Rubisco is an important enzyme in the Calvin cycle because it acts as a carboxylase to catalyze ...

Answer:
a) Rather than the carboxylase activity yielding two molecules of 3-phosphoglycerate to feed into the Calvin cycle, rubisco oxygenase activity yields one three-carbon product (3-phosphoglycerate) and one two-carbon product (phosphoglycolate) that cannot be used directly in the next step of the Calvin cycle. Producing the two-carbon product appears to be a wasteful diversion of material from carbon assimilation.
b) The Earth's atmosphere contains a much higher concentration of O2 than CO2, so oxygenase activity could have a significant negative impact on carbon fixation.
c) The glycolate pathway transforms 75 percent of the phosphoglycolate carbon into 3-phosphoglycerate and the remaining 25 percent is released as CO2.
d) Higher temperatures decrease carbon dioxide solubility relative to oxygen solubility. In addition, these plants close their stomata to reduce water loss, which further reduces the CO2 concentration in the leaf.
e) C4 plants confine rubisco to cells containing high carbon dioxide levels. CAM plants only open their stomata at night.