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