How Does Photorespiration Counter Photosynthesis?

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.