5.4 - Alternative Mechanisms of Carbon Fixation

Rubisco

An enzyme that catalyzes CO2 fixation.

Photorespiration

Process where Rubisco binds O2 instead of CO2.

Stomata

Pores on leaves controlling gas exchange.

Waxy Cuticle

Waterproof layer preventing water loss in plants.

C3 Plants

Plants using standard Calvin Cycle for carbon fixation.

C4 Plants

Plants with an additional carbon fixation pathway.

CAM Plants

Plants fixing CO2 at night to reduce water loss.

Bundle-Sheath Cells

Cells surrounding veins in C4 plants, reducing O2 exposure.

Mesophyll Cells

Cells where initial CO2 fixation occurs in C4 plants.

PEP Carboxylase

Enzyme with higher affinity for CO2 than O2.

Oxaloacetate

Intermediate produced in C4 carbon fixation pathway.

Malate

Product of oxaloacetate reduction in C4 pathway.

Pyruvate

End product of malate oxidation in bundle-sheath cells.

ATP Hydrolysis

Process providing energy for C4 cycle regeneration.

Calvin Cycle

Main pathway for carbon fixation in plants.

Nitrogen Demand

Amount of nitrogen required for plant growth.

Malic Acid

Stored form of CO2 in CAM plants.

Guard Cells

Cells regulating the opening and closing of stomata.

Cyclic Light Reactions

Light-dependent reactions producing ATP in photosynthesis.

Desert Adaptation

Survival strategies of plants in arid environments.

Energy Efficiency

Balance of energy use versus carbon fixation.

Water Loss

Evaporation of water affecting plant survival.

High CO2 Concentration

Favors Rubisco's carboxylase activity in Calvin Cycle.

O2 Concentration

21% in atmosphere, affecting photorespiration rates.