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Photosynthesis Definition, Equation, Diagram, Process

Among all living organisms, only green plants and some other organisms like Algae and Cyanobacteria are Autotrophs or Phototrophs i.e., they make their own food by the process of Photosynthesis. Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose, a type of sugar. It takes place in the chloroplast of the plant cell.

What is Photosynthesis?

Photosynthesis is the process in which a plant uses sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar. Photosynthesis can be influenced by a variety of environmental factors, including temperature and light intensity. In the process of Photosynthesis green plants use sunlight, carbon dioxide (CO2), and water (H2O) for preparing food. During Photosynthesis, plants take Carbon dioxide (CO2) and release Oxygen (O2) and chemical energy stored in the form of Glucose. Photosynthesis is of two different types: Oxygenic Photosynthesis and Anoxygenic Photosynthesis.

Photosynthesis Definition, Equation, Diagram, Process_3.1

Process of Photosynthesis

It’s a vital biological process that supports life on Earth by creating glucose (a type of sugar) and oxygen through the utilization of carbon dioxide, water, and chlorophyll. Glucose produced at the time of photosynthesis serves as a primary source of energy for plants and is used in various cellular processes. The oxygen produced during photosynthesis is used by living organisms in the process of cellular respiration.

This process takes place in a unique structure called Chloroplast which is found mainly on the leaves. The chloroplast contains a green pigment called chlorophyll. This chlorophyll helps in capturing light energy. Photosynthesis is very important for Terrestrial and Aquatic ecosystems, as it helps in the growth and development of plants and algae.

Carbon dioxide + Water + Sunlight → Glucose + Oxygen

Stages of Photosynthesis

The process of Photosynthesis consists of two main stages: the light-dependent reaction and the light-independent reaction [also known as Calvin Cycle]. Below we have briefly discussed about both stages of photosynthesis.

  • Light-Dependent Reaction
  • Light- Independent Reaction
Stages of Photosynthesis
Stages Description
Light-Dependent Reaction Plants convert light energy into chemical energy, forming glucose and oxygen, in light-dependent reactions.
Light-Independent Reaction Carbon dioxide combines with stored energy to create glucose in a light-independent reaction. It is also known as the Calvin Cycle.

Light Dependent Reaction

This reaction takes place in the Thylakoid membrane (an internal system of interconnected membranes, that carry out the light reaction) of the chloroplast. The chlorophyll absorbs the light energy which is used to break water molecules into Oxygen and Protons then this Oxygen is released into the atmosphere while the protons are used to form energy-rich molecules like ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).

Photosynthesis Definition, Equation, Diagram, Process_4.1

Light Independent Reaction

The light-dependent reaction is also known as the Calvin Cycle. The cycle is named after Melvin Calvin who gave its mechanism in the 20th century. The light-dependent reaction takes place in the Stroma (a fluid-filled internal space of the chloroplast, it contains the DNA of the chloroplast, starch, ribosomes, and all the enzymes needed in the Calvin cycle) of the chloroplast. Through numerous chemical reactions, ATP’s energy and NADPH’s reducing power play a crucial role in converting carbon dioxide into glucose.

Photosynthesis Equation and Formula

Photosynthesis is the fundamental biological process that helps to maintain a balance of energy and carbon in our biosphere. The chemical equation for photosynthesis is an overall sum-up of the process. Photosynthesis can be simply described by the equation. Photosynthesis Equation can be written as

6CO2 + 6H2O → C6H12O6 + 6O2


  • 6CO2 means that there are six molecules of carbon dioxide.
  • 6H2O means that there are six molecules of water.
  • Light energy is used to make the reaction faster.
  • C6H12O6 means that there is only one molecule of glucose and it is the primary product of photosynthesis.
  • 6O2 means that there are six oxygen molecules formed in the reaction. The Oxygen is released as a byproduct of photosynthesis.

This is the simplest representation of Photosynthesis, as it is a complex reaction that involves multiple numbers of intermediate steps and various enzymes.

Types of Photosynthesis

There are mainly two types of photosynthesis and both play a crucial role in the maintenance of an environment in their own ways. One of them gives oxygen as a by-product while the other does not give oxygen as a by-product. The two types of photosynthesis are mentioned below:

  • Oxygenic Photosynthesis
  • Anoxygenic photosynthesis

Now let us discuss both types of Photosynthesis in a tabulated form.

Types of Photosynthesis
Types Description
Oxygenic Photosynthesis  Oxygenic photosynthesis is the process by which plants and cyanobacteria convert light into energy, producing oxygen.
Anoxygenic Photosynthesis Anoxygenic photosynthesis is a light-driven process in certain bacteria that don’t produce oxygen as a byproduct.

Oxygenic Photosynthesis

Oxygenic photosynthesis is the most common form of photosynthesis on Earth and it is very crucial for the production of oxygen. It is the process in which certain organisms such as plants, algae, and cyanobacteria, use sunlight to convert carbon dioxide and water into glucose and oxygen. Oxygenic photosynthesis is a complex process that takes place in the chloroplast of plants, blue-green algae, and cyanobacteria.

Oxygenic photosynthesis plays a great role in the maintenance of the ecosystem, as it provides the basis for food chains and energy flow in the biosphere. Oxygenic Photosynthesis increases the level of oxygen in the atmosphere, which allows the development of complex, oxygen-dependent life forms.

Anoxygenic Photosynthesis

Anoxygenic photosynthesis is a type of photosynthesis that occurs in certain bacteria including purple bacteria, and green sulfur bacteria, and does not give oxygen as a byproduct. These bacteria have a specialized light-absorbing pigment called Bacteriochlorophyll that helps to capture light energy. Anoxygenic photosynthesis uses electron donors such as hydrogen sulfide, ferrous iron, or organic compounds like succinate other than water.

This process is different from oxygenic photosynthesis. Anoxygenic photosynthesis plays a very crucial role in the carbon cycle. Anoxygenic photosynthesis is typically found in environments with low energy levels such as anaerobic mud, and aquatic sediments, and certain extreme environments like hot springs.

Importance of Photosynthesis

Photosynthesis is the process of preparing food in the presence of sunlight, water, carbon dioxide, and chlorophyll as mentioned above. Photosynthesis is very important as it is the fundamental process that helps to sustain life on Earth. Photosynthesis plays a very important role in the existence of all living organisms on earth, maintains the plant’s ecological balance, and provides food and energy for all living organisms. Without photosynthesis, life will be not possible on the Earth, and the ecosystem of the Earth will drastically change.

Now let us discuss the importance of photosynthesis:

  1. Photosynthesis helps plants prepare their food, and then these plants are consumed by almost all living organisms.
  2. During the process of Photosynthesis, plants use Carbon dioxide and release Oxygen which is essential for all living organisms. Photosynthesis also maintains the level of Oxygen (O2) and Carbon dioxide (CO2) in the Earth’s atmosphere.
  3. Through photosynthesis green plants, algae, and cyanobacteria convert solar energy to chemical energy in the form of Glucose.
  4. Photosynthesis also forms the basis of the Food Chain and Food Webs within the ecosystem, as it provides energy to producers (plants) which are then consumed by the consumers in various ecosystems.
  5. The organic matter produced at the time of Photosynthesis gets buried over a million years, which leads to the formation of fossil fuels.

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Photosynthesis : FAQs

Q1: What is photosynthesis?

Ans. Photosynthesis is the process where plants convert sunlight into energy, producing oxygen and glucose.

Q2. What are the different types of photosynthesis?

Ans. There are two different types of photosynthesis: Oxygenic photosynthesis and Anoxygenic photosynthesis.

Q3. How many oxygen molecules are formed during Photosynthesis?

Ans. Almost six oxygen molecules are formed at the time of Photosynthesis.

Q4. Where does the process of photosynthesis takes place in plants?

Ans. Photosynthesis takes place inside the chloroplast of the leaves.

Q5. What is the chemical equation for photosynthesis?

Ans. The chemical equation for photosynthesis is 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2.

Q6. What are the different stages of Photosynthesis?

Ans: The process of photosynthesis is divided into two stages: Light dependent reaction and Light independent reaction.

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