As most definitions go, the meaning of the word literally translates to its function. Breaking down the word “autotrophic”, we get “auto”, as in self and “troph” meaning nutrition. Piecing it together means organisms, which make their own food. Photosynthesis, as has been discussed before is the process by which green plants, that are autotrophic in nature synthesize their own food. Plants and animals do not obtain food in the same way. Hence there is autotrophic nutrition and heterotrophic nutrition.
We are well aware that chlorophyll (the green pigment), light and carbon dioxide are necessary for photosynthesis to occur. Discussing further in detail:
• Chlorophyll: It is the green pigment present in plants that facilitate photosynthesis. This green color is generally present on the leaves of plants. Furthermore, stems and fruits may also possess this green color, in some organisms like algae, the whole plant in itself is green and takes part in photosynthesis.
• Carbon Dioxide: CO2 is present in a very small amount in the atmosphere; this carbon dioxide is absorbed by terrestrial plants, while aquatic ones make do with carbon dioxide dissolved in water. CO2 is absorbed through the stomata present on the surface of leaves. They are tiny pores that open and close.
• Sunlight: Ultimately all forms of life on earth rely on sunlight for energy. In autotrophic plants, light is used for splitting water molecules into hydrogen and oxygen and it is given the name of photolysis.
Photosynthesis is divided into two parts:
• Light-dependent reaction (Light reactions): They need light to produce organic energy molecules (ATP and NADPH). They are initiated by the green pigment mostly.
• Light-independent reactions (Dark reactions): They make use of these organic energy molecules that were produced previously. It is also called the Calvin Benison cycle, and it occurs in the stroma. Where NADHP provides electrons required to fix carbon dioxide into carbohydrates and ATP provides the energy.
To summarize the process, light is absorbed by the green plants, at the site of chlorophyll. This absorbed energy as discussed above results in the splitting of water molecules into hydrogen and oxygen. And during this process, light energy gets converted into chemical energy. Carbon dioxide and water are taken in by organisms and used to synthesize glucose, which can be broken down later during respiration to release the energy needed for life. Finally, carbon dioxide gets reduced to carbohydrate.
This is a brief description of photosynthesis as a means of autotrophic nutrition. To learn more download Byju’s- The Learning App.