Cellular energetics is the foundation of life, exploring how cells manage energy to sustain biological functions. In AP Biology Unit 3, students learn about energy transformations, enzyme function, and metabolic pathways like photosynthesis and cellular respiration. Understanding these processes is crucial for mastering biological systems and their real-world applications
Comprehensive Study Guide for Unit 3
- 3.0 Overview: Cellular Energetics – 6 min read
- 3.1 Enzyme Structure – 3 min read
- 3.2 Enzyme Catalysis – 4 min read
- 3.3 Environmental Impacts on Enzyme Function – 2 min read
- 3.4 Cellular Energy – 4 min read
- 3.5 Photosynthesis – 3 min read
- 3.6 Cellular Respiration – 3 min read
- 3.7 Energy & Fitness – 2 min read
Key Concepts in Cellular Energetics
1. Energy & Metabolism
- Energy is the capacity to perform work, crucial for life processes.
- Metabolism encompasses all biochemical reactions within an organism.
- First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.
- Second Law of Thermodynamics: Every energy transfer increases entropy (disorder).
2. Enzymes & Their Role in Metabolism
- Enzymes are biological catalysts that speed up reactions by lowering activation energy.
- Active site: The specific region where a substrate binds to an enzyme.
- Factors Affecting Enzyme Activity:
- Temperature & pH: Extreme values can denature enzymes.
- Substrate Concentration: Higher concentrations increase reaction rates until saturation.
- Inhibitors:
- Competitive inhibitors bind to the active site.
- Non-competitive inhibitors alter enzyme shape by binding elsewhere.
3. ATP: The Energy Currency of the Cell
- Adenosine triphosphate (ATP) stores and releases energy for cellular functions.
- ATP is produced via:
- Substrate-level phosphorylation (direct transfer of phosphate groups).
- Oxidative phosphorylation (electron transport chain & chemiosmosis).
- Photophosphorylation (light-dependent reactions in photosynthesis).
4. Cellular Respiration: Energy Production
- Cellular respiration converts glucose into ATP via three main stages:
- Glycolysis (cytoplasm) – Breaks glucose into pyruvate; net gain: 2 ATP & 2 NADH.
- Citric Acid Cycle (Krebs Cycle) (mitochondria) – Completes glucose oxidation; produces 2 ATP, NADH, FADH2, CO2.
- Electron Transport Chain & Oxidative Phosphorylation (mitochondrial membrane) – Generates ~34 ATP using oxygen as the final electron acceptor.
- Anaerobic respiration (fermentation) occurs without oxygen, producing lactic acid (animals) or ethanol (yeast).
5. Photosynthesis: Capturing Light Energy
- Photosynthesis occurs in chloroplasts, converting sunlight into chemical energy.
- Two stages:
- Light-dependent reactions (thylakoids): Convert light energy into ATP & NADPH.
- Calvin Cycle (stroma): Uses ATP & NADPH to fix CO2 into glucose.
- Adaptations:
- C3 Plants: Use the Calvin Cycle normally (most plants).
- C4 & CAM Plants: Adapted for dry environments, minimize photorespiration.
AP Biology Exam Tips for Unit 3
- Understand key processes: Enzyme function, ATP production, and energy transformations.
- Memorize key equations:
- Cellular respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
- Photosynthesis: 6CO2 + 6H2O + light → C6H12O6 + 6O2
- Practice with diagrams: Be able to label mitochondria, chloroplasts, and enzyme structures.
- Use past AP questions: Solve FRQs related to energy transfer and metabolism.
Final Thoughts
Mastering cellular energetics is essential for AP Biology success. By understanding enzymes, ATP, cellular respiration, and photosynthesis, you’ll be well-prepared for the AP exam. Keep practicing with diagrams, equations, and real-world applications to reinforce your learning
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