Biology Essentials Lecture 13: Free Energy Capture and Storage

Overview

• Focuses on photosynthesis and respiration
• Photosynthesis map shows its occurrence on land and ocean
• Highest in areas like Amazon, Eastern North America, Northern Europe, and Asia

Free Energy and Life

• ATP Production: Goal of life is to create ATP
• Autotrophs: Make their own food (e.g., plants)
  • Use photosynthesis (light reaction and Calvin cycle)
• Heterotrophs: Consume other organisms for food (e.g., humans)
  • Use cellular respiration

Photosynthesis

• Process
  • Converts carbon dioxide and water into glucose and oxygen
  • Energy stored in glucose bonds (positive Delta G)
• Components
  • Light Reaction
    • Occurs in thylakoid membrane of chloroplasts
    • Uses water and light to produce ATP, NADPH, and releases oxygen
  • Calvin Cycle
    • Takes place in the stroma of chloroplasts
    • Uses ATP, NADPH, and carbon dioxide to produce sugars
• Evolution
  • Early life forms used photosynthesis
  • Oxygen production started ~2 billion years ago

Chemosynthesis

• Used by organisms without light availability
• Example: Tube worms in deep oceans use chemosynthesis
  • Utilize hydrogen sulfide gas to produce carbohydrates

Cellular Respiration

• Process
  • Breaks down glucose with oxygen to produce carbon dioxide, water, and ATP
  • Exergonic reaction (releases energy)
• Stages
  • Glycolysis: Occurs outside mitochondria, produces pyruvate
  • Krebs Cycle: Takes place in the mitochondrial matrix, stores energy in NADH and FADH2
  • Electron Transport Chain: Occurs along the inner mitochondrial membrane
    • Electrons from NADH and FADH2 create a proton gradient to synthesize ATP
  • Oxygen acts as final electron acceptor, forming water

Alternative Processes

• Fermentation: Used when oxygen is not available
  • Examples include alcoholic fermentation and lactic acid fermentation

Key Takeaways

• Photosynthesis and respiration represent the cycles of energy capture and release
• Photosynthesis stores energy in glucose bonds while respiration releases it for ATP production
• Both processes are crucial for maintaining energy flow in ecosystems