Question

why is carboxylation influenced by the CO2/O2 ratio?

Answer 1

Carboxylation is a chemical reaction in which a carboxylic acid group is produced by treating a substrate with carbon dioxide. An example of  carboxylation is that coupling atmospheric carbon dioxide to a sugar which is catalysed by the enzyme RuBisCO. (Ribulose-1,5-bisphosphate carboxylase/oxygenase).

Rubisco has a higher affinity for oxygen when temperature increased and at mild temperatures, rubisco's affinity for carbon dioxide is about 80 times higher than its affinity for oxygen. So hot, dry conditions tend to cause more photorespiration and normal temperature tend to follow the calvin cycle that is process of carbon fixation, rubisco incorporates carbon dioxide into an organic molecule during the first stage of the Calvin cycle.

By comparing between photorespiration and the normal Calvin cycle, showing how many fixed carbons are gained or lost when either 6 carbon dioxide or 6 oxygen molecules are captured by rubisco. Photorespiration results in a loss of 3 fixed carbon atoms under these conditions, while the Calvin cycle results in a gain of 6 fixed carbon atoms.

By the above phenomenon it is said that carboxylation influenced by the CO2/O2 ratio