AP Biology Unit 3: Cellular Energetics

Introduction

• Instructor: Glenn Wokenfeld (Mr. W), retired AP Biology teacher
• Focus: Enzymes, Cellular Energy, Photosynthesis, Cellular Respiration
• Resources: Checklist available at APbios.c/checklist, LearnBiology.com curriculum, Biom Mania AP Bio app

Topics Covered

1. Enzymes (Topics 3.1 to 3.3)
2. Cellular Energy (Topic 3.4)
3. Photosynthesis
4. Cellular Respiration

Enzymes

Key Properties

• Function: Catalyze reactions, lowering activation energy
• Specificity: Active site complements substrate's shape and charge
• Structure: Proteins with secondary, tertiary, quaternary structures
• Optimum Conditions: pH, temperature, ionic concentration

Factors Affecting Enzyme Activity

• pH Changes: Optimal pH for peak efficiency, deviations cause denaturation
• Temperature Changes: Increased activity up to a point, then denaturation
• Substrate Concentration: Initial increase in activity up to saturation
• Inhibition
  • Competitive: Foreign molecule blocks active site
  • Non-competitive: Foreign molecule binds to allosteric site

Cellular Energy

• Metabolic Pathway: Series of enzyme-catalyzed reactions
• Autotrophs vs. Heterotrophs
  • Photoautotrophs: Use sunlight (e.g., plants)
  • Chemoautotrophs: Use inorganic substances
  • Heterotrophs: Consume organic compounds
• Exergonic vs. Endergonic Reactions
  • Exergonic: Release energy (e.g., cellular respiration)
  • Endergonic: Require energy (e.g., photosynthesis)

ATP: Structure and Function

• Structure: Ribose sugar, adenine, three phosphates
• Function: Power cellular work, energy storage/release
• Energy Coupling: Exergonic reactions drive endergonic reactions

Photosynthesis

Overview

• Equation: 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
• Endergonic Process: Converts low-energy inputs to high-energy glucose
• Evolution: Evolved 3.5 billion years ago, created oxygen-rich atmosphere

Phases of Photosynthesis

1. Light Reactions
   • Location: Thylakoid membranes
   • Products: ATP, NADPH
   • Chlorophyll's Role: Absorbs light, boosts electron energy
2. Calvin Cycle
   • Phases: Carbon fixation, energy investment/harvest, regeneration
   • Inputs/Outputs: Uses CO2, produces sugars

Key Concepts

• Chlorophyll and Pigments: Absorb light at specific wavelengths
• Z Scheme: Describes electron flow in light reactions
• Chloroplast Structure: Adapted to facilitate photosynthesis

Cellular Respiration

Overview

• Equation: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP
• Exergonic Process: Releases energy, increases disorder
• Phases: Glycolysis, Link Reaction, Krebs Cycle, Electron Transport Chain

Detailed Phases

1. Glycolysis
   • Location: Cytoplasm
   • Phases: Investment, cleavage, energy harvest
   • Outputs: 2 ATP, 2 NADH, 2 pyruvate
2. Link Reaction
   • Process: Converts pyruvate to Acetyl-CoA
3. Krebs Cycle
   • Outputs per Cycle: 1 ATP, 3 NADH, 1 FADH2
4. Electron Transport Chain
   • Location: Mitochondrial inner membrane
   • Process: Electron flow powers ATP synthesis

Special Topics

• Anaerobic Respiration and Fermentation
  • Occurs: Lack of oxygen
  • Outputs: 2 ATP
  • Types: Alcohol (yeast), Lactic acid (muscles)
• Comparison to Photosynthesis: Similar mechanisms in ATP production

Conclusion

• Resources: LearnBiology.com for interactive tutorials, quizzes, and exam reviews
• Encouragement: Understanding these complex topics is crucial for success on exams