ABCTE Biology Practice Exam

The dark reactions of photosynthesis, more commonly known as the Calvin cycle, are primarily responsible for synthesizing glucose from carbon dioxide and water using the energy generated during the light-dependent reactions. This process occurs in the stroma of chloroplasts and does not require light directly, although it relies on the ATP and NADPH produced in the light-dependent reactions.

During the Calvin cycle, carbon dioxide is fixed into an organic molecule in a series of enzymatic reactions, ultimately leading to the production of glucose. This glucose can then be utilized by the plant for energy or converted into starch for storage.

The other molecules listed, such as oxygen and water, are not produced during the dark reactions; instead, oxygen is released as a byproduct in the light-dependent reactions when water is split to provide electrons. ATP, while important in providing energy for the Calvin cycle, is produced during the light-dependent reactions and is not a direct product of the dark reactions.

In summary, the production of glucose during the dark reactions signifies the culmination of carbon fixation and energy utilization, marking it as the primary output of the Calvin cycle.