Question

Inhibition of photosynthesis in high concentration of oxygen is mainly due to

• A. distribution of $RuBP$ carboxylase.
• B. inactivation of $RuBP$ carboxylase.
• C. non-synthesis of $RuBP$ carboxylase.
• D. $RuBP$ carboxylase acting as oxygenase.

Answer 1

Answer: (D)

C4 carbon fixation or the Hatch–Slack pathway is one of all three known photosynthetic methods of carbon fixation. C4 photosynthesis reduces photorespiration via concentrating CO₂ around RuBisCO. To ensure that RuBisCO works in an environment in which there is a lot of carbon dioxide and very little oxygen, C4 leaves normally differentiate two in part remoted booths known as mesophyll cells and package-sheath cells. CO₂ is to start with constant inside the mesophyll cells through the enzyme PEP carboxylase, which reacts to the 3-C phosphoenolpyruvate (PEP) with CO2 to shape the four carbon oxaloacetic acid (OAA). OAA can be chemically reduced to malate or transaminated to aspartate. Those diffuse to the package sheath cells, wherein they are decarboxylated, growing a CO₂ in a wealthy environment around RuBisCO and thereby suppressing photorespiration. The resulting pyruvate (PYR) collectively with about half of the phosphoglycerate (PGA) produced by RuBisCO diffuse returned to the mesophyll. PGA is then chemically decreased and diffuses back to the bundle sheath to complete the reductive pentose phosphate cycle (RPP). This alternate of metabolites is critical for C4 photosynthesis to carry out.