Metabolic Processes L9 - Alternative Mechanisms to Carbon Fixation

What are problems with calvin cycle to fix carbon

When O2 binds with RuBisCO instead of CO2.

How have cells developed alternative pathways to fix carbon

Plants have developed alternative pathways to fix carbon so there is a high concentration of CO2 in the plant cell. This pathway builds CO2 concentration to enter the Calvin cycle.

Draw C4 cycle and calvin cycle in C4 plants

• More oxygen gets into mesophyll cell because it is closer to surface of the leaf (through stomata)

Which cell does the C4 pathway occur

In C4 photosynthesis plants, the C4 pathway occurs in the mesophyll cell, and the calvin cycle occurs in the bundle sheath cell.

• An enzyme (not RuBisCO) helps bring CO2 into the cell for carbon fixation (in bundle sheath cell)

List order of molecule names in the C4 cycle

CO₂ + PEP 🡪 oxaloacetate (reduced by NADPH) 🡪 malate 🡪 CO₂ + pyruvate

How do C4 plants complete C4 pathway and Calvin cycle

Simultaneously but in different areas

How do CAM plants complete C4 pathway and Calvin cycle

In the same area but during different times.

At night: Stomata opens to release O2 and allow CO2 in: C4 cycle occurs and CO2 is fixed into malate

At day: Stomata closes to prevent water loss: malate is oxidized into pyruvate and CO2 is released into the Calvin cycle.