# Photosynthesis: A Comprehensive Overview

## What It Is
Photosynthesis is the process by which organisms convert light energy into chemical energy, storing it in glucose and other organic compounds.

## The Basic Equation
**6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂**

## Where It Occurs
- **Chloroplasts** in plant cells
- Specifically in the **thylakoid membranes** (light reactions) and **stroma** (Calvin cycle)

## The Two Main Stages

### 1. Light-Dependent Reactions
- Occur in thylakoid membranes
- Chlorophyll absorbs light (mainly red and blue wavelengths)
- Water is split, releasing O₂
- Produce ATP and NADPH
- Involve Photosystems I and II, electron transport chain

### 2. Light-Independent Reactions (Calvin Cycle)
- Occur in the stroma
- Use ATP and NADPH from light reactions
- Fix CO₂ into glucose via enzyme RuBisCO
- Three phases: carbon fixation, reduction, regeneration

## Variations
- **C3 photosynthesis**: Most plants; direct Calvin cycle
- **C4 photosynthesis**: Corn, sugarcane; spatial separation
- **CAM photosynthesis**: Cacti, succulents; temporal separation (night CO₂ uptake)

## Global Importance
- Produces atmospheric oxygen
- Foundation of most food chains
- Carbon sequestration

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