Photosynthesis is the process through which plants (and some other organisms), covert light energy from the sun into chemical energy that can be utilized by other organisms. In order to carry out this complex process, cells are equip with specialized cells. There is a cell wall made of cellulose, within, there are membrane closed organelles, and in addition, there is another specialized organelle called a chloroplast. The chloroplast is the feature of the plant cell that allows the plant to carry out photosynthesis.
In photosynthesis, there are two major stages, the first being light-dependent reactions and the other being the Calvin cycle, both take place within the chloroplast. The light dependent reactions occur before the Calvin cycle takes place. While the Calvin cycle is not actually part of the light-dependent reactions of photosynthesis, the Calvin cycle does indirectly depend on light.
The light-dependent reactions, as stated above, occur prior to the Calvin cycle. The Calvin cycle actually requires the use of the products from the light dependent reactions. Products include ATP (adenosine triphosphate), NADPH (nicotinamide adenine dinucleotide phosphate-oxidase), and also o2 that is released into the atmosphere. There are energy and material requirements of the Calvin cycle, which rely on light-dependent reactions as their suppliers.
There are 3 phases of the Calvin cycle: carbon fixation, reduction, regeneration of co2 acceptor. With all three phases, there is an overall “cost” of the Calvin cycle. The Calvin cycle needs outside resources, these resources are produced by the light-dependent reactions. These “costs” of resources include, 3 co2, 9 ATP, and 6 NADPH. Co2 comes from the atmosphere, however, without light-dependent reactions, the Calvin cycle has no way to obtain the required ATP and NADPH.
The Calvin cycle is indirectly dependent on light because without the light-dependent reactions, and their products, the Calvin cycle cannot take place.