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Have you ever took a breath? When you breathe, do you ever wonder where the oxygen comes from? Me neither. Though, imagine a world without greenery, without any oxygen- now, visualize the process which powers all life as we know: Photosynthesis.
What is photosynthesis?
Photosynthesis is a series of chemical reactions which converts carbon dioxide, water, and sunlight to oxygen and glucose. It takes place in plants, and can take anywhere from a few seconds to hours to happen.
Outside the plant
You may be unfamiliar with glucose. Glucose is a sugar which plants use as food. Unlike us humans, plants can't get up and get a snack or cook something. To solve this issue, they use photosynthesis. First, carbon dioxide, sunlight, and water enter the plant. Carbon dioxide will be turned into glucose for the plant to use, sunlight will be used as energy (ATP), and water will be turned into oxygen. That is the outside of photosynthesis, however, have you ever wondered what happens on the inside? As much as I’d like to say ‘me neither,’ I have. And that’s exactly what this article will answer. First, let us focus on what is needed to initiate photosynthesis.
Sunlight enters
The first thing that enters the plant is sunlight. It enters a part of the plant called the thylakoid, whose purpose during photosynthesis is to convert water into oxygen. The thylakoid has pigments inside of them, which is specifically where the sunlight hits. When the sunlight hits the first pigment, the energy will be absorbed into the plant cells. Inside the plant cells are electrons, which the energy goes to. A molecule called NADP+ then helps the energy be carried to the electrons. Once the energy is all absorbed, the electrons will be ‘excited'. They'll be excited because everyone has absorbed enough energy, and now electrons can exit which will lead to the next step of photosynthesis. When they exit however, who will replace them? That question is the reason oxygen gets released; and it is through a chemical reaction.
Oxygen is released
This reaction causes the water molecules to separate from the oxygen. You see, in a water molecule, there is oxygen too. By splitting the water and oxygen, air is released. Oxygen is actually a waste product. You may ask why, if the plant did not need oxygen, why did it create it? That ties to our previous question as for who will replace the exiting electrons. The splitting of water will create the electrons needed to replace the existing ones while releasing oxygen. The electrons which were released by water splitting remain until next time the plant initiates photosynthesis. Then, they will get excited and exit, be replaced, and the cycle continues.
This is a water molecule. As you may notice, there is oxygen. When the plant splits the oxygen, then an electron is created.
Glucose is formed
The next step in photosynthesis begins when the excited electrons go to the enzymes. The enzyme's role in photosynthesis is to generate the necessary items to create glucose, or food for the plant.
At the beginning, the sunlight hit a pigment, which eventually led to oxygen being created. This time, sunlight will hit a second pigment, not leading to more oxygen, but to its target: glucose. To form glucose for the plant, you need ATP and NADPH. ADP is a molecule which transfers and provides cells with energy. Even though ADP does have a very important role in science, its main purpose in photosynthesis is to be converted into ATP. This is because ATP is mainly what cells use to power work, allowing cells to perform chemical reactions needed to produce oxygen and glucose.
It also converts NADP+ to NADPH. I mentioned NADP+ earlier, its purpose being to help the chlorophyll molecule absorb energy. It will be created into NADPH, as NADPH is needed to perform the chemical reactions to create glucose. The ATP and NADPH serve as a source of power for the process of carbon dioxide turning into glucose (also known as the Calvin cycle). Once the chemical reaction will process, the plant will have glucose.
*A visual on the calvin cycle.
Looking back
Photosynthesis is a process which powers life on earth, which starts out with Sunlight, carbon dioxide, and water, and ends with not only food or the plant but the precious oxygen we breathe. I hope you enjoyed reading this article just as much I enjoyed writing it :)
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