Quick Answer
Photosynthesis is the process plants use to convert sunlight into energy. As a byproduct of photosynthesis, plants release oxygen into the air, which makes up about 21% of the air we breathe. So in short, photosynthesis by plants and other organisms provides most of the oxygen that humans and other air-breathing creatures need to survive.
The Photosynthesis Process
Photosynthesis is a complex series of chemical reactions that convert carbon dioxide and water into glucose (sugar) and oxygen, using energy from sunlight. The overall reaction looks like this:
6CO2 + 6H2O + sunlight → C6H12O6 + 6O2
This means six molecules of carbon dioxide (CO2) and six molecules of water (H2O) are converted into one molecule of sugar (C6H12O6) and six molecules of oxygen (O2) using energy from sunlight.
The reactions occur inside chloroplasts, specialized structures found in plant cells, and the cells of other photosynthetic organisms like algae and some bacteria. Inside chloroplasts are stacks of disc-shaped thylakoids containing the green chlorophyll pigment.
When chlorophyll absorbs sunlight, it gains energy from the light. This energy powers the reactions that assemble sugar molecules from carbon dioxide and water. Oxygen is produced as a byproduct and released into the air.
So in summary, photosynthesis uses energy from sunlight to produce sugars for food while releasing oxygen into the air as a waste product. The amount of oxygen produced is proportional to the amount of sugar produced.
Why Photosynthesis Produces Oxygen
Oxygen is produced from photosynthesis because the process splits water molecules. Water (H2O) comprises two hydrogen atoms bonded to an oxygen atom. When water is split during photosynthesis, the hydrogen is used to build sugar molecules, while the oxygen is released as a gas.
For every molecule of sugar produced, six molecules of oxygen are released. The source of both the oxygen and hydrogen atoms that make up the sugar molecules is water. But while the hydrogen is incorporated into sugars, free oxygen atoms accumulate and bubble out as oxygen gas.
The Significance of Photosynthetic Oxygen
The oxygen released from photosynthesis is vital for life on Earth. It makes up about 21% of the gases in the atmosphere. All complex life forms, including humans, require oxygen to power their metabolism. We breathe in oxygen, which reacts with nutrients and fuels in our cells to release energy.
Green plants and other photosynthetic organisms have produced oxygen for over 3.5 billion years. When photosynthesis first evolved, there was very little free oxygen gas on Earth. But as photosynthesis spread, Earth’s atmosphere filled up with oxygen. The development of an oxygen-rich atmosphere made it possible for large, complex creatures like humans to evolve millions of years later.
So in essence, we owe thanks to photosynthesis for making Earth livable! The oxygen it pumps out sustains not just humans but also nearly all complex life on land and in the oceans. Our lives fundamentally depend on the products of this amazing process.
How Much Oxygen Comes From Photosynthesis?
The vast majority of oxygen in Earth’s atmosphere comes from photosynthetic organisms. Scientists estimate that between 70-80% of the oxygen in the air is produced by rainforests alone. Meanwhile, phytoplankton (microscopic marine plants) account for about 50-85% of all photosynthetic activity on Earth.
Other terrestrial plants, from forest trees to lawn grasses, also contribute oxygen. Various photosynthetic organisms produce hundreds of billions of metric tons of oxygen annually.
In contrast, oxygen from non-biological sources makes up less than 1% of total atmospheric oxygen. The small remainder comes from chemical reactions in Earth’s atmosphere and crust. Photosynthesis utterly dominates oxygen production on our planet.
How the Process Developed
Photosynthesis likely originated early in Earth’s history. The earliest life forms were anaerobic, meaning they didn’t require oxygen. Instead, they produced energy via chemical reactions that did not involve oxygen.
But Earth’s atmosphere radically changed when a type of bacteria called cyanobacteria developed the ability to photosynthesize. Cyanobacteria used water as an electron donor, releasing oxygen as a byproduct. As cyanobacteria flourished, oxygen built up in the oceans and atmosphere.
The Future of Photosynthesis
Photosynthesis will continue pumping out oxygen as long as the Sun provides energy. However, some evidence shows the rate of photosynthesis declining in specific ecosystems, like tropical forests.
Deforestation and climate change threaten the natural balance in some areas. But on the whole, photosynthesis is not in danger of stopping anytime soon. If plants receive sufficient light, water, and carbon dioxide, they will keep photosynthesizing at high rates.
The carbon dioxide released by burning fossil fuels increases photosynthesis in some areas. But too much can disrupt natural systems. In the future, striking the right balance is key to maximizing the oxygen benefits from this amazing process.
Why Photosynthesis Matters
Photosynthesis may seem esoteric, but it’s vital for anyone who cares about their health or humanity’s future. The oxygen photosynthesis provides makes complex life possible. And the food it produces sustains both plants and animals.
Plus, advances based on mimicking photosynthesis could enable cleaner energy production. So while most people take photosynthesis for granted, it’s worth appreciating as the miraculous foundation of Earth’s interdependent web of life.
Key Takeaways
- Photosynthesis converts sunlight into energy, producing oxygen gas as a byproduct
- The oxygen released by photosynthesis makes up about 21% of Earth’s atmosphere
- Nearly all aerobic life, including humans, relies on photosynthetic oxygen to survive
- Green plants and phytoplankton produce the vast majority of the planet’s oxygen
Resources
Graça, A. T. (2024). Light’EM up!: structural characterization of light-driven membrane protein complexes by cryogenic electron microscopy. Diva Portal. https://www.diva-portal.org/smash/record.jsf?pid=diva2:1832794
Souici, B. (2023). The landscape urban planning approach for improving urban air quality, case study of Algiers, Algeria. Mediterranean Cities Journal. https://mediterranean-cities.com/index.php/JMC/article/download/22/29
