Advanced Placement (AP) Biology Practice Exam

What is the primary function of light-independent reactions?

1. Convert light energy into chemical energy

2. Use ATP and NADPH to synthesize glucose

3. Produce oxygen as a byproduct

4. Initiate the electron transport chain

The correct answer is: Use ATP and NADPH to synthesize glucose

The primary function of light-independent reactions, commonly referred to as the Calvin cycle, is to utilize the ATP and NADPH generated during the light-dependent reactions to synthesize glucose from carbon dioxide. This process takes place in the stroma of chloroplasts and does not directly require light, hence the term "light-independent." During this cycle, carbon fixation occurs, which involves capturing carbon dioxide and converting it into a simple sugar, ultimately leading to the formation of glucose. The ATP provides the energy required for these reactions, while NADPH supplies the reducing power needed to transform carbon compounds into carbohydrates. This essential process allows plants to create energy-rich molecules that serve as a fundamental energy source for growth and metabolism.