Question

How do relative concentration of the oxygen and co2 affect the activity of the rubisco?

Answer 1

RUBISCO is an enzyme which can function both as corboxylase and oxygenase .That means it can bring carboxylation when CO2 +RUBP combine. It can also bring RUBP+O2 reaction.
Which reaction occurs depends on the concentration of O2 and CO2 in the atmosphere and also temperature.
When temerature is high and O2 concentrations are mroe RUBISCO functions as oxygenase and brings photorespiration in plants which is a loss to plant.
When O2 is less and CO2 is at its normal levels, RUBISCO brings carboxylation and normal photosynthesis occurs.