How plants turn sunlight, water, and air into food — and oxygen for us to breathe.
Photosynthesis is the process by which green plants, algae, and some bacteria capture light energy and use it to make sugar from carbon dioxide and water. The leftover oxygen is released into the atmosphere — the same oxygen we breathe.
A plant needs three things to run photosynthesis: light (usually from the sun), water (pulled up through the roots), and carbon dioxide (absorbed through tiny pores on the leaves called stomata). Inside the leaf, a green pigment called chlorophyll does the actual light-catching.
Which of these is NOT something a plant needs for photosynthesis?
In shorthand: 6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂. Six molecules of carbon dioxide plus six of water, powered by light, give one molecule of glucose (sugar) and six of oxygen. The plant uses the glucose for energy and growth, and releases the oxygen as a byproduct.
Inside plant cells are tiny green compartments called chloroplasts. Each chloroplast is packed with chlorophyll, the pigment that absorbs red and blue light — and reflects green, which is why leaves look green to us.
Why do most leaves appear green?
The light-dependent reactions happen in the thylakoid membranes and split water to release oxygen. The light-independent reactions (the Calvin cycle) happen in the stroma and use the captured energy to build sugar from CO₂. Stage one captures energy; stage two assembles food.
Where does the oxygen released by photosynthesis come from?
Photosynthesis is the foundation of almost every food chain on Earth. It also produces the oxygen that animals — including us — need to breathe, and it removes carbon dioxide from the atmosphere, helping regulate the climate.