Question

The Rubisco enzyme is regulated by numerous conditions. Do you expect Rubisco activity to increase or decrease for each of the following conditions? Explain your answer.

a. When the amount of carbon dioxide in the stroma increases.

b. When the amount of Mg²⁺in the stroma decreases.

c. When the amount of H⁺ in the stroma decreases.

d. When the amount of reduced ferredoxin in the stroma increases

Answer 1

a. When the amount of carbon dioxide in the stroma incresase; Increased concentration of CO₂ in stroma increases the activity of RUBISCO.

b. When the amount of Mg2⁺ decreases in the stroma; Mg2⁺ is the cofactor for RUBISCO enzyme. This more important for the proper activity of RUBISCO. If Mg2⁺ level decreases in the stroma then RUBISCO activity decreases.

c. When the amount of H+ in the stroma decreases; When the amount of H⁺ decreases, then the pH of stroma increases. This leads to the activation of RUBISCO enzyme activity. The optimum pH for the RUBISCO is around 9.

d. When the amount of reduced ferredoxin in the stroma increases; Increase in amount of reduced ferredoxin at stroma increase the activity of RUBISCO. Reduced ferredoxin, reduces the thioredoxin. This reduced thio redoxin reduce the disulfide bind of RUBISCO thereby, activates the enzyme.