Photosynthesis and the Light Independent Reaction

Question 1

What is the Light Independent Reaction?

Answer 1

• Aka the Calvin Cycle.
• Occurs in the stroma of chloroplasts.
• Uses NADPH2 and ATP made during light dependent reactions to produce glucose.
• Cyclical reactions are similar to the Krebs Cycle.

Question 2

What are the 3 Phases of the Light Independent Reaction?

Answer 2

1. Carbon Fixation
2. Reduction Reactions
3. Regeneration of RuBP (Ribulose 1,5 bisphosphate)

Question 3

What is Phase 1 of the Calvin Cycle?

Answer 3

It is the Carbon Fixation.
- 3CO2 are added to RuBP to form 3 unstable 6-carbon intermediates.
- The intermediates split into six 3-carbon molecules called PGA.
- These reactions are catalyzes by rubisco.

Question 4

What is Phase 2 of the Calvin Cycle?

Answer 4

It is known as the Reduction Reactions.
- 6 PGAs are phosphorylated by 6 ATPs to form 6 molecules of 1, 3 -BPG.
- 6 NADPH molecules reduce the six 1,3-BPG to 6 G3P or PGAL.
- One molecule of G3P exits the cycle as a final product.

Question 5

What is Phase 3 of the Calvin Cycle?

Answer 5

Known as the Regeneration of RuBP.
- 3 ATP are used to rearrange the remaining 5 G3P into 3 molecules of RuBP.
- The cycle continues with RuBP fixing more CO2.

Question 6

What is the reaction needed to Produce One G3P?

Answer 6

3 RuBP + 3 CO2 + 9 ATP + 6 NADPH + 5 H2O –> 9 ADP + 8P + 6 NADP+ +G3P + 3RuBP