Calvin Cycle and Hatch-Slack Cycle | Photosynthesis

The upcoming discussion will update you about the difference between Calvin Cycle and Hatch-Slack Cycle.

Difference # Calvin Cycle (C₃ Cycle):

1. Calvin Cycle operates in all plants.

2. Calvin Cycle has a slower rate of CO₂ fixation.

3. CO₂ once fixed is not released back.

4. The primary acceptor of CO₂ is RuBP, a 5-carbon compound.

5. The first stable product is 3-PGA, 3-carbon compound.

6. It cannot operate under very low CO₂ con­centration.

7. Fixation of one molecule of CO₂ requires 3 ATP and 2 NADPH₂ molecules.

8. Optimum temperature for the operation of C₃ cycle is 10-25°C.

9. There is a net gain of one hexose sugar of 6 CO₂ molecules fixed and reduced.

Difference # Hatch-Slack Cycle (C₄ Cycle):

1. Hatch-Slack Cycle operates in C₄ plants only.

2. Hatch-Slack Cycle has a faster rate of CO₂ fixation.

3. Fixed CO₂ is released back in bundle sheath cells where it is finally fixed and reduced by Calvin cycle.

4. The primary acceptor of CO₂ is PEP, a 3-carbon compound.

5. The first stable product is OAA, a 4-carbon compound.

6. Hatch-Slack Cycle can operate under very low CO₂ concen­tration.

7. Fixation of one molecule of CO₂ requires 2 ATP molecules in addition to that required in C₃ cycle.

8. Optimum temperature for the operation of C₄ cycle is 30 to 45°C.

9. Hatch-Slack Cycle has no such gain.