6: Understanding Enzymes in Metabolism

Oct 9, 2024

Lecture Notes: Enzymes and Metabolism

Overview

  • Introduction to Chapter 6: Energy and Metabolism
    • Focus on biological aspects, skipping some chemistry parts
    • Importance of enzymes in biological reactions

Enzymes

  • Definition: Enzymes are proteins that act as biological catalysts to speed up chemical reactions
    • Most enzymes are proteins, but some RNAs have catalytic activity (ribozymes)

Enzyme Structure and Function

  • Active Site: Specific site where substrates bind

    • Substrate: Molecules that undergo the reaction
    • Formation of enzyme-substrate complex
    • Enzymes are not consumed in reactions
  • Mechanism

    • Substrate binding applies stress, distorts bonds
    • Lowers activation energy needed for reaction
  • Example: Carbonic anhydrase enzyme

    • Without enzyme: 200 molecules/hour
    • With enzyme: 600,000 molecules/second

Enzyme Specificity

  • Highly specific to substrates
  • Enzymatic activity involves formation of products from substrates
  • Example: Sucrase breaks down sucrose into glucose and fructose

Factors Affecting Enzyme Activity

  • Concentration: Rate depends on substrate and enzyme concentration

  • Temperature:

    • Increases rate up to an optimal point
    • Too high temperatures = denaturation
    • Human enzymes: Optimal around 35-40°C (98.6°F)
    • Some enzymes in extremophiles have higher optimal temperatures
  • pH:

    • Optimal pH usually 6-7
    • Activity decreases in very acidic or basic conditions

Enzyme Inhibitors

  • Types of Inhibitors

    • Competitive: Compete with substrate for active site
    • Non-competitive (Allosteric): Bind to different site, causing enzyme shape change
  • Impact: Inhibitors decrease enzyme activity

Conclusion

  • Enzymes are crucial for efficient biochemical reactions
  • Important to understand environmental factors affecting enzyme activity
  • Next lecture will continue with Chapter 6 and cover Chapter 7