Answer:
RuBisCO has a much greater affinity for CO2 than
for O2. It is the relative concentration of O2 and CO2
that determines which of the two will bind to the enzyme.
In
plants
some O2 does bind to RuBisCO and hence, CO2 fixation is-
decreased. Here the RuBP instead of being converted to two molecules of PGA
binds with O2 to form one molecule and phosphoglycolate in a pathway
called photorespiration. In the photorespiratory pathway, there is neither
synthesis of sugars, nor of ATP. Rather it results in the release of' CO2
with the utilization of ATP. In the photorespiratory pathway. There is no
synthesis of ATP or NADPH. Therefore, photorespiration is a wasteful process.
In
plants,
photorespiration does not occur. This is because they have a mechanism that
increases the concentration of CO2 at the enzyme site. This takes
place when the C4 acid from the mesophyll is broken down in the bundle cells to
release this
results in increasing the intracellular concentration of.
In turn, this ensures that the RuBisCO functions as a carboxylase minimizing
the oxygenase activity.
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