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# Notes on Photosynthesis The notes describe the process of photosynthesis, focusing on the light-dependent and light-independent reactions. ## Light-Dependent Reactions * **Chemiosmosis:** ATP is created through a process called chemiosmosis, where protons (H+) move across the thylakoid membra...

# Notes on Photosynthesis The notes describe the process of photosynthesis, focusing on the light-dependent and light-independent reactions. ## Light-Dependent Reactions * **Chemiosmosis:** ATP is created through a process called chemiosmosis, where protons (H+) move across the thylakoid membrane. * **High Proton Concentration:** The movement of protons creates a high concentration inside the thylakoid membrane. * **ATP Production:** As the protons combine with free phosphate, this creates ATP from ADP, a process called photophosphorylation (making ATP using light). * **NADPH:** NADPH is also generated during the light dependent stage, used in the light-independent reactions. ## Light-Independent Reactions (Calvin Cycle) * **Location:** Takes place in the stroma, outside the thylakoid membrane. * **Carbon Fixation:** CO2 molecules are used in a process called carbon fixation, where CO2 combines with a 5-carbon molecule called RuBP, forming an unstable 6-carbon molecule that quickly splits into two 3-PGA molecules. * **Step 2:** The 3-PGA molecules combine with a phosphate from ATP and a H+ from NADPH forming 6 G3P molecules. * **Step 3 & 4:** 5 molecules of G3P are recycled to continue carbon fixation(regenerating RuBP), while 1 molecule of G3P is used to synthesise glucose. **Important molecules:** * ATP: Adenosine triphosphate; carries energy * ADP: Adenosine diphosphate; a lower-energy form of ATP. * NADPH: a high-energy molecule * RuBP: Ribulose-1,5-bisphosphate * CO2: Carbon dioxide * 3-PGA: 3-Phosphoglycerate **Equations (partially visible):** * $ 3-PGA + ATP + NADPH = 6G3P$