How Does Photorespiration Counter Photosynthesis?

Photosynthesis and photorespiration are two reactions that occur in plant life. Both of them are designed to turn light and gas into energy, however photorespiration actually results in a loss of energy for the plant.

Photosynthesis

Photosynthesis is the process of converting solar energy into chemical energy. During photosynthesis, plants utilize light to break down carbon dioxide. In photosynthesis, two 3-phosphoglycerates (PGA) are created, which the plant can use to create sugar.

Photorespiration

Photorespiration happens when there isn't much carbon dioxide in the air for the plant to utilize. The plant uses oxygen instead of carbon dioxide to produce energy. Photorespiration produces 1 PGA and 1 Phosphogylcolate.

Photosynthesis vs. Photorespiration

Photorespiration produces 1 PGA, so it may appear beneficial at first glance, however you also have to consider what happens to the phosphogylcolate, which plants don't have much use for. Plants convert the phosphoglycolate into something useful, but at the expense of up to 40 percent of the energy stored in their sugars. Since photorespiration doesn't produce enough sugar to make up this cost, the process wastes the energy that was created through photosynthesis.

References

• uic.edu: Photosynthesis and Photorespiration
• Illinois.edu: The Photosynthetic Process
• McDaniel.edu: Photorespiration