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Photosynthesis: What Really Makes the World Go Round
- PBMG
- 2 days ago
- 3 min read
Illustration and Photo by Emmy Ulmschneider
By Emmy Ulmschneider, Master Gardener
Before I retired, I taught science to fourth graders in Midland’s GT program. As a scientist myself, I wanted my students to love science as I knew it: asking and answering questions about big ideas. And one of those big ideas was looking at how our world functions: Where does the energy come from that keeps most living things on earth alive? How is that energy converted to a form we can use? The answer is that for most of us, the sun is our primary source of energy, and that energy is harnessed primarily by plants through the process called photosynthesis. What?!?!?!?
One way that all organisms are connected is through the energy that they need to stay alive. That energy comes to us in the form of the chemical bonds of the food we eat. Our Earth runs, primarily, on the sun’s energy. Plants (producers) capture the sun’s energy through the process of photosynthesis. What sets plants and other one celled, photosynthetic organisms apart as producers is their ability to take carbon dioxide (CO2) and water (H2O), turn it into sugar, (CH2O) and in the process release oxygen (O2). Think of a plant as a food and oxygen factory. So, how do the plants do this? That is the miracle of photosynthesis and the chloroplast! Gases like CO2 and water vapor (H2O) enter a leaf through small openings called stomata. These gases diffuse through the plant until they enter a small structure called a chloroplast, which is filled with the green pigment chlorophyll. Within the chloroplast, in the presence of chlorophyll, light energy from the sun is transformed into the chemical energy of sugar. When exposed to light, chlorophyll in the chloroplast is used to break apart the CO2 (carbon dioxide) and H2O (water)molecules and then recombine the atoms to make CH2O (glucose sugar). The food that the plant makes, in the form of sugar, is used to provide energy for the plant. The extra sugar that the plant does not use is stored as starch for later use. To see this visually, try
And in turn, this stored energy can be transferred up the food chain to any consumer that eats the plant or a lower-level consumer. A plant harnesses about 1% of the sun's energy that falls on its leaves. Each member of a food chain (or trophic level), in turn, uses about 10% of the available energy in the bodies of the organisms that they eat. The other 90% of the energy is lost into the atmosphere. Eventually, when an organism dies, its body is broken down into component parts by decomposers. These component parts are then available to plants, and the cycle starts over again.
These building materials of life are recycled repeatedly and have been for eons. And it all starts with the sun, a plant, a chloroplast, carbon dioxide, and water! So, the next time you take a deep breath, have a salad for lunch, or a burger for dinner, thank a photosynthetic plant.
If you have questions, call the AgriLife office in Odessa at 498-4071 or in Midland at 686-4700. Additional information, and our blog for access to past articles, is available at westtexasgardening.org. Click on “Resources.”
Photo by Emmy Ulmschneider