Question

what are C3 and C4 cycle

Answer 1

C3 (Calvin) cycle 
1. C3 cycle operates in all plants.

2. The primary CO2 acceptor is Ribulose bi phosphate (RUBP a 5 Carbon compound).

3. The first stable product is a 3-Carbon compound, phosphoglyceric acid (PGA).

4. The carboxylase enzyme is Rubisco.

5. Single CO2 fixation.

6. CO2 fixation is slow and less efficient.

7. Fixation of 1 molecule of CO2 requires 3 ATP and 2 NADH.

8. Only granal type of chloroplasts are involved.

9. Kranz anatomy is absent.

10. Cannot operate under very low CO2 concentration.

11. Oxygen has inhibitory effect of photosynthesis.

12. Sunlight reaches saturation point.

13. Occurs in plants like Mango, apple etc (C3 plants)

C4 (Hatch and Slack) cycle 
1. C4 cycle operates only in C4 plants.

2. The primary CO2 acceptor is Phosphoenol pyruvic acid (PEP, a 3 Carbon compound).

3. The first stable product is a 4-Carbon compound, oxalo acetic acid (OAA).

4. The carboxylase enzyme is PEP carboxylase and Rubisco.

5. Two CO2 fixation.

6. CO2 fixation is fast and more efficient.

7. Fixation of 1 molecule of CO2 requires 5 ATP and 3 NADH.

8. Granal and agranal (bundle sheath chloroplast) type of chloroplasts are involved.

9. The leaves have Kranz anatomy.

10. Can operate under very low CO2 concentration.

11. Oxygen has no inhibitory effect of photosynthesis.

12. Sunlight does not become saturates.

13. Occurs in plants like maize, sorghum etc(C4 plants)