Which provides the energy carrier for the dark stage to proceed?

Which provides the energy carrier for the dark stage to proceed?

• A. Water
• B. Light energy
• C. ATP from the light stage
• D. Heat

Answer: (C)

The energy needed for the dark stage is provided in the form of ATP produced during the light reactions. The Calvin cycle uses ATP to drive the energy-demanding steps that convert carbon dioxide into sugars, while NADPH provides the reducing power. Water is the source of electrons in the light reactions, not the energy carrier for the dark stage. Light energy is the initial energy input, but it is converted into chemical energy stored as ATP (and NADPH); the step that actually powers the dark stage is ATP. Heat doesn’t play a role in driving these biochemical reactions. So ATP from the light stage is the energy carrier that enables the dark stage to proceed.

The energy needed for the dark stage is provided in the form of ATP produced during the light reactions. The Calvin cycle uses ATP to drive the energy-demanding steps that convert carbon dioxide into sugars, while NADPH provides the reducing power. Water is the source of electrons in the light reactions, not the energy carrier for the dark stage. Light energy is the initial energy input, but it is converted into chemical energy stored as ATP (and NADPH); the step that actually powers the dark stage is ATP. Heat doesn’t play a role in driving these biochemical reactions. So ATP from the light stage is the energy carrier that enables the dark stage to proceed.