Question

PEP case has an advantage compared to rubisco. The advantage is that

• A. rubisco fixes carbon dioxide only in $C_4$ plants, but PE.P case does it in both $C_3$ and $C_4$ plants
• B. PEPcase is present in both mesophyll and bundle sheath cells, but rubisco is not
• C. rubisco is subject to photorespiration, but PEPcase is not
• D. PEP case conserves energy but rubisco does not

Answer 1

The correct option is C rubisco is subject to photorespiration, but PEPcase is not

PEPCase is the acronym for the enzyme phosphoenolpyruvate carboxylase. Like RUBISCO, PEPCase "fixes" carbon dioxide into an organic molecule. Unlike, RUBISCO, PEPCase does not react with oxygen (no photo-respiration). It also has a higher affinity for CO₂ than RUBISCO does. Some plants are able to combat the limitations of Rubisco and the C3 pathway. They have this PEP carboxylase, a carbon-fixing enzyme in addition to Rubisco. This catalyzes the conversion of 3 carbon phosphoenolpyruvate (PEP) to oxaloacetate.

So, the correct option is, 'rubisco is subject to photorespiration, but PEPcase is not'.