Chapter 8 General Biology Overview

Photoautotrophs Organisms that produce their own food using light energy (e.g., plants, algae, cyanobacteria). Q: What term describes organisms like plants that use light to make food? A: Photoautotrophs. Photosynthesis Process converting CO₂ + H₂O → glucose + O₂ using sunlight. Q: What is the chemical equation for photosynthesis? A: CO₂ + H₂O → glucose + O₂. Chloroplast Organelle in plant cells where photosynthesis occurs. Q: Where does photosynthesis occur in plant cells? A: Chloroplast. Thylakoid Membrane-bound discs in chloroplasts where light reactions occur. Q: Light reactions happen in the __________ of chloroplasts. A: Thylakoid. Stroma Fluid-filled space in chloroplasts where the Calvin cycle occurs. Q: The Calvin cycle takes place in the __________. A: Stroma. Stomata Leaf pores for gas exchange (CO₂ in, O₂ out). Q: Name the pores that allow CO₂ to enter leaves. A: Stomata. Chlorophyll Pigment absorbing blue/red light; reflects green. Q: Which pigment makes plants appear green? A: Chlorophyll. Carotenoids Accessory pigments absorbing blue/green light; protect chlorophyll. Q: Pigments like carotenoids absorb __________ light. A: Blue/green. Photosystem II (PS II) Protein-pigment complex that splits water and initiates the electron transport chain. Q: Which photosystem is involved in splitting water? A: PS II. Photosystem I (PS I) Protein-pigment complex that re-energizes electrons to make NADPH. Q: NADPH is produced in __________. A: PS I. Electron Transport Chain (ETC) Proteins in the thylakoid membrane that transfer electrons and pump H⁺ ions. Q: The ETC helps create a gradient of __________ ions. A: H⁺. ATP Synthase Enzyme that produces ATP as H⁺ ions flow through it. Q: ATP is synthesized by __________. A: ATP synthase. NADPH Electron carrier molecule used in the Calvin cycle. Q: What molecule carries electrons to the Calvin cycle? A: NADPH. Photolysis Splitting of water into O₂, H⁺, and electrons using light. Q: The splitting of water is called __________. A: Photolysis. Calvin Cycle Light-independent reactions that fix CO₂ into glucose. Q: The Calvin cycle is also called the __________ reactions. A: Light-independent. RuBisCO Enzyme that fixes CO₂ to RuBP in C₃ plants. Q: The most abundant enzyme on Earth is __________. A: RuBisCO. RuBP Ribulose bisphosphate; a 5-carbon molecule that binds CO₂. Q: CO₂ binds to __________ in the Calvin cycle. A: RuBP. 3PG (3-Phosphoglycerate) First stable molecule formed after CO₂ fixation. Q: The first product of CO₂ fixation is __________. A: 3PG. G3P (Glyceraldehyde-3-Phosphate) 3-carbon sugar used to make glucose, starch, and lipids. Q: G3P is a precursor to __________. A: Glucose. Photorespiration Wasteful process where O₂ binds RuBisCO instead of CO₂. Q: Photorespiration reduces efficiency in __________ plants. A: C₃. C₃ Plants Plants using only the Calvin cycle (e.g., rice, wheat). Q: Most plants are classified as __________ plants. A: C₃. C₄ Plants Plants that spatially separate CO₂ fixation (mesophyll) and the Calvin cycle (bundle sheath). Q: Corn uses the __________ pathway. A: C₄. CAM Plants Plants that fix CO₂ at night and run the Calvin cycle during the day (e.g., cacti). Q: CAM plants open stomata at __________. A: Night. PEP Carboxylase Enzyme in C₄/CAM plants with high CO₂ affinity. Q: PEP carboxylase minimizes __________. A: Photorespiration. Malate Molecule that stores CO₂ in C₄/CAM plants. Q: In CAM plants, CO₂ is stored as __________. A: Malate. Bundle Sheath Cells Cells in C₄ plants where the Calvin cycle occurs. Q: The Calvin cycle occurs in __________ cells in C₄ plants. A: Bundle sheath. Mesophyll Cells Leaf cells where CO₂ fixation occurs in C₃/C₄ plants. Q: In C₄ plants, CO₂ is fixed in __________ cells. A: Mesophyll. Glucose Phosphate Molecule derived from G3P; precursor to sucrose and starch. Q: Glucose phosphate is used to make __________. A: Starch/sucrose. Sucrose Disaccharide used for energy transport in plants. Q: Plants transport sugar as __________. A: Sucrose. Starch Polysaccharide used for long-term energy storage. Q: Starch is stored in plant __________. A: Roots/leaves. Cellulose Polysaccharide in plant cell walls. Q: Plant cell walls are made of __________. A: Cellulose. ATP Energy currency molecule produced in light reactions. Q: ATP is synthesized during the __________ reactions. A: Light. NADP+ Electron carrier molecule reduced to NADPH. Q: NADP+ becomes __________ after accepting electrons. A: NADPH. Electromagnetic Spectrum Range of light wavelengths; plants use visible light (400-700 nm). Q: Chlorophyll absorbs __________ light. A: Visible. Visible Light Wavelengths (400-700 nm) used in photosynthesis. Q: Plants primarily use __________ light for photosynthesis. A: Visible. Redox Reaction Reaction involving electron transfer (CO₂ is reduced, H₂O is oxidized). Q: In photosynthesis, CO₂ is __________. A: Reduced. Light Reactions Phase converting sunlight to ATP and NADPH. Q: ATP and NADPH are produced in the __________. A: Light reactions. Cyclic Electron Flow Pathway producing ATP only (no NADPH or O₂). Q: Cyclic flow uses only __________. A: PS I. Noncyclic Electron Flow Pathway producing ATP, NADPH, and O₂. Q: Noncyclic flow involves both __________. A: PS II and PS I. Photophosphorylation ATP synthesis using light energy. Q: ATP production via light is called __________. A: Photophosphorylation. Light-Dependent Reactions Phase converting sunlight into ATP and NADPH; occurs in thylakoids. Key Steps: PS II Activation: Chlorophyll absorbs light, energizing electrons. Water Splitting (Photolysis): Releases O₂, H⁺, and electrons. ETC & ATP Synthesis: Electrons move through ETC, pumping H⁺ to generate ATP via ATP synthase. PS I Activation: Re-energized electrons reduce NADP⁺ to NADPH. Pathways: Noncyclic: Uses PS II and PS I → ATP + NADPH + O₂. Cyclic: Uses PS I only → ATP (no NADPH/O₂). Calvin Cycle (C₃ Pathway) Light-independent reactions in stroma; converts CO₂ → glucose. Phases: Fixation: CO₂ + RuBP → 3PG (catalyzed by RuBisCO). Reduction: 3PG → G3P (uses ATP/NADPH). Regeneration: G3P regenerates RuBP; surplus forms glucose. Photorespiration Adaptations C₃ Plants: Fix CO₂ directly in mesophyll (e.g., rice, wheat). C₄ Plants: Spatially separate CO₂ fixation (mesophyll → malate) and Calvin cycle (bundle sheath). CAM Plants: Temporally separate CO₂ fixation (night) and Calvin cycle (day). Products of Photosynthesis Immediate: G3P → glucose, sucrose (transport), starch (storage), cellulose (cell walls). Secondary: Lipids, amino acids, nucleotides. 2. Study Guide Structure Section 1: Introduction to Photosynthesis Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂; ecological role as the foundation of food chains. Section 2: Structures & Pigments Chloroplast: Thylakoids (light reactions) + stroma (Calvin cycle). Pigments: Chlorophyll (absorbs blue/red), carotenoids (absorbs blue/green). Section 3: Light Reactions Detailed steps (PS II → ETC → PS I → ATP/NADPH). Cyclic vs. noncyclic pathways. Section 4: Calvin Cycle Phases (fixation, reduction, regeneration). Role of RuBisCO and G3P utilization. Section 5: Photorespiration & Adaptations Comparison Table: Feature C₃ Plants C₄ Plants CAM Plants CO₂ Fixation Direct in mesophyll Mesophyll → malate Night (stored as malate) Calvin Cycle Same cells (mesophyll) Bundle sheath cells Day (using stored malate) Examples Rice, wheat Corn, sugarcane Cacti, pineapple