Phase 2: The Calvin Cycle

• a.k.a The Dark

Reactions

Products of Phase 1 are used in Phase 2

• ATP Energy• NADPH e-

(electrons)

Stage 2: Calvin Cycle

• Purpose: • Make sugar by reducing carbon dioxide (adding e-)

• Location:• Stroma of chloroplast

Stage 2: Calvin Cycle

• Requires: ATP*• Electrons (NADPH)*

• CO2

• Enzymes

Stage 2: Calvin Cycle

• Produces • Glucose

A brief note about Rubisco

• Enzyme that attaches CO2 to 5-carbon compound in Calvin cycle

• Most abundant protein on the earth!• Rate limiting – a slow enzyme (~ 3 /

sec.)• Genetic engineers trying to make a

more efficient Rubisco

• Calvin cycle

Calvin Cycle

1. CO2 enters cycle by becoming attached to a 5-Carbon RuBP

2. produces 6-carbon molecule (unstable)

3. Breaks into two 3-carbon molecules

Calvin Cycle

4.Energy is used (ATP ADP)

5.Electrons used (NADPH NADP+)

6. 3-Carbon compound leaves Calvin cycle

Calvin Cycle

7. Two 3-Carbon groups combine to become glucose

8. Remaining 3-Carbon groups continue through cycle to regenerate starting 5-Carbon RuBP

9. Six CO2 to produce 1 glucose(6 turns of the cycle required)

Important molecules are recycled

• ATP ADP

• NADPH NADP+

• 5-Carbon RuBP recycles

Photosynthesis Summary

Input:LightWaterCO2

Photosynthesis Summary

Output:

O2

Glucose

Photosynthesis Summary

Recycle:ATPElectron

carriers5-Carbon

RuBP

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