Final answer:
Carbon dioxide is fixed during the Calvin cycle or light-independent reactions of photosynthesis, not the light-dependent reactions. These occur in the chloroplast stroma and use energy from ATP and NADPH produced by light-dependent reactions.
Step-by-step explanation:
It is false that CO₂ fixation happens in the light-dependent reactions of photosynthesis. Carbon dioxide is actually fixed during the light-independent reactions, which are also known as the Calvin cycle. In the chloroplast stroma, CO₂ is converted into organic compounds through a series of reactions that are not directly driven by light, although they require the chemical energy (ATP and NADPH) produced during the light-dependent reactions.
During the Calvin cycle, CO₂ from the air enters a plant's leaves through stomata and diffuses into the mesophyll cells, reaching the chloroplast stroma. There, three main stages occur: carbon fixation, reduction, and regeneration, leading to the synthesis of glucose and other carbohydrates. While these reactions are termed 'light-independent' because light isn't directly involved, they are intimately connected to the light-dependent reactions, relying on their products to proceed.