1. Capturing Light Energy:
* Chloroplasts: The process begins in chloroplasts, the green organelles within plant cells. These contain chlorophyll, a green pigment that absorbs sunlight.
* Light-Dependent Reactions: Sunlight energy is captured by chlorophyll and used to split water molecules (H₂O). This process releases oxygen (O₂) as a byproduct and generates energy carriers called ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).
2. Building Sugars:
* Calvin Cycle (Light-Independent Reactions): The energy carriers (ATP and NADPH) from the light-dependent reactions power the Calvin cycle, which takes place in the stroma (the fluid within the chloroplast).
* Carbon Dioxide Fixation: Carbon dioxide (CO₂) from the air is absorbed by the plant through tiny pores called stomata and incorporated into an organic molecule called RuBP (ribulose bisphosphate).
* Sugar Production: A series of chemical reactions convert RuBP into glucose (a simple sugar) using the energy from ATP and NADPH. This glucose is the plant's food source and can be used for growth, reproduction, or stored for later use.
Summary:
Photosynthesis is a two-step process that converts light energy into chemical energy stored in glucose:
1. Light-Dependent Reactions: Capture light energy, split water, and produce ATP and NADPH.
2. Calvin Cycle: Uses ATP and NADPH to convert carbon dioxide into glucose.
Key Products of Photosynthesis:
* Glucose (C₆H₁₂O₆): The plant's food source.
* Oxygen (O₂): A byproduct released into the atmosphere.
Overall Equation:
6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂
(Carbon Dioxide + Water + Light Energy → Glucose + Oxygen)
