The light-dependent reactions of photosynthesis take place in the thylakoid membranes of chloroplasts and require light energy to synthesize ATP and NADPH. In contrast, the light-independent reactions, commonly referred to as the Calvin cycle, occur in the stroma of chloroplasts. These reactions utilize the ATP and NADPH generated during the light-dependent phase to convert carbon dioxide into glucose.

During the light-dependent reactions, light energy is absorbed by pigments, primarily chlorophyll, and is converted into chemical energy in the forms of ATP and NADPH. This conversion is known as photophosphorylation and involves the transfer of electrons through the electron transport chain. Additionally, water molecules are split during this process, resulting in the release of oxygen as a by-product.

On the other hand, light-independent reactions do not require light energy; instead, they utilize the ATP and NADPH produced in the light-dependent reactions to fix carbon dioxide into glucose. This process, referred to as carbon fixation, consists of a series of enzyme-catalyzed reactions that transform carbon dioxide into organic compounds. The initial step involves the fixation of carbon dioxide into a three-carbon molecule called 3-phosphoglycerate, which is subsequently converted into glucose.

In summary, both light-dependent and light-independent reactions are crucial for the process of photosynthesis. The light-dependent reactions generate the ATP and NADPH necessary for carbon fixation in the light-independent reactions, which ultimately produce the glucose essential for plant growth and metabolism.