What is Photosynthesis?

Photosynthesis is a chemical process through which plants, some protists and bacteria, produce glucose and oxygen from carbon dioxide using only light as a source of energy. This glucose, an energy unit, helps trees and plants to survive and grow. And since most living creatures on earth, directly or indirectly, depend on these green trees, the process of photosynthesis is considered as a very important one.

The Photosynthesis Reaction:                     

CO2 + H20 ----> C6H12O6 + O2      

Basically, in photosynthesis, carbon dioxide and water are converted into glucose and oxygen.
An Introduction to Photosynthesis:

If there is one process that sustains the skeleton of living organisms in this world, it is photosynthesis. Whilst this process is critical to maintain the normal level of oxygen in the atmosphere, almost all aerobic life, either directly or indirectly, depends on it for energy. Although photosynthesis can happen in different ways in different species, some features remain the same. Photosynthesis is the process by which plants use the energy from sunlight to produce sugar, which in simpler words is the 'fuel' used by all living things.

Photosynthesis is a chemical process through which plants, and some protists and bacteria, produce glucose and oxygen from carbon dioxide using light as the source. This glucose, an energy unit, helps trees and plants to survive and grow. Since most living creatures on earth, directly or indirectly, depend on these green trees, the process of photosynthesis is considered as a very important one.
The Reactions in Photosynthesis:

The process of photosynthesis, that plants feed on, divides itself in two sets of reactions, namely light-dependent reactions and light-independent reactions. As the names suggests, the light reactions need light to take place, while the later ones can perform independent of the light. Nonetheless, the presence of light is of utmost importance for photosynthesis, since the light-independent reactions, also known as dark reactions, eventually uses the chemical energy produced in the light reactions.

The light reactions uses the light from the sun to form energy carrying molecules, ATP and NADPH, which are then used in the following dark reactions of photosynthesis. The dark reactions, together known as the Calvin-Benson cycle, fix the atmospheric carbon dioxide in to organic molecules like glucose and other sugars.

Importance of Photosynthesis:

Photosynthesis is arguably the most important biochemical pathway in the organic world, since nearly all life depends on it. The very fact that humans get abundant oxygen to breathe is because of photosynthesis, also amplifies the importance of this process. As an interesting bit of trivia regarding the process, the first photosynthetic organisms probably evolved about 3,500 million years ago, early in the evolutionary history of life, when all forms of life on Earth were microorganisms and the atmosphere had much more carbon dioxide.

What is the Photosynthesis Equation?

Photosynthesis is the process by which plants use the energy from sunlight to produce sugar, which in simpler words is the 'fuel' used by all living things. The photosynthesis equation is a chemical representation of the process of photosynthesis which takes place in the chloroplasts. Plants take in carbon dioxide and water to produce glucose (a sugar) and oxygen. The following is the chemical equation, that expalins this process:

Carbon dioxide + water produces -> glucose + oxygen

In chemical language, this is written as,
6CO­2 + 6H2O produces -> C6H12O6 + 6O2

The above chemical equation is read as,
Six molecules of carbon dioxide plus six molecules of water, produce one molecule of sugar and six molecules of oxygen.

What does the Equation mean:

Photosynthesis occurs in two stages. In the first stage, light-dependent reactions capture energy of light and use it to make the energy-storage molecules called ATP and NADPH. During the second stage, the reactions then use these products to capture and reduce carbon dioxide.

The Products of Photosynthesis:

The final product of photosynthesis which is glucose is stored in the complex molecular structure of the plant cells. Oxygen produced as a byproduct is released to the surrounding which is used in respiration by living organisms. In addition to oxygen supply, the glucose synthesized by means of photosynthesis is source of energy for living organisms and is circulated in the food chain. Thus, plants are crucial for balancing the atmospheric air composition and supporting the aerobic ecosystem in every way.

It is interesting to notice that when we burn wood, we’re basically reversing the chemical formulae of photosynthesis that was just explained. The carbohydrate is breaks down and carbon dioxide gas, water and energy are produced. In a more real sense, first sunlight is captured in the carbohydrate, which is then stored in the plant for a while. When the process of burning starts, the sunlight's energy would be released again.
Photosynthesis:

Imagine a planet with thin amounts of oxygen – in other words there would be no planet at all! All thanks to the process of photosynthesis which allows plants to convert light energy into usable food and remove carbon dioxide from the atmosphere and release oxygen into our environment. Without plants that perform photosynthesis, the oxygen on our planet would run out and all humans would choke in a carbon-dioxide rich atmosphere.

The Photosynthesis Reaction:

Light + 6CO2 + 12H20 --> C6H12O6 + 6O2 + 6H20

The Photosynthesis Process:

Photosynthesis in plants primarily occurs through its leaves, which are the solar collectors that begin the photosynthetic process. Leaves are covered with a waxy substance called a cuticle that allows them to retain water. Holes called stoma allow carbon dioxide to enter and oxygen to escape. Xylem cells inside the vein transport water from the roots to the leaves so photosynthesis can take place. Photosynthesis fundamentally requires carbon dioxide, which is obtained through tiny pores in plant leaves called stomata. Just like humans breathe through their lungs, plants breathe through their stomata. Oxygen is also released through the stomata and water is obtained by the plant through the roots and delivered to the leaves through vascular plant tissue systems. Sunlight is absorbed by chlorophyll, a green pigment located in plant cell structures called chloroplasts. Chloroplasts are the sites of photosynthesis. 

Within the leaves are mesophyll cells which contain chloroplasts. Photosynthesis occurs within these structures, which contain a substance called chlorophyll. Chlorophyll, along with other pigments present in the chloroplast, absorbs the light energy of all colors but green for use in the photosynthesis process. The remaining green light is reflected back off of the plant, resulting in green color characteristic of a plant using photosynthesis for energy. Then hydrogen and oxygen are produced as by products of the process, by converting water using the energy derived from the sun. The hydrogen is combined with carbon dioxide in order to make food for the plant, whilst oxygen is let out by the plant through its stomates. Some of the light energy gathered by chlorophylls is stored in the form of ATP, or adenosine triphosphate, in order to be used in the next phase of photosynthesis. 

During the final stage of photosynthesis, which is considered to be light-independent, carbon dioxide is converted into glucose. This chemical change requires the ATP that was stored in the first part of the photosynthesis cycle. This combination creates a compound called glyceraldehyde 3-phosphate, which combines with another glyceraldehyde 3-phosphate compound as it is produced, to produce one glucose molecule. 

This wonderful process continuously happens during the day whilst we go about our everyday activities. If it weren’t for the process of photosynthesis, of what use would be all the precious solar energy that the sun provides us with?

Photosynthesis and Energy

The primary product of Photosynthesis is Glucose along with other products such as fats, proteins and water soluble sugars such as maltose and sucrose. All the living creatures on the earth depend on fats, proteins and carbohydrates to derive their basic source of energy and thus have a direct dependence on the process of Photosynthesis for their survival.

Photosynthesis and Respiration:

Whilst Photosynthesis requires carbon dioxide and releases oxygen to produce glucose, respiration needs oxygen while inhaling and releases carbon dioxide while exhaling. Photosynthesis happens during the day time when the sun shines because the plants require sunlight to produce energy and respiration happens continuously. But unlike other living creatures plants breathe once in a day. During night, when there is no sunlight, stomata are closed and the leaves breathe releasing carbon dioxide in the air. 

The level of carbon dioxide in the environment largely depends on the process of Photosynthesis. Industries and excessive number of vehicles on the road and other hazards of the modern era have led to increasing use of fuel and release of industrial waste and carbon monoxide which is critically fatal for our environment.

Interestingly, just as the increase in the carbon-dioxide level may harm the environment; similarly decrease in the level may cause the planet to freeze as carbon dioxide helps in keeping our planet warm and liveable. Photosynthesis helps in maintaining the balance in both situations.

Photosynthesis is also the prime process that runs the entire food chain and thus forms the base of the food pyramid. Green plants, the producers of the food pyramid, depend on this process. Photosynthesis can be defined as, Synthesis of compounds with the aid of radiant energy. The process of Photosynthesis allows green plants to produce food and energy they require, all on their own. Hence making them an autotrophic breed i.e. they are self-dependent for food. 

Other than these green plants, some protists (algae) and bacteria also use the photosynthesis process to feed, survive and grow. The ones who fail to produce their own food are called heterotrophs. All the other living beings, therefore, are in some way or the other eventually dependent on these autotrophs. The animals who feed on these trees and plants for their living, hence directly depending on them, are called the primary consumers of the food chain. These animals are the herbivores (plant-eaters), who form the source of food for the secondary consumers of food pyramid, the carnivores and the omnivores. The carnivores are the animals who eat only meat, while omnivores are the ones who eat both meat and plants for food. And similarly the food chain continues, making it clearly evident that the process of photosynthesis is the basic source of food and energy in our ecosystem.

Importance of Photosynthesis

Photosynthesis is a crucial energy-converting process by which plants produce molecular oxygen and carbohydrates by the use of photons present in the light. The natural source of light, the sun, helps the green colored plants to fix the atmospheric carbon dioxide in to usable molecular oxygen, that we humans happen to breathe. 

They help in maintaining a balanced level of oxygen and carbon dioxide in the atmosphere. Almost all the oxygen present in the atmosphere can be attributed to the process of photosynthesis, which also means that respiration and photosynthesis go together. Also, the chemical energy stored in plants is transferred to animal and humans when they consume plant matter. Photosynthesis can therefore be considered the ultimate source of life for nearly all plants and animals by providing the source of energy that drives all their metabolic processes.


In a nutshell, the process of photosynthesis benefits us in the following ways:

1. Photosynthesis converts inorganic raw materials into food, that provides our ecosystem with energy. 
2. Green plants provide organic food to all the animals and humans. 
3. Rare fossil fuels like coal, petroleum and natural gas are formed through the degradation of the past plant and animal parts, which were originally formed by photosynthesis. 
4. Plant products like timber, rubber, herbs, medicines resin and oils are derived from photosynthesis. 
5. Photosynthesis helps in providing oxygen in the atmosphere required by all living organisms. 
6. Photosynthesis decreases the concentration of carbon dioxide and other harmful industrial wastes that lead to respiration problems in living beings.