Why Photosynthesis is Important

By: Laurie L. Dove  | 
Clover, like all plants with chlorophyll, creates energy through photosynthesis.
Michael Moller/EyeEm/Getty Images

It's a concept most children learn in science class: Photosynthesis can convert solar energy to chemical energy. It's the energy production and fuelling process that allows plants and even algae to survive and grow. But, before we get in to why photosynthesis is important, it's time to break down the particulars of this essential biological process.

What is Photosynthesis?


Photosynthesis is a vital process through which green plants, algae, and certain bacteria convert light energy, typically from the sun, into chemical energy in the form of glucose or sugar. This process occurs in specialized structures called chloroplasts, located within the cells of these living organisms [source: National Geographic].

To understand photosynthesis, let's break down the word itself. "Photo-" comes from the Greek word for light, and "-synthesis" means putting together. In essence, photosynthesis is "putting together with light."

Here's a basic breakdown of the process:

  1. Absorption of light: The chlorophyll, a green pigment present in the chloroplasts, absorbs light energy.
  2. Conversion and storage of energy: This absorbed light energy is then used to convert carbon dioxide (CO2) from the atmosphere and water (H2O) from the soil into glucose (C6H12O6). Oxygen (O2) is released as a by-product.
  3. Usage and storage: The produced glucose is either used by the plant for energy, stored as starch, or used to build other organic compounds like cellulose.

While it may seem like a simple exchange, photosynthesis is a complex series of reactions that can be split into two main stages:

  1. Light dependent reactions: A light dependent reaction takes place in the thylakoid membranes of the chloroplasts and produce ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate) by utilizing light energy. Oxygen is released in this stage.
  2. Light independent reactions (Calvin Cycle): These reactions occur in the stroma of the chloroplasts. The ATP and NADPH produced in the previous stage are used here to convert CO2 into glucose.

Photosynthesis is the foundation of life on Earth. Not only does it provide food for plants themselves, but it also sustains the animals and humans that feed on those plants.

Moreover, photosynthesis releases oxygen, which is essential for the respiration of most life forms. As a bridge between the sun's energy and life on Earth, photosynthesis ensures the continuation of life as we know it.


Photosynthesis and Carbon Dioxide: A Crucial Relationship

Most modern environmental conversations centre around carbon dioxide, fossil fuels, and conservation. As such, the unique relationship between photosythesis and carbon dioxide deserves a closer look.

Carbon dioxide (CO2) does indeed play a pivotal role in the process of photosynthesis, serving as one of the primary raw materials. To produce energy, plants effectively consume carbon dioxide and water, release oxygen. As one could imagine, this process has far-reaching implications for our planet's climate, atmosphere, and ecosystems.


  1. Role of Carbon Dioxide in Photosynthesis: During photosynthesis, plants take in CO2 from the atmosphere. This CO2, combined with the energy from sunlight captured by chlorophyll, is used to convert water (taken up by the plant's roots) into glucose. This glucose is then used by the plant as an energy source or stored for later use.
  2. The Carbon Cycle and Equilibrium: Photosynthesis and respiration form a balanced cycle on Earth. While photosynthesis consumes CO2 to produce glucose and release oxygen, respiration by animals and plants does the opposite. They use oxygen to break down glucose for energy, releasing CO2 in the process. Ideally, this cycle would keep the amount of atmospheric CO2 and oxygen in balance.
  3. Photosynthesis as a Carbon Sink: Forests, algae, and other photosynthetic organisms act as carbon sinks, removing significant amounts of CO2 from the atmosphere. This helps mitigate the greenhouse effect to a certain extent, as increased levels of atmospheric CO2 can lead to global warming. By absorbing CO2, photosynthetic organisms play a crucial role in regulating global carbon levels and thus, climate.
  4. Human Activity and Photosynthesis: Deforestation and other human activities have disrupted the carbon balance. Removing large numbers of trees means fewer carbohydrate molecules are absorbed by the atmosphere, leading to increased greenhouse gas levels. This, coupled with the burning of fossil fuels, which releases ancient carbon stores into the atmosphere, has resulted in a significant spike in atmospheric CO2 levels, accelerating the greenhouse effect.
  5. Enhancing Photosynthetic Efficiency: Researchers are exploring ways to boost the efficiency of photosynthesis, especially in staple crops. By doing so, crops could potentially remove more CO2 from the atmosphere while also providing increased yields. Some strategies include altering the way plants absorb light or modifying the process to make it more responsive to current CO2 levels.

Photosynthesis regulates atmospheric composition, supports the food chain, and counteracts some of the impacts of human-induced climate change. Recognizing and respecting this relationship is vital for the future health of our planet [source: NASA].


What if Photosynthesis Stopped Working?

If photosynthesis came to an abrupt end, most plants would die within short order. Although they could hold out for a few days -- or in some cases, a few weeks -- how long they lived would largely be a factor of how much stored energy their cells contain.

Large trees, for example, could soldier on for several years — perhaps even a few decades — because of their energy stores and the slow rate of use. However, the majority of plants would meet a withering end, and so would the animals that rely on them to produce oxygen.


With all the herbivores dead, the omnivores and carnivores would soon follow. Although these meat-eaters could feed on all the carcasses strewn about, that supply wouldn't last more than a few days. Then the animals that temporarily relied on them for sustenance would die.

That's because, for photosynthesis to cease to exist, Earth would have to plunge into darkness. To do this, the sun would have to disappear and plunge Earth's surface temperatures into a never-ending winter of bitter cold temperatures. Within a year, it would bottom out at minus 100 degrees Fahrenheit (minus 73 degrees Celsius), resulting in a planet of purely frozen tundra [source: Otterbein].

Ironically, if the sun burned too bright, it could cause photosynthesis to stop occurring. Too much light energy would damage plants' biological structure and prevent photosynthesis from happening. This is why the photosynthetic process, in general, shuts down during the hottest hours of the day.

Whether the culprit were too much sunlight or not enough, if photosynthesis stopped, plants would stop converting carbon dioxide -- an air pollutant -- to organic material. Right now, we rely on photosynthetic plants, algae and even bacteria to recycle our air. Without them, there would be less oxygen production.

Even if all the plants on Earth were to die, people would remain resourceful -- especially if their lives depended on it. An artificial photosynthesis process being developed by scientists could just become the world's biggest problem-solver. Using an artificial "leaf," scientists have successfully harnessed sunlight and recreated photosynthesis.

The leaf is actually a silicon solar cell that, when put in water and exposed to light, then generates oxygen bubbles from one side and hydrogen bubbles from the other -- essentially splitting oxygen and hydrogen. Although the idea was designed as a way to potentially produce clean electrical energy, there are implications for recreating a photosynthetic atmosphere as well [source: Chandler].


Lots More Information

Related Articles

  • Chandler, David. "'Artificial Leaf' Makes Fuel From Sunlight." MIT. Sept. 30, 2011. (April 12, 2015) http://newsoffice.mit.edu/2011/artificial-leaf-0930
  • Hubbard, Bethany. "The Power of Photosynthesis." Northwestern University. Nov. 19, 2012. (April 12, 2015) https://helix.northwestern.edu/article/power-photosynthesis
  • Otterbein, Holly. "If the Sun Went Out, How Long Could Life on Earth Survive?" Popular Science. July 16, 2013. (April 12, 2015) http://www.popsci.com/science/article/2013-07/if-sun-went-out-how-long-could-life-earth-survive