Question

Which of the following statements regarding photorespiration are true?

• A. Photorespiration is a metabolically expensive pathway
• B. Photorespiration is avoided when CO${}_2$ is abundant
• C. Photorespiration results in loss of usable carbon dioxide
• D. All of the above

Answer 1

The correct option is D All of the above

Photorespiration occurs in 3 different organelles namely mitochondria, peroxisome and chloroplast. In photorespiration or C${}_2$ cycle there is no formation of ATP or any energy providing compound. It picks O${}_2$ as a substrate instead of CO${}_2$ during photorespiration.
In the photorespiratory pathway, there is neither synthesis of sugars, nor of ATP. If carbon dioxide is abundantly available, RUBISCO acts as a carboxylase rather than an oxygenase.
Photorespiration uses as much ATP as photosynthesis but results in no energy gains for the plant and has carbon dioxide as a lost by-product. Hence, all options are correct.