What are the energy sources for the Calvin cycle?

The energy sources for the Calvin cycle are ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).

The Calvin cycle, also known as the light-independent reactions or the dark phase of photosynthesis, is the process by which plants convert carbon dioxide into glucose. This process requires energy, which is supplied by ATP and NADPH. These two molecules are produced in the light-dependent reactions of photosynthesis, which occur in the thylakoid membranes of the chloroplasts.

ATP, or adenosine triphosphate, is often referred to as the 'energy currency' of the cell. It is a high-energy molecule that stores and transports chemical energy within cells. In the Calvin cycle, ATP provides the energy needed for the conversion of 3-PGA (3-phosphoglycerate) to 1,3-BPG (1,3-bisphosphoglycerate), a key step in the synthesis of glucose.

NADPH, or nicotinamide adenine dinucleotide phosphate, is another crucial molecule in the Calvin cycle. It acts as a reducing agent, donating electrons to help convert 1,3-BPG to G3P (glyceraldehyde 3-phosphate), the molecule that is eventually used to form glucose. The NADPH used in the Calvin cycle is generated in the light-dependent reactions, where it is formed as water is split and electrons are transferred along a series of proteins.

In summary, the Calvin cycle relies on ATP for energy and NADPH for reducing power. Both of these molecules are produced in the light-dependent reactions of photosynthesis, linking the energy of sunlight to the synthesis of glucose. This process is fundamental to life on Earth, as it provides the energy that fuels the growth and metabolism of plants, and indirectly, of all organisms that rely on plants for food.