Lecture on Biochemistry of Metabolism

Introduction and Logistics

• Instructor: Matt Vanderheiden
• Course: 705 (Biochemistry of Metabolism)
• Focus: Metabolism: what it is, why it's important
• Relevance: Important for med school (MCAT exams) and broader biology fields (medicine, ecology, evolution, engineering)

What is Metabolism?

• Definition: Chemical reactions that cells use to extract energy from the environment and synthesize macromolecules
  • **Functions: **Extract energy from environment and synthesize macromolecules
  • Importance: Understanding metabolism helps in better understanding food, health claims, medicine, agriculture, biofuels, etc.

Complexities of Metabolism

• Metabolic Pathway Chart: Hundreds of enzymes, complex pathways
• Goal: Understand key reactions and principles, not memorize the chart
• Key Principle: Common principles across all species, chemistry repurposing

Key Concepts

Sugar and Carbohydrates

• Sugars and Carbohydrates: Key energy transduction molecules
• Goal: Understand breakdown of sugars, energy release, and support for cell functions
• **High-Level Concepts: **
  • Anabolism: Building stuff (requires energy)
  • Catabolism: Breaking stuff down (releases energy)
  • Importance of Energy: Even when inactive, we need energy to sustain life
• Thermodynamics: Life maintains order in face of increasing entropy (Second Law of Thermodynamics).
• Catabolism in Humans: Constant catabolism required for cell viability (food and oxygen delivery)

Carbohydrates and Polysaccharides

• Monosaccharides: Can be reducing sugars
• Disaccharides: Some can be reducing depending on bond type (e.g., maltose, lactose)
• **Starch and Glycogen: **
  • Starch: polymer of maltose
  • Glycogen: highly branched, efficient energy storage in animals
• Cellulose: Beta 1-4 linkages, flat structure (structural polymer in wood)
• Chitin and Cartilage: Polymers with beta linkages (structural relevance)

Bioenergetics and Metabolism

What is Biological Energy?

• Common Misconception: Simply ATP, but deeper understanding required
• High-Level Thermodynamics: How energy is transduced in biological systems
• **Delta G (Gibbs Free Energy): **Determines reaction spontaneity.
  • Delta G < 0: Reaction is spontaneous
  • Delta G = 0: Reaction is at equilibrium
  • Delta G > 0: Reaction is not spontaneous

Glycolysis and Energy Extraction

• Burning Glucose: Energy release through stepwise oxidation
• **Key Reactions and Pathways: **Profitable under biologically acceptable conditions.
• **Example Energy Reactions: **
  • ATP Hydrolysis: Coupled to unfavorable reactions to make them favorable
  • Polymer Building (DNA, RNA, Proteins): Use energy from ATP hydrolysis (ATP -> AMP + 2 Pi)

Coupling Reactions in Pathways

• Reaction Coupling:
  • Combining two reactions to drive a non-spontaneous reaction forward (e.g., glucose to glucose phosphate)
  • Understanding pathway favorability depends on overall delta G
• **Key Equations: **
  • Delta G = Delta G naught prime + RT ln(Products/Reactants)
  • Pathways Favorable: If overall Delta G is less than zero, entire pathways can be driven.

Summary

• Metabolism Fundamentals: Understanding core principles to tackle complex bioenergetic problems and pathways.
• Importance of Conditions: Reaction conditions, equilibrium constants, concentration ratios, and overall energy balance determine spontaneous reactions.
• ATP Role: Integral in driving and coupling reactions to sustain life processes.

Next Lecture Preview

• Focus: Deeper into thermodynamics of metabolic reactions and the broader role of ATP.