BIO203H5 Lecture Notes - Lecture 8: C4 Carbon Fixation, Carbon Fixation, Light-Independent Reactions
Document Summary
Why do plants often struggle to achieve high concentrations of co2 to sustain photosynthesis: evolutionary aspects of rubisco. > avoidance of photoinactivation and damage of photosynthetic membranes. Keeps [co2] in leaves close to co2-compensation point, even when stomata are closed. Sustains turnover of photosynthetic apparatus when stomata are closed. A simple solution: more is always better - keep intracellular co2 concentration high! C4 photosynthesis initial carbon fixation in c4 plants differs from c3 plants. C4 plants: carbon fixation occurs independently of the calvin cycle. Carboxylation reaction is increasingly inefficient when temperature increases: Increase of the oxygenase activity (o2 to rib1,5bp) Decrease of the carboxylation activity (co2 to rib1,5bp) Separate place of carbon fixation and rubisco carboxylation. Use pep-carboxylase for carbon fixation (not affected by high o2, higher affinity for co2) Increase co2 concentrations directly where the calvin-cycle occurs within photosynthetic active cells. C4 pathway occurs mostly in plants from hot, dry habitats. Cam plants details of their exciting night life.
