C3, C4, and CAM Plants + Preknowledge

Electron Transfer Phosphorylation

• Final step of aerobic respiration (what we see in the ETC)

• Eukaryotes — occurs in the inner membrane of mitochondria

• Prokaryotes — occurs at infoldings of the inner plasma membrane

• Produces 30-32 ATP

Photorespiration

• process in plants

  • enzyme RuBisCO accidentally binds to oxygen instead of carbon dioxide and a loss of fixed carbon

    • undoing some of the work done by photosynthesis

• occurs primarily under conditions of high light and low carbon dioxide levels (like hot, dry weather, and is considered a wasteful process that reduces photosynthetic efficiency)

C3 Plants

• Type of plant that uses only the Calvin-Benson cycle to fix carbon

• The majority of plants; which have no special features to combat photorespiration

• Thrive in moderate climates with moderate sunlight and water

  • Ex: Trees, shrubs, wheat, rice

• (CO₂ is being used in the calvin cycle)

C4 Plants

• Plants that fix carbon twice, in two kinds of cells

• common in habitats that are hot, and they include crabgrass, sugarcane and corn

  • reactions begin in mesophyll cells where carbon is fixed by an enzyme that doesn’t need oxygen, malate (an intermediate) is moved into bundle-sheath cells where its converted back to CO₂

  • Rubisco fixes carbon for the second time when the CO₂ enters the Calvin cycle

CAM Plants

• Type of plant that conserves water by fixing carbon twice, at different times of day

• Plants that are adapted to dry environments, such as cacti and pineapples

  • Stomata open at night, when temperatures are lower, to minimize evaporative water loss

  • Malate (an intermediate) is stored in the cell’s central vacuole

    • When stomata close the next day, the malate is moved out of the vacuole and converted back to CO₂

• Rubisco fixes carbon for the second time as CO₂ enter the Calvin-Benson cycle