Question

Diffentiate between c3 and c4 cycle.

Answer 1

Calvin Cycle or C3 Cycle 

The Calvin cycle was observed by Melvin Calvin in Chlorella, an unicellular alga. Hence it is called so. In this reaction carbon dioxide is converted into sugars. So it is a process of carbon fixation.



The first stable compound produced in Calvin cycle is a 3 carbon compound namely 3 phosphoglyceric acid (PGA). Hence Calvin cycle is also called C3 cycle. 

Hatch and Slack Cycle

C4 is the alternative pathway of Calvin cycle (C3 cycle) taking place during the dark phase of photosynthesis.



In the C4 cycle the first stable compound is 4 carbon compound, namely oxaloacetic acid. Hence it is called C4 cycle. It is a process of carbon dioxide fixation. This pathway was worked out by Hatch and Slack (1966). Hence the C4 cycle is also called Hatch- Slack cycle.