Dark Phase and Light Phase in the Process of Photosynthesis

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll present in their leaves. It is a complex process that consists of two main phases: the light phase and the dark phase. In this article, we will discuss the dark phase and light phase in the process of photosynthesis.

The Light Phase

The light phase is the first phase of photosynthesis, also known as the light-dependent reaction. It is called so because it requires light energy to occur. During this phase, the chlorophyll present in the chloroplasts of the plant cell absorbs the light energy from the sun and converts it into chemical energy in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate). The light phase takes place in the thylakoid membranes of the chloroplasts.

The light phase can be further divided into two stages:

1. Photophosphorylation: In this stage, the light energy absorbed by the chlorophyll is used to generate ATP. ATP is a high-energy molecule that stores the energy required for the dark phase of photosynthesis.

2. Photolysis: In this stage, water molecules are broken down into oxygen, hydrogen ions, and electrons. The oxygen is given off as a by-product, while the hydrogen ions and electrons are used to produce NADPH, another energy molecule.

The Dark Phase

The dark phase is the second phase of photosynthesis, also known as the light-independent reaction or the Calvin cycle. It is called so because it does not require light energy to occur. During this phase, the ATP and NADPH generated in the light phase are used to produce glucose, which is the primary food source for the plant. The dark phase occurs in the stroma of the chloroplasts.

The dark phase can be divided into three stages:

1. Carbon Fixation: In this stage, carbon dioxide (CO2) is fixed into a stable organic molecule called ribulose bisphosphate (RuBP) with the help of the enzyme RuBisCO.

2. Reduction: In this stage, ATP and NADPH generated in the light phase are used to convert the unstable RuBP molecule into a stable three-carbon sugar molecule called glyceraldehyde-3-phosphate (G3P).

3. Regeneration: In this stage, the remaining RuBP molecules are regenerated with the help of ATP generated in the light phase, in order to continue the cycle.

Conclusion

In conclusion, the process of photosynthesis is a complex process that consists of two main phases: the light phase and the dark phase. The light phase requires light energy to occur, and it generates ATP and NADPH. The dark phase does not require light energy and uses the ATP and NADPH generated in the light phase to produce glucose, the primary food source for the plant.

the reactions which occur during day in the presence of sunlight is called light phase and the reactions which occurs during tha night in the absence of sunlight is called dark phase...light phase occurs in grana and dark phase occurs in stroma...