisms use glucose for numerous functions, including those listed below.

• Cellular Respiration: Glucose is broken down in order to produce ATP (which can be used to fuel other cellular activities) through a process known as cellular respiration.
• Biosynthesis of Starch and Cellulose: Glucose molecules can be linked together to form complex carbohydrates such as starch and cellulose. Plants and other organisms use starch to store energy and cellulose to support/rigidify their cell walls.
• Protein Synthesis: Glucose can be combined with nitrates (from the soil) to produce amino acids, which can then be used to build proteins.

In addition, oxygen is released into the atmosphere during the process of photosynthesis. Plants (along with many other organisms) use oxygen to carry out aerobic respiration.

Types of Photosynthesis

There are three main types of photosynthesis: C3, C4, and CAM (crassulacean acid metabolism). They differ in the way that they manage photorespiration, a wasteful process that occurs when the enzyme rubisco acts on oxygen instead of carbon dioxide. Photorespiration competes with the Calvin cycle and decreases the efficiency of photosynthesis (by wasting energy and using up fixed carbon).

C3 Photosynthesis

The majority of plants use C3 photosynthesis, a process in which no special features or adaptations are used to combat photorespiration. Hot, dry climates are not ideal for C3 plants (e.g., rice, wheat, and barley) because of the increased rate of photorespiration, which is due to the buildup of oxygen that occurs when plants close their stomata (leaf pores) in order to prevent water loss.

C4 Photosynthesis

C4 photosynthesis reduces photorespiration by performing the initial carbon dioxide fixation and Calvin cycle in two different cell types. This process utilizes an additional enzyme known as phosphoenolpyruvate (PEP) carboxylase. PEP carboxylase does not react with oxygen (unlike rubisco) and is able to catalyze a reaction between carbon dioxide and PEP in the mesophyll cells to produce the intermediate four-carbon compound oxaloacetate. Oxaloacetate is then reduced to malate and transported to bundle sheath cells. In these cells, malate undergoes decarboxylation, forming a special compartment for the concentration of carbon dioxide around rubisco.

As a result, the Calvin cycle can proceed as normal, and an opportunity for rubisco to bind to oxygen is prevented. C4 plants (e.g., maize and sugarcane) have a competitive advantage over C3 plants in hot, dry environments where the benefits of reduced photorespiration outweigh the additional energy costs associated with C4 photosynthesis.

CAM Photosynthesis

Crassulacean acid metabolism, also known as CAM photosynthesis, reduces photorespiration by performing the initial carbon dioxide fixation and Calvin cycle at separate times. CAM plants (e.g., cactus and pineapple) open their stomata at night, allowing carbon dioxide to enter the leaf. The carbon dioxide is converted to oxaloacetate by PEP carboxylase, the same enzyme used in C4 photosynthesis. Oxaloacetate is subsequently reduced to malate, which is stored as malic acid in vacuoles .

During the day (when light is readily available), CAM plants close their stomata and prepare for the Calvin cycle. Malate is transported into chloroplasts and broken down to release carbon dioxide, which is heavily concentrated around the enzyme rubisco. Similar to C4 photosynthesis, crassulacean acid metabolism is an energetically expensive process. However, it is quite useful for plants in hot, arid climates that need to minimize photorespiration and conserve water.

Further Reading

• What is Gibbs Free Energy?
• Endothermic vs Exothermic Reactions
• Catalysts & Activation Energy
• Proteins and Amino Acids
• Claisen Condensations

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General Education

The word photosynthesis comes from two Greek words: photo, meaning “light”, and synthesis, meaning “put together.” Looking at that those two roots, we have a good idea of what happens during the chemical process of photosynthesis: plants put together water and carbon dioxide with light to create glucose and oxygen.

In this article, we’ll break down what photosynthesis is, why photosynthesis is important, and discuss the chemical equation for photosynthesis: what it is and what each part of it means.

What Is Photosynthesis?

Put simply, photosynthesis is how plants, algae, and certain types of bacteria harness energy from sunlight to create chemical energy for themselves to live.

There are two main types of photosynthesis: oxygenic photosynthesis and anoxygenic photosynthesis. Oxygenic photosynthesis is more common—that’s the type we see in plants and algae. Anoxygenic photosynthesis mainly occurs in bacteria.

In oxygenic photosynthesis, plants use light energy to combine carbon dioxide (CO2) and water (H2O). This chemical reaction produces carbohydrates for the plants to consume and oxygen, which is released back into the air.

Anoxygenic photosynthesis is very similar, but it doesn’t produce oxygen. We’ll be focusing on the more common type of photosynthesis, oxygenic photosynthesis, for the rest of this article.

Why Is Photosynthesis Important?

Photosynthesis is important for a few reasons:

First, it produces energy that plants need to live. The resulting carbohydrates provide plants with the energy to grow and live.

Second, photosynthesis helps take in the carbon dioxide produced by breathing organisms and convert that into oxygen, which is then reintroduced back into the atmosphere. Basically, with photosynthesis, plants are helping produce the oxygen that all living things need to breathe and survive.

Photosynthesis Equation

Here is the chemical equation for photosynthesis:

6CO2 + 12H2O + Light Energy ------> C6H12O6 + 6O2 + 6H2O

Photosynthesis Formula Breakdown

Now that we know what the photosynthesis equation is, let’s break down each piece of the photosynthesis formula.

On the reactants side, we have:

6CO2 = Six molecules of carbon dioxide

12H2O = Twelve molecules of water

Light Energy = Light from the sun

On the products side, we have:

C6H12O6 = glucose

6O2 = six molecules of oxygen

6H2O = six molecules of water

As we learned earlier, the glucose will be used by the plant as energy. The oxygen and water will be released back into the atmosphere to help other living things.

What You Need to Know About the Photosynthesis Formula

During photosynthesis, plants use light energy to combine carbon dioxide and water to produce glucose, oxygen, and water.

Photosynthesis is important because it provides plants with the energy they need to survive. It also releases needed oxygen and water back into the atmosphere.

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Hayley Milliman is a former teacher turned writer who blogs about education, history, and technology. When she was a teacher, Hayley's students regularly scored in the 99th percentile thanks to her passion for making topics digestible and accessible. In addition to her work for PrepScholar, Hayley is the author of Museum Hack's Guide to History's Fiercest Females.

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Biology Wise

Balanced Photosynthesis Equation

The balanced equation for photosynthesis helps us to understand the process of glucose synthesis by plants in a simplified form. Read this write-up to gain more information about this subject.

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The presence of chlorophyll and the ability to undergo photosynthesis are some attributes that distinguish plants from animals. Photosynthesis is defined as the chemical process, wherein carbon dioxide in the presence of water and radiant energy gets converted to glucose (chemical energy), giving out oxygen as byproducts.

What is the Photosynthesis Equation?

Green plants along with algae and some bacteria are grouped under photoautotrophs, meaning they can make their own food in the presence of light by photosynthesis. This conversion of light energy into chemical energy occurs in the pigment containing plastids called chloroplasts.

The process that takes place in the chloroplasts for glucose production is put forth in the equation for photosynthesis. In the equation, the combining reactants and resulting products are expressed along with their respective numbers of molecules.

Balanced Photosynthesis Chemical Equation

Carbon dioxide, water, and radiant energy is present on the reactant side, whereas on the other side are the products of photosynthesis process, i.e., glucose and oxygen. Putting this in a simplified formula, the following equation represents this process.

Step 1 : CO 2 + H 2 O + Light energy → C 6 H 12 O 6 + O 2

A chemical reaction is said to be balanced, when both sides of the photosynthesis equation (reactants and products) have the same number of molecules for each of the elements.

Needless to mention, the above formula for photosynthesis is not balanced, as there is only one atom of carbon in the reactant side, while there are 6 carbon atoms in the product side. As you try to balance the above equation, put 6 in front of the carbon dioxide molecule, after which the resulting equation will be:

Step 2 : 6 CO 2 + H 2 O + Light energy → C 6 H 12 O 6 + O 2

Now, the number of carbon atoms is 6 in both sides. The remaining atoms to be balanced are hydrogen and oxygen. Hydrogen has only 2 atoms on the reactant side, and 12 atoms on the product side.

Thus, in order to balance the number of hydrogen atoms, place 6 in front of the water molecule in the reactant side. With this step, the partly balanced photosynthesis formula is represented by:

Step 3 : 6 CO 2 + 6 H 2 O + Light energy → C 6 H 12 O 6 + O 2

With this step, the numbers of carbon and hydrogen atoms are balanced on both sides of the photosynthesis equation. Thus, the final step is to balance the number of oxygen atoms.

Carefully calculate the number of oxygen atoms on the reactant side; i.e., 12 atoms from carbon dioxide (6 CO 2 ) and 6 atoms from water (6 H 2 O) form a total of 18 atoms. In the product side, there are 6 atoms from glucose (C 6 H 12 O 6 ) and 2 atoms from oxygen molecule (O 2 ) forming a total of 8 atoms.

And to balance the deficit atoms on the product side, put 6 in front of the oxygen molecule:

Step 4 : 6 CO 2 + 6 H 2 O + Light energy → C 6 H 12 O 6 + 6 O 2

So, this is how you can balance the photosynthesis equation in a step-by-step manner. It shows that six molecules each of carbon dioxide and water combine together in the presence of light energy, so as to form one glucose molecule and six oxygen molecules.

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8.1: Overview of Photosynthesis

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Skills to Develop

• Explain the relevance of photosynthesis to other living things
• Describe the main structures involved in photosynthesis
• Identify the substrates and products of photosynthesis
• Summarize the process of photosynthesis

Photosynthesis is essential to all life on earth; both plants and animals depend on it. It is the only biological process that can capture energy that originates in outer space (sunlight) and convert it into chemical compounds (carbohydrates) that every organism uses to power its metabolism. In brief, the energy of sunlight is captured and used to energize electrons, which are then stored in the covalent bonds of sugar molecules. How long lasting and stable are those covalent bonds? The energy extracted today by the burning of coal and petroleum products represents sunlight energy captured and stored by photosynthesis almost 200 million years ago.

Plants, algae, and a group of bacteria called cyanobacteria are the only organisms capable of performing photosynthesis (Figure \(\PageIndex{1}\)). Because they use light to manufacture their own food, they are called photoautotrophs (literally, “self-feeders using light”). Other organisms, such as animals, fungi, and most other bacteria, are termed heterotrophs (“other feeders”), because they must rely on the sugars produced by photosynthetic organisms for their energy needs. A third very interesting group of bacteria synthesize sugars, not by using sunlight’s energy, but by extracting energy from inorganic chemical compounds; hence, they are referred to as chemoautotrophs .

The importance of photosynthesis is not just that it can capture sunlight’s energy. A lizard sunning itself on a cold day can use the sun’s energy to warm up. Photosynthesis is vital because it evolved as a way to store the energy in solar radiation (the “photo-” part) as high-energy electrons in the carbon-carbon bonds of carbohydrate molecules (the “-synthesis” part). Those carbohydrates are the energy source that heterotrophs use to power the synthesis of ATP via respiration. Therefore, photosynthesis powers 99 percent of Earth’s ecosystems. When a top predator, such as a wolf, preys on a deer (Figure \(\PageIndex{2}\)), the wolf is at the end of an energy path that went from nuclear reactions on the surface of the sun, to light, to photosynthesis, to vegetation, to deer, and finally to wolf.

Main Structures and Summary of Photosynthesis

Photosynthesis is a multi-step process that requires sunlight, carbon dioxide (which is low in energy), and water as substrates (Figure \(\PageIndex{3}\)). After the process is complete, it releases oxygen and produces glyceraldehyde-3-phosphate (GA3P), simple carbohydrate molecules (which are high in energy) that can subsequently be converted into glucose, sucrose, or any of dozens of other sugar molecules. These sugar molecules contain energy and the energized carbon that all living things need to survive.

The following is the chemical equation for photosynthesis (Figure \(\PageIndex{4}\)):

Although the equation looks simple, the many steps that take place during photosynthesis are actually quite complex. Before learning the details of how photoautotrophs turn sunlight into food, it is important to become familiar with the structures involved.

In plants, photosynthesis generally takes place in leaves, which consist of several layers of cells. The process of photosynthesis occurs in a middle layer called the mesophyll . The gas exchange of carbon dioxide and oxygen occurs through small, regulated openings called stomata (singular: stoma), which also play roles in the regulation of gas exchange and water balance. The stomata are typically located on the underside of the leaf, which helps to minimize water loss. Each stoma is flanked by guard cells that regulate the opening and closing of the stomata by swelling or shrinking in response to osmotic changes.

In all autotrophic eukaryotes, photosynthesis takes place inside an organelle called a chloroplast . For plants, chloroplast-containing cells exist in the mesophyll. Chloroplasts have a double membrane envelope (composed of an outer membrane and an inner membrane). Within the chloroplast are stacked, disc-shaped structures called thylakoids . Embedded in the thylakoid membrane is chlorophyll, a pigment (molecule that absorbs light) responsible for the initial interaction between light and plant material, and numerous proteins that make up the electron transport chain. The thylakoid membrane encloses an internal space called the thylakoid lumen . As shown in Figure \(\PageIndex{5}\), a stack of thylakoids is called a granum , and the liquid-filled space surrounding the granum is called stroma or “bed” (not to be confused with stoma or “mouth,” an opening on the leaf epidermis).

Art Connection

On a hot, dry day, plants close their stomata to conserve water. What impact will this have on photosynthesis?

The Two Parts of Photosynthesis

Photosynthesis takes place in two sequential stages: the light-dependent reactions and the light independent-reactions. In the light-dependent reactions , energy from sunlight is absorbed by chlorophyll and that energy is converted into stored chemical energy. In the light-independent reactions , the chemical energy harvested during the light-dependent reactions drive the assembly of sugar molecules from carbon dioxide. Therefore, although the light-independent reactions do not use light as a reactant, they require the products of the light-dependent reactions to function. In addition, several enzymes of the light-independent reactions are activated by light. The light-dependent reactions utilize certain molecules to temporarily store the energy: These are referred to as energy carriers. The energy carriers that move energy from light-dependent reactions to light-independent reactions can be thought of as “full” because they are rich in energy. After the energy is released, the “empty” energy carriers return to the light-dependent reaction to obtain more energy. Figure\(\PageIndex{6}\) illustrates the components inside the chloroplast where the light-dependent and light-independent reactions take place.

Link to Learning

Click the link to learn more about photosynthesis.

Everyday Connection: Photosynthesis at the Grocery Store

Major grocery stores in the United States are organized into departments, such as dairy, meats, produce, bread, cereals, and so forth. Each aisle (Figure \(\PageIndex{7}\)) contains hundreds, if not thousands, of different products for customers to buy and consume.

Although there is a large variety, each item links back to photosynthesis. Meats and dairy link, because the animals were fed plant-based foods. The breads, cereals, and pastas come largely from starchy grains, which are the seeds of photosynthesis-dependent plants. What about desserts and drinks? All of these products contain sugar—sucrose is a plant product, a disaccharide, a carbohydrate molecule, which is built directly from photosynthesis. Moreover, many items are less obviously derived from plants: For instance, paper goods are generally plant products, and many plastics (abundant as products and packaging) are derived from algae. Virtually every spice and flavoring in the spice aisle was produced by a plant as a leaf, root, bark, flower, fruit, or stem. Ultimately, photosynthesis connects to every meal and every food a person consumes.

​​​​​Summary

The process of photosynthesis transformed life on Earth. By harnessing energy from the sun, photosynthesis evolved to allow living things access to enormous amounts of energy. Because of photosynthesis, living things gained access to sufficient energy that allowed them to build new structures and achieve the biodiversity evident today.

Only certain organisms, called photoautotrophs, can perform photosynthesis; they require the presence of chlorophyll, a specialized pigment that absorbs certain portions of the visible spectrum and can capture energy from sunlight. Photosynthesis uses carbon dioxide and water to assemble carbohydrate molecules and release oxygen as a waste product into the atmosphere. Eukaryotic autotrophs, such as plants and algae, have organelles called chloroplasts in which photosynthesis takes place, and starch accumulates. In prokaryotes, such as cyanobacteria, the process is less localized and occurs within folded membranes, extensions of the plasma membrane, and in the cytoplasm.

Art Connections

Figure \(\PageIndex{5}\): On a hot, dry day, plants close their stomata to conserve water. What impact will this have on photosynthesis?

Levels of carbon dioxide (a necessary photosynthetic substrate) will immediately fall. As a result, the rate of photosynthesis will be inhibited.

• Biology Article

Photosynthesis

Photosynthesis is a process by which phototrophs convert light energy into chemical energy, which is later used to fuel cellular activities. The chemical energy is stored in the form of sugars, which are created from water and carbon dioxide.

Table of Contents

• What is Photosynthesis?
• Site of photosynthesis

Photosynthesis definition states that the process exclusively takes place in the chloroplasts through photosynthetic pigments such as chlorophyll a, chlorophyll b, carotene and xanthophyll. All green plants and a few other autotrophic organisms utilize photosynthesis to synthesize nutrients by using carbon dioxide, water and sunlight. The by-product of the photosynthesis process is oxygen.Let us have a detailed look at the process, reaction and importance of photosynthesis.

What Is Photosynthesis in Biology?

The word “ photosynthesis ” is derived from the Greek words  phōs  (pronounced: “fos”) and σύνθεσις (pronounced: “synthesis “) Phōs means “light” and σύνθεσις   means, “combining together.” This means “ combining together with the help of light .”

Photosynthesis also applies to other organisms besides green plants. These include several prokaryotes such as cyanobacteria, purple bacteria and green sulfur bacteria. These organisms exhibit photosynthesis just like green plants.The glucose produced during photosynthesis is then used to fuel various cellular activities. The by-product of this physio-chemical process is oxygen.

A visual representation of the photosynthesis reaction

• Photosynthesis is also used by algae to convert solar energy into chemical energy. Oxygen is liberated as a by-product and light is considered as a major factor to complete the process of photosynthesis.
• Photosynthesis occurs when plants use light energy to convert carbon dioxide and water into glucose and oxygen. Leaves contain microscopic cellular organelles known as chloroplasts.
• Each chloroplast contains a green-coloured pigment called chlorophyll. Light energy is absorbed by chlorophyll molecules whereas carbon dioxide and oxygen enter through the tiny pores of stomata located in the epidermis of leaves.
• Another by-product of photosynthesis is sugars such as glucose and fructose.
• These sugars are then sent to the roots, stems, leaves, fruits, flowers and seeds. In other words, these sugars are used by the plants as an energy source, which helps them to grow. These sugar molecules then combine with each other to form more complex carbohydrates like cellulose and starch. The cellulose is considered as the structural material that is used in plant cell walls.

Where Does This Process Occur?

Chloroplasts are the sites of photosynthesis in plants and blue-green algae.  All green parts of a plant, including the green stems, green leaves,  and sepals – floral parts comprise of chloroplasts – green colour plastids. These cell organelles are present only in plant cells and are located within the mesophyll cells of leaves.

Also Read:  Photosynthesis Early Experiments

Photosynthesis Equation

Photosynthesis reaction involves two reactants, carbon dioxide and water. These two reactants yield two products, namely, oxygen and glucose. Hence, the photosynthesis reaction is considered to be an endothermic reaction. Following is the photosynthesis formula:

Unlike plants, certain bacteria that perform photosynthesis do not produce oxygen as the by-product of photosynthesis. Such bacteria are called anoxygenic photosynthetic bacteria. The bacteria that do produce oxygen as a by-product of photosynthesis are called oxygenic photosynthetic bacteria.

Structure Of Chlorophyll

The structure of Chlorophyll consists of 4 nitrogen atoms that surround a magnesium atom. A hydrocarbon tail is also present. Pictured above is chlorophyll- f,  which is more effective in near-infrared light than chlorophyll- a

Chlorophyll is a green pigment found in the chloroplasts of the  plant cell   and in the mesosomes of cyanobacteria. This green colour pigment plays a vital role in the process of photosynthesis by permitting plants to absorb energy from sunlight. Chlorophyll is a mixture of chlorophyll- a  and chlorophyll- b .Besides green plants, other organisms that perform photosynthesis contain various other forms of chlorophyll such as chlorophyll- c1 ,  chlorophyll- c2 ,  chlorophyll- d and chlorophyll- f .

Also Read:   Biological Pigments

Process Of Photosynthesis

At the cellular level,  the photosynthesis process takes place in cell organelles called chloroplasts. These organelles contain a green-coloured pigment called chlorophyll, which is responsible for the characteristic green colouration of the leaves.

As already stated, photosynthesis occurs in the leaves and the specialized cell organelles responsible for this process is called the chloroplast. Structurally, a leaf comprises a petiole, epidermis and a lamina. The lamina is used for absorption of sunlight and carbon dioxide during photosynthesis.

Structure of Chloroplast. Note the presence of the thylakoid

“Photosynthesis Steps:”

• During the process of photosynthesis, carbon dioxide enters through the stomata, water is absorbed by the root hairs from the soil and is carried to the leaves through the xylem vessels. Chlorophyll absorbs the light energy from the sun to split water molecules into hydrogen and oxygen.
• The hydrogen from water molecules and carbon dioxide absorbed from the air are used in the production of glucose. Furthermore, oxygen is liberated out into the atmosphere through the leaves as a waste product.
• Glucose is a source of food for plants that provide energy for  growth and development , while the rest is stored in the roots, leaves and fruits, for their later use.
• Pigments are other fundamental cellular components of photosynthesis. They are the molecules that impart colour and they absorb light at some specific wavelength and reflect back the unabsorbed light. All green plants mainly contain chlorophyll a, chlorophyll b and carotenoids which are present in the thylakoids of chloroplasts. It is primarily used to capture light energy. Chlorophyll-a is the main pigment.

The process of photosynthesis occurs in two stages:

• Light-dependent reaction or light reaction
• Light independent reaction or dark reaction

Stages of Photosynthesis in Plants depicting the two phases – Light reaction and Dark reaction

Light Reaction of Photosynthesis (or) Light-dependent Reaction

• Photosynthesis begins with the light reaction which is carried out only during the day in the presence of sunlight. In plants, the light-dependent reaction takes place in the thylakoid membranes of chloroplasts.
• The Grana, membrane-bound sacs like structures present inside the thylakoid functions by gathering light and is called photosystems.
• These photosystems have large complexes of pigment and proteins molecules present within the plant cells, which play the primary role during the process of light reactions of photosynthesis.
• There are two types of photosystems: photosystem I and photosystem II.
• Under the light-dependent reactions, the light energy is converted to ATP and NADPH, which are used in the second phase of photosynthesis.
• During the light reactions, ATP and NADPH are generated by two electron-transport chains, water is used and oxygen is produced.

The chemical equation in the light reaction of photosynthesis can be reduced to:

2H 2 O + 2NADP+ + 3ADP + 3Pi → O 2 + 2NADPH + 3ATP

Dark Reaction of Photosynthesis (or) Light-independent Reaction

• Dark reaction is also called carbon-fixing reaction.
• It is a light-independent process in which sugar molecules are formed from the water and carbon dioxide molecules.
• The dark reaction occurs in the stroma of the chloroplast where they utilize the NADPH and ATP products of the light reaction.
• Plants capture the carbon dioxide from the atmosphere through stomata and proceed to the Calvin photosynthesis cycle.
• In the Calvin cycle , the ATP and NADPH formed during light reaction drive the reaction and convert 6 molecules of carbon dioxide into one sugar molecule or glucose.

The chemical equation for the dark reaction can be reduced to:

3CO 2 + 6 NADPH + 5H 2 O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi

* G3P – glyceraldehyde-3-phosphate

Calvin photosynthesis Cycle (Dark Reaction)

Also Read:  Cyclic And Non-Cyclic Photophosphorylation

Importance of Photosynthesis

• Photosynthesis is essential for the existence of all life on earth. It serves a crucial role in the food chain – the plants create their food using this process, thereby, forming the primary producers.
• Photosynthesis is also responsible for the production of oxygen – which is needed by most organisms for their survival.

Frequently Asked Questions

1. what is photosynthesis explain the process of photosynthesis., 2. what is the significance of photosynthesis, 3. list out the factors influencing photosynthesis., 4. what are the different stages of photosynthesis, 5. what is the calvin cycle, 6. write down the photosynthesis equation..

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Please What Is Meant By 300-400 PPM

PPM stands for Parts-Per-Million. It corresponds to saying that 300 PPM of carbon dioxide indicates that if one million gas molecules are counted, 300 out of them would be carbon dioxide. The remaining nine hundred ninety-nine thousand seven hundred are other gas molecules.

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