Here's why:
* Photosynthesis requires energy: The overall reaction converts carbon dioxide and water into glucose and oxygen, a process that requires energy. This energy is supplied by sunlight.
* Endergonic reaction: Photosynthesis is an endergonic reaction, meaning it absorbs energy from its surroundings.
* ΔG value: The standard Gibbs free energy change for photosynthesis is approximately +2880 kJ/mol.
However, it's crucial to understand that:
* Photosynthesis is a complex process: It involves multiple steps, and the overall ΔG is a combination of the ΔG values for each step. Some individual steps are exergonic (release energy) while others are endergonic.
* Sunlight provides the energy: Photosynthesis uses light energy to drive the endergonic reactions, making the overall process possible.
Therefore, while the ΔG for photosynthesis is positive, it's not accurate to say it's simply "non-spontaneous." It's more accurate to say it's an endergonic reaction that is driven by sunlight.
