Biology / Unit 3 Bio 0606 short lesson, about 20 seconds
C4 Photosynthesis: Bundle Sheath Cells and PEP Carboxylase
Captions available
The idea
C4 plants fix carbon dioxide twice: first with PEP carboxylase in mesophyll cells, then again by RuBisCO in bundle sheath cells.
In practice
Corn's bundle sheath cells wrap each leaf vein, keeping local carbon dioxide high enough for RuBisCO to avoid oxygen.
Where people slip
PEP carboxylase does not replace RuBisCO — it concentrates carbon dioxide so RuBisCO fixes it without binding oxygen.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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