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.

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