photorespiration
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Article
19 sectionsContents
- Photorespiratory reactions
- Substrate specificity of RuBisCO
- Conditions which affect photorespiration
- Altered substrate availability: lowered {{CO2}} or increased O<sub>2</sub>
- Increased temperature
- Biological adaptation to minimize photorespiration
- Biochemical carbon concentrating mechanisms
- C<sub>4</sub>
- CAM (Crassulacean acid metabolism)
- C<sub>2</sub>
- Algae
- Biophysical carbon-concentrating mechanisms
- Eukaryotic algae
- Hornworts
- Cyanobacteria
- Possible purpose of photorespiration
- See also
- References
- Further reading
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Photorespiration (also known as the oxidative photosynthetic carbon cycle or C2 cycle) refers to a process in plant metabolism where the enzyme RuBisCO oxygenates ribulose 1,5-bisphosphate (RuBP), wasting some of the energy produced by photosynthesis. The desired reaction is the addition of carbon dioxide to RuBP (carboxylation), a key step in the Calvin–Benson cycle, but approximately 25% of reactions by RuBisCO instead add oxygen to RuBP (oxygenation), creating a product that cannot be used within the Calvin–Benson cycle. This process lowers the efficiency of photosynthesis, potentially lowering photosynthetic output by 25% in plants. Photorespiration involves a complex network of enzyme reactions that exchange metabolites between chloroplasts, leaf peroxisomes and mitochondria.