Advanced Placement (AP) Biology 2025 – 400 Free Practice Questions to Pass the Exam

The process that involves light-independent reactions in photosynthesis is the Calvin Cycle. This cycle occurs in the stroma of the chloroplasts and is responsible for converting carbon dioxide and other compounds into glucose, using the energy stored in ATP and NADPH produced during the light-dependent reactions.

In the Calvin Cycle, carbon fixation occurs as CO2 is incorporated into an existing organic molecule, followed by a series of reduction and regeneration processes. This cycle does not directly require light; instead, it relies on the products generated in the light-dependent reactions, which harness light energy to produce ATP and NADPH.

Other processes such as the electron transport chain are solely part of the light-dependent reactions in photosynthesis, where light energy is converted into chemical energy. The Krebs cycle, also known as the citric acid cycle, occurs in cellular respiration and is not directly related to photosynthesis. Similarly, fermentation is an anaerobic process that generates energy without the use of oxygen and is unrelated to photosynthesis. Therefore, the Calvin Cycle is the only answer that properly identifies a light-independent process within the broader context of photosynthesis.