AP BIOLOGY

Detailed explanation-1: -Photorespiration begins in the chloroplast, when rubisco attaches O 2 O 2 O2start text, O, end text, start subscript, 2, end subscript to RuBP in its oxygenase reaction. Two molecules are produced: a three-carbon compound, 3-PGA, and a two-carbon compound, phosphoglycolate.

Detailed explanation-2: -An enzyme, RuBisCO, catalyzes the fixation reaction, by combining CO2 with RuBP. The resulting six-carbon compound is broken down into two three-carbon compounds, and the energy in ATP and NADPH is used to convert these molecules into G3P.

Detailed explanation-3: -During the C4 pathway, when the C4 acid from the mesophyll cells is broken down in the bundle sheath cells, it releases CO2-this results in increasing the intracellular concentration of CO2. So, RuBisCO functions as a carboxylase and binds with plants and carry out more carboxylation.

Detailed explanation-4: -Carboxylation is catalyzed by ribulose bisphosphate carboxylase/oxygenase (Rubisco), which can constitute up to 50% of the soluble protein in a leaf and is probably the Earth’s most abundant protein. The combination of CO2 with RuBP, a five-carbon compound, yields two molecules of the three-carbon compound 3-PGA.