Photosynthesis is the most fundamental process in nature. All life on earth depends directly or indirectly on this process. The present state of our knowledge regarding the photosynthetic process proves that it is not a one step process, but it is a two step process.
The primary reaction in photosynthesis depends on light and hence called light reaction or photochemical reaction. The light reaction is followed by second step in which light is not required but the product of light reaction is used up for the fixation of carbon dioxide in carbohydrates, known as dark reaction or thermochemical reaction.
The light reaction is initiated when specific light is absorbed by antenna chlorophyll. The absorbed energy is either trapped at the reaction centre and used to perform photo-chemical act. The two photosystems are known as photosystem I and photosystem II. both exist as structural entities within the thylakoid lamellae forming separate pigment protein complexes.
The process of photosynthesis involves the plant using chloroplasts to catch sun light's energy and combine carbon dioxide with it to make food. The process occurs where a light source exists. Therefore, plant life in the oceans occurs more towards the upper part of the ocean where light can reach the plants.
Photosynthesis occurs in two specific stages. The first step occurs as the light is absorbed and a carbon fixation cycle starts. After the molecules in a plant become alerted by the sunlight the energy is absorbed. It then breaks down water molecules. Electrons move away and they go through a process called Oxidative phosphorylation. An ATP molecule is produced. The electrons become active once again in the photo system and produce the molecule NADPH which is used to create carbon dioxide.
The second cycle is called the Calvin cycle. It takes place in the stroma of the chloroplasts. Sunlight is not needed during this process. Carbon molecules are changed into sugar as the systems and molecules react to one another.
"6CO2 + 12H2O + sunlight -> C6H12O6 + 6H2O + 6O2"