Science

How does photosynthesis work?

Most people know that plants — especially the green ones — are important because they take in carbon dioxide and turn it into oxygen. Even major urban areas have made it a priority to go green by planting more trees to improve air quality. But have you ever wondered how plants turn a waste product into something positive? It’s all thanks to a process called photosynthesis. And if it’s been a while since you were in a biology course, get ready for a refresher.

What is photosynthesis?

Close up photo on green plant cells
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In its simplest form, photosynthesis is the process of creating sugar to support growth and development. Plants rely on water, sunlight (or artificial light), and carbon dioxide as the raw materials that are turned into sugar (glucose). In an interesting twist, oxygen is produced as a waste byproduct of photosynthesis — which explains why green spaces are so critical in urban areas. It’s a similar concept to how the human body breaks down food into nutrients to help it grow and thrive.

Do all plants perform photosynthesis?

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Plants aren’t the only living beings that rely on photosynthesis. Algae, some bacteria, and even protozoa (single-celled organisms) use the process to create energy. For the purpose of this article, we’re going to focus on plants. But keep in mind that the process would be similar for bacteria or protozoa.

Okay, so how does photosynthesis work?

Close up photo of green plant cells
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Photosynthesis happens at the cellular level. But to understand the process, we need to take a few steps back. As we mentioned before, for plants to create energy, they need a few raw materials: water, carbon dioxide, and a light source. We’ll focus on sunlight, but the process is the same with artificial light. The water is drawn through a plant’s roots. Carbon dioxide is absorbed through the plant’s surface — usually the leaves and stems. Likewise, sunlight is also absorbed through the plant’s surface.

So photosynthesis happens everywhere?

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Yes and no. Photosynthesis takes place within a plant’s cells, but only in one specific location — the chloroplast. A chloroplast is like the mitochondria of animals but for a plant cell. They help to produce energy, power the cells and are found only in organisms that conduct photosynthesis. The chloroplast is full of chlorophyll, a green pigment that absorbs sunlight. And this is how the chemical reaction begins.

A chemical reaction?

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There is a chemical equation that explains photosynthesis: 6H2O + 6CO2+ Light Energy → C6H12O6+ 6O2. Translated into words, this means that the chlorophyll within a chloroplast takes in six molecules each of water and carbon dioxide. With the help of sunlight, those 12 molecules are transformed into one glucose molecule and six oxygen molecules.

The glucose is essential for cell function and energy, while the oxygen molecules are considered waste and are released back into the environment through the plant’s pores or stoma. This chemical reaction takes place in all of the chloroplasts in a plant’s cells and occurs continuously throughout the day. Some of the glucose is used right away to provide energy for the plant, and some is stored for use during the night when photosynthesis doesn’t occur.

Putting it all together

Aerial photo of a river surrounded by bright green treese
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Plants often get ignored as a pretty backdrop or decor prop, but they’re critical to our environment and ecosystem. Plants are more than just a food source. Thanks to photosynthesis, they help to filter carbon dioxide and supply our world with a steady supply of fresh air. This is why green spaces matter and environmentalists sound the alarm over concerns like deforestation. So, the next time you’re strolling through the park or going camping in the woods, you can give a silent (or not so silent) thank you to all those plants for keeping your air clean.