In photosynthesis, the light-independent reactions of the Calvin cycle are driven by inputs of _ and _ from the light dependent reactions. A. NADPH B. NADH C. Oxygen D. ATP E. CO2
The Correct Answer and Explanation is:
Correct answer: A. NADPH and D. ATP
In photosynthesis, the Calvin cycle is the series of light-independent reactions that take place in the stroma of the chloroplast. These reactions do not require light directly, but they depend on the products of the light-dependent reactions, which occur in the thylakoid membranes.
The light-dependent reactions use sunlight to split water molecules, releasing oxygen as a byproduct and generating two crucial energy-rich molecules: ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate). These molecules carry the energy and high-energy electrons required to power the Calvin cycle.
During the Calvin cycle, carbon dioxide (CO₂) from the atmosphere is captured and used to build organic molecules like glucose. However, carbon dioxide alone is not enough to drive the reactions. The cycle needs energy and reducing power to convert carbon dioxide into three-carbon sugars. That energy comes from ATP, while the reducing power, which supplies electrons for reducing carbon, comes from NADPH.
ATP provides the chemical energy needed to power the formation of bonds in sugar molecules. NADPH donates high-energy electrons to help convert the three-carbon molecules into more complex carbohydrates.
Thus, even though light is not directly used during the Calvin cycle, it is essential for creating ATP and NADPH in the earlier stage. Without these molecules, the Calvin cycle would not function.
The incorrect choices are:
- B. NADH, which is involved in cellular respiration, not photosynthesis.
- C. Oxygen, which is a byproduct of light-dependent reactions, not an input for the Calvin cycle.
- E. CO₂ is required for the Calvin cycle but does not come from the light-dependent reactions.
So the correct inputs from the light-dependent reactions that drive the Calvin cycle are ATP and NADPH.
