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Plants are multicellular, eukaryotic organisms that are identified by their ability to make their own food. The ability of plants to make their own food calls them autotrophic organisms.

 Several algae, bacteria and phytoplanktons are also autotrophic in nature.Plants cook their food by the process known as photosynthesis. Photosynthesis is the phenomenon of converting light energy into chemical energy. The plants trap the light energy and convert carbon dioxide, water and minerals into oxygen and energy-rich carbohydrates. 

Photosynthesis: Process 

The reaction of photosynthesis can be depicted by the following equation:

6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O

The process of photosynthesis takes place in two stages. Let us look at those stages in detail:

Light Dependent Reaction

The light dependent reaction, as the name suggests, takes place in the presence of light. It takes place in the thylakoid membrane of the chloroplast. At this stage, the chlorophyll pigments in the chloroplast trap the light energy to convert it into energy molecules of ATP and NADPH. 

The conversion takes place in two photosystems that are embedded in the thylakoid membrane. The two photosystems are photosystem II (PSII) and photosystem I (PSI). The two photosystems are composed of light-harvesting complexes (LHC) and reaction centres with chlorophyll molecules. 

The energy molecules, also called energy carriers, help in moving the energy from light dependent reaction to light independent reaction. After draining their energy, these molecules return to get energised again. 

Light Independent Reaction 

The light independent reaction, also known as dark reaction, does not necessarily need the presence of light to carry out reactions. However, they do need energy carriers from the light dependent reaction to start their process. 

The light independent reaction was discovered by Melvin Calvin, James Bassham, and Andrew Benson in 1950 and is sometimes also referred to as Calvin–Benson–Bassham (CBB) cycle. It is a cyclical process that involves fixing the carbon dioxide with the energy derived from energy carriers into carbohydrates. 

Carbon Fixation

Carbon is an essential component that comprises all organic compounds on Earth. The main source of carbon is carbon dioxide from the living organisms and dissolved amounts in air and water. The autotrophs such as plants and algae carry out photosynthesis to fix the carbon dioxide and convert it into simpler forms of carbohydrates.

The simple carbohydrates can then be consumed by the producers to start an energy chain. This whole circle of carbon from one source to another is referred to as the carbon cycle. Another form of the carbon cycle is when the plants and animals die; they are buried into the soil, where they convert into fossil fuel after several years. This fossil fuel is burnt in the form of coal and petroleum to release the carbon dioxide back into the atmosphere. Visit BYJU’S Biology to learn more about plants and their relationship with carbon. Students can also learn more by watching different subject related YouTube videos by subscribing to YouTube videos.