Photosynthesis is the remarkable process by which plants capture light energy from the sun and use it to convert carbon

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Photosynthesis is the remarkable process by which plants capture light energy from the sun and use it to convert carbon dioxide and water into energy-rich sugars while releasing oxygen as a byproduct. The overall chemical equation for this process is 6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂. It occurs within specialized organelles called chloroplasts, primarily in the leaves of green plants.

The process unfolds in two interconnected stages that work together seamlessly. In the light-dependent reactions, which take place in the thylakoid membranes inside the chloroplasts, chlorophyll and other pigments absorb sunlight. This absorbed energy splits water molecules through photolysis, releasing oxygen gas, protons, and electrons. The energy is then converted into chemical forms—specifically ATP and NADPH—through an electron transport chain that creates a proton gradient for ATP synthesis. These energy carriers store the captured light energy and provide the power needed for the next stage.

The light-independent reactions, also known as the Calvin cycle, occur in the surrounding stroma of the chloroplast. Here, the ATP and NADPH produced in the first stage drive the fixation of carbon dioxide into three-carbon sugars such as glyceraldehyde-3-phosphate (G3P). Through a series of enzymatic steps, these molecules are assembled into glucose and other carbohydrates that the plant uses for energy storage and growth. Although this stage does not directly require light, it depends entirely on the products of the light-dependent reactions, and some of its enzymes are activated by light.

By transforming sunlight into chemical energy, photosynthesis forms the foundation of most food chains on Earth. It supplies the oxygen we breathe and the organic compounds that sustain plants and the animals that rely on them, making it essential for life as we know it.