3.5.2.2 LIR photosynthesis (Calvin cycle)

Question 1

What is the purpose of the LIR and where does it occur?

Answer 1

• Process which fixes carbon dioxide into organic molecules

- occurs in the stroma of the chloroplasts

Question 2

What does the LIR require?

Answer 2

• Uses energy (from ATP)

- Uses electrons and H+ ions (from NADPH)

Question 3

What are the 3 stages

Answer 3

1. carbon fixation
2. reduction
3. regeneration

Question 4

Carbon fixation

Answer 4

• RuBP (5 carbon molecule) combined with CO2 (1 carbon molecule)
• catalysed by the enzyme RUBISCO

Question 5

What affects RUBISCO - why and how?

Answer 5

• rubisco is a free floating enzyme
• affected by temperature
• increased temperature = increased kinetic energy
• so increased number of enzyme substrate complexes

Question 6

Reduction

Answer 6

• GP (3 carbon molecule) reduced into TP (3 carbon molecule)
• requires energy from hydrolysis of ATP (into ADP + Pi)
• requires H+ from NADPH

Question 7

Regeneration

Answer 7

• 5 of every 6 carbons from TP molecules are used to regenerate RuBP
• This required hydrolysis of ATP
• 1 of every 6 carbons is removed from the cycle and used to produce organic molecules
• 6 turns of the Calvin cycle are needed to produce 2 molecules of TP and 1 molecule of glucose