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Synonyms for photorespiration
Photosynthetic carbon oxidation cycle
Mutant can be considerably less fit for survival with decelerated growth.
How can mutants grow normally like wildtypes?
Suppression of photorespiration by increasing CO2 levels from .035% to .1-.3% (increase by almost 100 fold)
3 organelles involved in photorespiration
Peroxisome (w/ catalase crystal), mitochondrion, and chloroplast.
Interaction between chloroplast and peroxisome where GLYCERATE is sent to chloroplast and 2 GLYCOLATE is sent to peroxisome.
- Glycerate used for R15BP synthesis.
- Glycolate used for a-ketoglutarate.
Glycolate is converted to __________ in peroxisome
2-phosphoglycolate -[phosphoglycolate phosphatase]-> glycolate + P
Glycolate + O2 -[glycolate oxidase]-> Glyoxylate + H2O2
*H2O2 -[catalase]-> (1/2)O2 + H2O
Glyoxylate -[A or B]-> Glycine
- A = Glutamate-glyoxylate aminotransferase; a-ketoglutarate
- B = Serine-glyoxylate aminotransferase; hydroxypyruvate
Peroxisome-Mitochondrium amino acid translocator
Serine (from mitochondrium) sent to peroxisome as 2 glycine (from peroxisome) sent to mitochondrium.
2 glycine used to generate NADH, CO2, NH4, and serine.
2 glycine are _______ in the mitochondria to yield _____
2 Glycine -[Glycine decarboxylase-serine hydroxymethyl transferase complex]-> Serine
CO2, NH4, NADH formed
Glycine decarboxylase-serine hydroxymethyl transferase
Ammonia released from mitochondrion is ________
assimilated in the chloroplast
Serine Peroxisome-chloroplast interaction
Serine -[Serine glyoxylate aminotransferase]-> Hydroxypyruvate
Hydroxypyruvate -[hydroxypyruvate reductase; NADH]-> D-glycerate
D-glycerate -[Glycerate kinase; ATP]-> 3-Phosphoglycerate
How does peroxisome get NADH for reduction of hydroxypyruvate to glycerate
Malate produced by chloroplast and mitochondrium is sent to the cytosol by the malate-oxaloacetate shuttle where it is turned to oxaloacetate and produces NADH
Possible biological functions of photorespiration
- 1. Help salvage carbon lost during rubisco oxygenase reaction
- 2. Protective function when dissipation of photosynthetic energy (ATP and reductant) is required.