Question

When CO2 levels are low and O2 levels are high, a process called photo respiration makes it so that photosynthesis is inefficient because RuBisCO will add….And why is it not A.

Answer 1

RuBP oxygenase-carboxylase (rubisco) is a key enzyme in photosynthesis. This enzyme can use carbon dioxide and oxygen as substrates.

→ During photosynthesis, in the first stage of the Calvin cycle, this enzyme incorporates carbon dioxide into the organic molecule ribulose 1,5 diphosphate forming a sugar molecule.

→During photorespiration, the enzyme attaches oxygen to its oxygenase reaction and produces two molecules, one three-carbon compound called 3-PGA, and another two-carbon compound called phosphoglycolate.

3-PGA can enter the Calvin cycle but phosphoglycolate cannot enter it, and thus two carbons are eliminated from it which leads to a decrease in sugar synthesis, making photosynthesis less efficient.

So, the statement in option A indicates the normal function of the rubisco during photosynthesis.

The correct option is B.