Hello aspirant,

I also had this doubt while studying photosynthesis in Biology. From what I learned, the light-dependent reaction must occur before the light-independent reaction because it produces the energy molecules required for the next stage.

In the light-dependent reactions, sunlight is absorbed by chlorophyll in the chloroplasts. This process generates ATP and NADPH, which store energy. These molecules are essential for the light-independent reaction (Calvin cycle).

The light-independent reaction uses the ATP and NADPH produced earlier to convert carbon dioxide into glucose. If the light-dependent reaction does not occur first, ATP and NADPH will not be available, and the Calvin cycle cannot proceed. Therefore, the light-dependent reaction must occur before the light-independent reaction.

For better understanding, I found some helpful Careers360 resources that explain photosynthesis and important Biology concepts for students:

• Photosynthesis – Process and Steps
https://school.careers360.com/articles/photosynthesis

• Biology Study Material and Concepts
https://school.careers360.com/biology

• Previous Year Question Papers and Preparation Resources
https://school.careers360.com/articles/previous-year-question-papers

These resources helped me understand the concept clearly while preparing for exams.

Hope this helps.

Thank you.