Boundless Biology by Lukas Waller

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.

Location: Takes place in the stroma of the chloroplast. Phases of the Calvin Cycle: Carbon Fixation: Reduction Phase: Regeneration of RuBP: Key Enzyme: RuBisCO is the primary enzyme, acting as both a carboxylase and an oxygenase. Can bind to CO₂ (carboxylation) or O₂ (oxygenation), the latter leading to photorespiration, which reduces efficiency. Energy Requirement: For each full turn of the cycle (producing 1 G3P): To produce one glucose molecule, the cycle must run twice, requiring: Products: G3P is the direct product, which can be used to form glucose and other carbohydrates. Photorespiration Issue: Occurs when RuBisCO fixes O₂ instead of CO₂, leading to wasteful energy loss. More likely in hot, dry climates when stomata close to conserve water. Adaptations: C4 and CAM plants have evolved mechanisms to minimize photorespiration and improve efficiency, which will be explored further.

Things To Remember Cyclic Photophosphorylation occurs as a means to produce additional ATP rather than ATP and NADPH. This is because the Calvin Cycle (next episode) requires more ATP than NADPH. PSI = Photosystem 1, PSII = Photosystem 2 Diagrams Noncyclic Photophosphorylation: ⁠https://cdn.kastatic.org/ka-perseus-images/faeb1179a538a3a8106fa5f3b9bd90c92f9834a7.png⁠ Cyclic Photophosphorylation: https://cdn.kastatic.org/ka-perseus-images/d47991f2cf9c7a4fc22f055b60793af8c341991f.png Quizzes https://quizlet.com/30876000/light-dependent-reactions-light-independent-reactions-flash-cards/

Key Terms, try drawing these out. A) Leaf Anatomy palisade layer cuticle layer spongy layer vascular bundle (xylem/phloem) stomata guard cells epidermis (upper/lower) B) Chloroplast Anatomy membrane (inner/IMS/outer) thylakoid membrane thylakoid lumen thylakoid lamella granum C) When do stomata open and how do they do so? Topics not covered in-depth: Sunlight triggers [K+] ion movement which requires ATP from the plant in order to open guard cells.