Photorespiration takes place in which of the following organelles? A) Chloroplast and mitochondria B) Mitochondria and peroxisome C) Bundle sheath cells and Chloroplasts D) Chloroplast peroxisome and mitochondria
Hint: Photorespiration is a process that involves the loss of fixed carbon as $CO_2$ in plants in the presence of light. It is initiated in chloroplasts. This process does not produce ATP or NADPH and is a wasteful process.
Photorespiration occurs usually when there is a high concentration of oxygen. Under such circumstances, RuBisCO, the enzyme that catalyzes the carboxylation of RuBP during the first step of the Calvin cycle, functions as an oxygenase. Some amount $O_2$ does bind to the RuBisCO and hence $CO_2$ fixation is decreased.
Now consider the options given above:
A) Chloroplast and Mitochondria are involved in the process of photorespiration and these two alone cannot help to start the process of photorespiration, hence, the option is incorrect.
B) Mitochondria and peroxisome are involved in the process of photorespiration and these two alone cannot help to start the process of photorespiration, hence, the option is incorrect.
C) Bundle sheath cells and Chloroplasts, among these only chloroplasts, help in the initiation of the process of photorespiration, and bundle sheath cells do not play any role in the process and cannot be considered in this process, hence this option is also considered void.
D) Chloroplast peroxisome and mitochondria, in this the RuBP binds with $O_2$ to form one molecule of PGA and phosphoglycolate in the pathway of photorespiration. Photorespiration involves three organelles, chloroplast, peroxisomes, and mitochondria.
Note: In $C_4$ plants, photorespiration does not occur. This is because these plants have a mechanism that increases the concentration of $CO_2$ at the enzyme site.