The Calvin Cycle is a crucial process in photosynthesis, where carbon dioxide is converted into glucose. Here’s a breakdown of each step of the cycle:
Diagram of the Calvin Cycle
Below are the primary steps of the Calvin Cycle:
1. Carbon Fixation
During this initial phase, carbon dioxide from the atmosphere is incorporated into a five-carbon sugar molecule called ribulose bisphosphate (RuBP). This reaction is facilitated by the enzyme ribulose bisphosphate carboxylase/oxygenase (RuBisCO). The resulting six-carbon compound is unstable and splits into two three-carbon molecules called 3-phosphoglycerate (3-PGA).
2. Reduction Phase
In the second step, the 3-PGA molecules undergo phosphorylation by ATP and reduction by NADPH (both derived from the light reactions of photosynthesis) to form glyceraldehyde-3-phosphate (G3P). G3P is a sugar that can be used to form glucose and other carbohydrates.
3. Regeneration of RuBP
In the final phase, some of the G3P molecules go on to form glucose, while others are used to regenerate RuBP, allowing the cycle to continue. This regeneration requires ATP and ensures that RuBP is reformed to keep the cycle running.
Overall, the Calvin Cycle is essential for synthesizing glucose and other organic compounds in plants. Each step plays a vital role in the transformation of inorganic carbon into a usable form for energy and growth.