What is Photosynthesis?

See the Photosynthesis Diagram and know more about the process of Photosynthesis.

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.