The concentration of CO2 in the earth\'s atmosphere has increased from 1960 to 2

Question

The concentration of CO2 in the earth's atmosphere has increased from 1960 to 2016 (Figure 1). What is the effect of increased CO2 on photorespiration? For this question, do not consider components of global climate change other than increased atmospheric CO2. (1 point) a) Increased CO2 has no effect on rates ofphotorespiration because the oxygenation reaction ofRUBISCO is completely independent from the carboxylation reaction of RUBISCO More CO2 in the atmosphere decreases rates of photorespiration because RUBISCO is more likely to catalyze the reaction between phosphoglycolate and O2 instead of the reaction between 3-phosphoglyecrate and CO2. b) c) More CO2 in the atmosphere decreases rates of photorespiration because RUBISCO is more likely to catalyze the reaction between ribulose bisphosphate and CO2 instead of the reaction between ribulose bisphosphate and O2 More CO2 in the atmosphere increases rates of photorespiration because RUBISCO is more likely to perform the carboxylase reaction More CO2 in the atmosphere increases rates of photorespiration because RUBISCO is more likely to perform the oxygenase reaction d) e) 400 Actual concentration Seasonally corrected data a 380 E 360 340 320 1960 1970 980 1990 2000 2010 Year Figure 1. Atmospheric CO2 concentration at Mauna Loa observatory

Explanation / Answer

PHOTORESPIRATION:

O2 inhibits photosynthesis inC3 plants. this phenomenon originally is known as the Warburg effect, was later recognized as the light-dependent release of CO2  due to oxygenase activity of RuBisCO is a bifunctional enzyme. it catalyzes both the carboxylation and the oxygenation of RuBP. At low CO2 concentrations, RuBisCo performs the oxgenase activity. oxygenation of RuBP leads to the production of one molecule of 3-phosphoglycerate and 2- phosphoglycerate.

2-Phosohoglycolate produced by RuBisCo when it oxygenates RuBP cannot be utilized within in the calvin cycle. the pathway by which 2-Phosohoglycolate is further metabolized is described as glycolate pathway (C2 cycle or oxidative photosynthetic carbon cycle). The pathway involves three subcellular compartments, the chloroplasts, peroxisomes and mitochondria. The key features of the pathway are the conversion of two-carbon molecule: 2-phosphoglycolate to two molecules of glycine and decarboxylation of two molecules of glycine to serine, CO2 and NH3. The three-carbon molecule serine is then converted into 3-phosphoglycerate, which re-enters the Calvin cycle. The release of CO2 in this process decreases the photosynthetic output and limits the plant biomass production.

so, The rate of photorespiration was decreased little as the CO2 concentration was increased.

the correct answer is "b".

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