what is photorespiration and organelles involved in photorespiration are............?
Photorespiration is the light dependent process of oxygenation of ribulose phopshate and release of carbon dioxide by the photosynthetic organs of a plant. The organelles involved in photorespiration are chloroplast, peroxisome and mitochondrion. Photorespiration is a cyclic process. It occurs at high temperature in C3 plants. At high temperature RuBP carboxylase functions as oxygenase instead of carboxylase and instead of fixing carbon dioxide, oxidises ribulose 1,5-biphosphate to a 3-carbon phosphoglyceric acid and a 2-carbon phosphoglycolate. Phosphoglyceric acid produced is used up in Calvin cycle. Phosphoglycolate is hydrolysed to form glycolate. Glycolate passes into peroxisome of the mesophyll cell where it is oxidised to glyoxylate. Glyoxylate is aminated and gives rise to amino acid glycine. Glycine enters mitochondrion where two molecules of glycine condense to form a molecule of serine. Carbon dioxide and ammonia are released in the process. Serine is taken up by the peroxisome and deaminated to form glycerate. The latter passes into chloroplasts for synthesis of photosynthetic products as wells as photorespiration. In photorespiration two molecules of phosphoglycolate formed by oxygenation of RuBP is changed into 1 molecule of phosphoglycerate and one molecule of carbon dioxide.