Final answer:
In photorespiration, two molecules of glycine are converted into one molecule of serine and one molecule of CO2 through an enzymatic reaction in the peroxisomes and mitochondria, not during the Calvin cycle that occurs in the chloroplasts.
Step-by-step explanation:
In photorespiration, two molecules of glycine are combined in a reaction to produce one molecule of serine and one molecule of CO2. This process takes place in the peroxisomes and mitochondria of plant cells. The enzyme responsible for this reaction is part of a metabolic pathway that helps to metabolize the toxic byproduct phosphoglycolate, which is produced during photorespiration. The Calvin cycle, in contrast, is where the enzyme RuBisCO fixes carbon dioxide into an organic molecule, 3-PGA. The Calvin cycle occurs in the chloroplasts and does not produce toxic byproducts. This cycle is part of photosynthesis, which, alongside cellular respiration, forms a crucial energy cycle necessary for the life processes of plants. Both of these cycles highlight the dual roles of chloroplasts and mitochondria in plant cells.