3.4 - CAM and C4 plants

C4 Plants Examples: Maize, sugarcane, sorghum. Adaptation: Found in hot, dry environments to minimize photorespiration. Key Enzyme: PEP carboxylase, which has a high affinity for CO₂ and does not react with O₂, reducing photorespiration. Pathway: CO₂ + PEP (3C) → Oxaloacetate (4C) → Malate (4C). Malate is transported to bundle-sheath cells, where CO₂ is released for the Calvin cycle. CAM (Crassulacean Acid Metabolism) Plants Examples: Pineapple, cacti, succulents. Adaptation: Found in arid environments; adapted to conserve water. Stomata Behavior: Stomata open at night to minimize water loss. Key Enzyme: PEP carboxylase, similar to C4 plants, used for initial carbon fixation at night. Pathway: CO₂ + PEP → Oxaloacetate (4C) → Malate (4C), which is stored in vacuoles as malic acid overnight. During the day, malic acid is broken down to release CO₂ for the Calvin cycle.