Which intermediate is formed in Stage 2 of the Calvin Cycle before glyceraldehyde 3-phosphate?

In the Calvin Cycle, the process begins with carbon fixation, where carbon dioxide is incorporated into an organic molecule. The first stages involve converting ribulose 1,5-bisphosphate into 3-phosphoglycerate.

Following this, stage 2 of the Calvin Cycle involves the conversion of 3-phosphoglycerate into an intermediate known as 1,3-bisphosphoglycerate. This conversion occurs through the action of the enzyme phosphoglycerate kinase, which uses ATP to phosphorylate 3-phosphoglycerate. The resulting 1,3-bisphosphoglycerate is then further processed in subsequent steps, which ultimately lead to the production of glyceraldehyde 3-phosphate.

The selection of 1,3-bisphosphoglycerate as the correct intermediate is critical, as it is directly involved in the progression of the Calvin Cycle towards synthesizing carbohydrates during the process of photosynthesis. Understanding the order of intermediates is essential, as it highlights the transformation of energy and carbon sources into usable carbohydrates for the plant's metabolic processes.