TLS Online TPP Program

#Id: 7273

#Unit 6. System Physiology – Plant

Upon illumination, the flow of protons from the stroma into the thylakoid lumen is coupled to the release of Mg2+ from the intra thylakoid space to the stroma. These light actuated ion fluxes decrease the stromal concentration of protons (the pH increases from 7 to 8) and increase that of Mg2+ by 2 to 5 mM. 

TLS Online TPP Program

#Id: 7274

#Unit 6. System Physiology – Plant

The light-mediated increase of pH and the concentration of Mg2+ activate enzymes of the Calvin–Benson cycle that require Mg2+ for catalysis and are more active at pH 8 than at pH 7: rubisco, fructose 1,6-bisphosphatase, sedoheptulose 1,7-bisphosphatase, and phosphoribulokinase.  The modifications of ionic composition of the chloroplast stroma are reversed rapidly upon darkening.

TLS Online TPP Program

#Id: 7275

#Unit 6. System Physiology – Plant

Light regulates the catalytic activity of four enzymes of the Calvin–Benson cycle directly via the ferredoxin– thioredoxin system

TLS Online TPP Program

#Id: 7276

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7277

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7278

#Unit 6. System Physiology – Plant

Two chloroplast proteins ferredoxin–thioredoxin reductase and thioredoxin regulate five pivotal enzymes within minutes of the

light–dark transition: