Question

Give comparison between the following: C3 and C4 pathways

Answer 1

Part 1:Location

• C3 pathway is also known as Calvin cycle. This cycle occurs in mesophyll cells present in the leaves of C3 plants.
• C4 pathway is also known as Hatch and Slack pathway
• This cycle occurs in mesophyll cells and bundle sheath present in the leaves of C4 plants.
• Unlike C3 plants, the Calvin cycle in C4 plants occurs in the bundle sheath cells.

Part 2 :Pathway-C3 & C4

Part 3:First stable product formed

• In C3 pathway the first stable product of this pathway is 3-Phosphoglycerate.
• In C4 pathway the first stable product is OAA (oxaloacetic acid).

Part 4:Primary $C{O}_2$ acceptor C3 pathway vs C4 pathway $\begin{array}{ccc}\text{Criteria}& \text{C3 pathway}& \text{C4 pathway}\\ \text{Mesophyll cells}& \text{Occurs in the mesophyll cells.}& \text{Occurs in mesophyll and bundle sheath cells.}\\ \text{First stable product}& \text{First stable product formed is PGA. PGA is a 3 carbon compound, thus the pathway is called C3 cycle.}& \text{First stable product formed is OAA. OAA is a 4 carbon compound, thus the pathway is called C4 cycle.}\\ \text{Primary}C{O}_2\text{acceptor}& \text{Primary}C{O}_2\text{acceptor is RuBP.}& \text{Primary}C{O}_2\text{acceptor is PEP.}\end{array}$