Final answer:
The Calvin cycle is a series of chemical reactions that occur in the stroma of chloroplasts during photosynthesis. It uses ATP and NADPH from light reactions to fix carbon dioxide and produce high-energy molecules like Glyceraldehyde-3-phosphate, culminating in the synthesis of glucose while regenerating RuBP.
Step-by-step explanation:
Understanding the Calvin Cycle
The Calvin cycle is a crucial part of the light-independent reactions of photosynthesis, taking place in the stroma of chloroplasts. It involves three basic stages: carbon fixation, reduction, and regeneration of the starting molecule Ribulose bisphosphate (RuBP). During the cycle, ATP and NADPH, which were produced in the light reactions, provide the energy necessary to assimilate carbon dioxide (CO2) and produce high-energy molecules. Specifically, for every three turns of the cycle, six molecules of 3-phosphoglycerate (3-PGA) are produced in the fixation stage. Then, in the reduction stage, ATP and NADPH are used to convert these to Glyceraldehyde-3-phosphate (GA3P), a high-energy molecule. It is important to note that nine molecules of ATP and six molecules of NADPH are used for every three turns of the cycle. Finally, the cycle uses additional ATP to regenerate RuBP, enabling the cycle to continue.
Six turns of the Calvin cycle yield one glucose molecule, which necessitates the consumption of 12 ATP and 12 NADPH in the reduction phase and an additional six ATP in the regeneration phase. This contrasts with the Krebs cycle, which is a part of cellular respiration and functions to generate ATP and NADH.