Plant lecture 4 - Rubisco

Question 1

4 Factors required for net CO2 assimilation Calvin cycle

Answer 1

1. Irreversible. Keq for Ru1,5BP → 3PG = 10^6
   - Means ↑ photosynthesis products even when ↓ precursor
2. 1st step has ↑ affinity for CO2. Km = 9um (E close to saturation in physiological conditions)
3. Regenerates initial CO2 acceptor
4. Cycle adjusts levels of RuBP to ensure con. of CO2 acceptor = maximum

Question 2

Rubisco effector activation

Answer 2

• Activator = carbamylated
• Inhibitor = decarbamylated form
• Inhibitor to decarbamylated shifts eq. to decarbamylated form so ↑ proportion of E = inactive
• Tight-binding inhibitors, released slowly
• E.G = RuBP itself. Binds to inactive decarbam. form + released v slowly