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Overview of Cellular Energetics in AP Biology

Apr 22, 2025

AP Biology Unit 3: Cellular Energetics Lecture Notes

Introduction

  • Presenter: Glenn Wokenfeld (Mr. W), retired AP biology teacher.
  • Topics Covered:
    • Enzymes
    • Cellular energy and ATP
    • Photosynthesis (light reactions and Calvin cycle)
    • Cellular respiration (glycolysis, link reaction, Krebs cycle, electron transport chain)
  • Resources: LearnBiology.com, AP Bio curriculum, BioMania AP Bio app.

Enzymes (Topics 3.1 to 3.3)

Key Properties

  • Mostly proteins that catalyze reactions by lowering activation energy.
  • Highly specific due to active site's shape and charge complementarity to the substrate.
  • Have optimal conditions (pH, temperature, ion concentration).
  • Denaturation: A change in shape reducing enzyme function due to environmental changes.

Effects of Environmental Changes

  • pH: Enzyme activity peaks at optimum pH; decreases above/below due to denaturation.
  • Temperature: Increases enzyme activity up to an optimum point; decreases past it due to denaturation.
  • Substrate Concentration: Increases reaction rate until saturation point.

Inhibition

  • Competitive: Foreign molecules block active site.
  • Non-competitive: Foreign molecules bind to allosteric site altering active site shape.

Cellular Energy (Topic 3.4)

Metabolic Pathways

  • Series of enzyme-catalyzed reactions, e.g., glycolysis, Krebs cycle, Calvin cycle.
    • Linear (e.g., glycolysis) or cyclical (e.g., Krebs cycle, Calvin cycle).

Autotrophs vs. Heterotrophs

  • Autotrophs: Produce own food; include photoautotrophs (plants, cyanobacteria) and chemoautotrophs.
  • Heterotrophs: Obtain energy from organic compounds produced by other organisms.

ATP

  • Structure: Ribose sugar, adenine base, three phosphate groups.
  • Function: Energy currency of the cell.
  • Energy Coupling: Links exergonic and endergonic reactions, driving biological processes.

Photosynthesis

Overview

  • Process: Converts light energy into chemical energy in the form of glucose.
  • Equation: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂ (Endergonic)
  • Phases: Light reactions and Calvin cycle.

Light Reactions

  • Location: Thylakoid membranes.
  • Products: ATP, NADPH.
  • Inputs: Light, water.

Calvin Cycle

  • Phases: Carbon fixation, energy investment & harvest, regeneration of RuBP.
  • Outputs: Sugars; occurs in the stroma.

Cellular Respiration

Overview

  • Process: Converts glucose into ATP.
  • Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (Exergonic)
  • Phases: Glycolysis, link reaction, Krebs cycle, electron transport chain.

Glycolysis

  • Location: Cytoplasm.
  • Phases: Investment, cleavage, energy harvest.
  • Net Yield: 2 ATP, 2 NADH, 2 pyruvate.

Link Reaction

  • Process: Converts pyruvate to acetyl-CoA.

Krebs Cycle

  • Location: Mitochondrial matrix.
  • Outputs per Acetyl-CoA: 1 ATP, 3 NADH, 1 FADH₂, CO₂.

Electron Transport Chain

  • Location: Inner mitochondrial membrane.
  • Process: Oxidizes NADH/FADH₂, pumps protons to create gradient, produces ATP.

Fermentation

Anaerobic Respiration

  • Occurs: In absence of oxygen.
  • Process: Glycolysis plus fermentation to regenerate NAD⁺.

Types of Fermentation

  • Alcohol Fermentation: Produces ethanol and CO₂ (yeast).
  • Lactic Acid Fermentation: Produces lactic acid (muscle cells).

Conclusion

  • Emphasis on interactive learning and resources available at LearnBiology.com.
  • Encouragement to utilize tools and prepare thoroughly for exams.

These notes provide a comprehensive overview of AP Bio Unit 3 on Cellular Energetics, highlighting key concepts related to enzymes, metabolic pathways, photosynthesis, and cellular respiration. For more detailed study resources, visit LearnBiology.com.

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