Question

in photo respiration rubisco 6 fix oxygen into two carbon compound and three carbon compound namely phospho glycolic acid and phospho glyceric acid.where does the phospho glyceric goes.where it is used or regenerated ???

Answer 1

In the presence of excess oxygen and low C02 , ribulose 1) 1,5 diphosphate produced in the chloroplast during photosynthesis is split into 2 phospho glycolic acid and 3 phospho glyceric acid by the enzyme, ribulose 1,5 diphosphate oxygenase 2) The 3 phospho glyceric acid enters the Calvin cycle. 3) In the next step, phosphate group is removed from 2 phosphoglycolic acid to produce glycolic acid by the enzyme, phosphatase. 4) Glycolic acid then it come out of chloroplast and enter the peroxisome. Here, it combines with oxygen to form glyoxylic acid and hydrogen peroxide. This reaction is catalyzed by the enzyme, glycolic acid oxidase. Hydrogen peroxide is toxic and it is broken down into water and oxygen by the enzyme, Catalase. Photorespiration is an oxidation process. In this process, glycolic acid is converted into carbohydrate and C02 is released as the by product. As glycolic acid is oxidized in photorespiration, it is also called as glycolate metabolism. 5) The glyoxylic acid converted into glycine by the addition of one amino group with the help of the enzyme, amino transferase. 6) Now, the glycine is transported from the peroxisome into the mitochondria. In the mitochondria, two molecules of glycine condense to form serine and liberate carbon dioxide and ammonia. 7) Amino group is removed from serine to form hydroxyl pyruvic acid in the presence of the enzyme, transaminase. 8) Hydroxy pyruvic acid undergoes reduction with the help of NADH to form glyceric acid in the presence of enzyme alpha hydroxyl acid reductase. 9) Finally, regeneration of 3 phosphoglyceric acid occurs by the phosphorylation of glyceric acid with ATP.