There are two types of photoreceptors:

Rods 

Cones

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#Unit 6. System Physiology – Plant

Rubisco-activase is regulated by light via the ferredoxin–thioredoxin system.

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#Unit 6. System Physiology – Plant

Ribulose 1,5-bisphosphate are sugar phosphates (SugP) inhibits carbamoylation by binding tightly to the active site and locking the enzyme in the “closed” confirmation.

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#Unit 6. System Physiology – Plant

Rubisco is inhibited by the natural inhibitor 2‐carboxyarabinitol 1‐phosphate (CA1P), that is a structural analog of the six-carbon intermediate of the carboxylation reaction. 

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#Unit 6. System Physiology – Plant

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#Unit 6. System Physiology – Plant

CA1P and the other bound sugar phosphates are specifically removed by the ATP‐dependent enzyme, Rubisco activase, which prepares Rubisco for the catalytic cycle.

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#Unit 6. System Physiology – Plant

When dark‐treated chloroplasts are exposed to light;

The flow of protons from the stroma into the thylakoid lumen is coupled to the release of Mg2+ from the intrathylakoid space to the stroma.