Modern theory / Theory of chemical Evolution

-Explain by Oparin and Haldane

-Experimentation by urey and miller

TLS Online TPP Program

#Id: 7270

#Unit 6. System Physiology – Plant

The binding of sugar phosphates, such as ribulose-1,5-bisphosphate, to rubisco prevents carbamylation. The sugar phosphates can be removed by the enzyme rubisco activase, in a reaction that requires ATP. The primary role of rubisco activase is to accelerate the release of bound sugar phosphates, thus preparing rubisco for carbamylation

TLS Online TPP Program

#Id: 7271

#Unit 6. System Physiology – Plant

Rubisco is also regulated by a natural sugar phosphate, carboxyarabinitol-1-phosphate, that closely resembles the six-carbon transition intermediate of the carboxylation reaction. This inhibitor is present at low concentrations in leaves of many species and at high concentrations in leaves of legumes such as soybean and bean. 

Carboxyarabinitol- 1-phosphate binds to rubisco at night, and it is removed by the action of rubisco activase in the morning, when photon flux density increases.

TLS Online TPP Program

#Id: 7272

#Unit 6. System Physiology – Plant

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