Lecture on Thermodynamics and Metabolism

Introduction

• Thermodynamics is central to understanding metabolism.
• Biologists need to understand physics principles as they are biochemical reactors governed by physics.

Laws of Thermodynamics

First Law

• Energy Conservation: Energy in the universe is constant.
  • Energy cannot be created or destroyed.
  • The total amount of energy from the Big Bang remains unchanged.

Second Law

• Energy Conversion: Less energy is available after conversion in a system.
  • When energy changes state, the system loses energy available for work.
  • Example: Engines cannot operate perpetually.

Concept of Energy

• Energy Definition: Ability to do physical work.
  • Work involves force applied across a distance.
  • No work is done if there is no displacement (e.g., holding a stapler steady).

Misconceptions about Energy

• Energy is not a physical substance or aura.
• It's an abstract concept, calculated in physics equations.

Forms of Energy

• Potential Energy: Energy stored (e.g., gravitational, chemical).
• Kinetic Energy: Energy of motion (e.g., mechanical, thermal).
• Electrical/Electromagnetic Energy: Vital in physiological processes.

Metabolism and Energy

• Metabolism involves converting chemical potential energy into other forms.
  • Example: Walk converts chemical to mechanical energy.
  • Plants convert light to chemical energy.
• Must adhere to the laws of thermodynamics.

Understanding Entropy

• Entropy Definition: Energy in a system unusable for work.
  • Increases with system state changes.
• Gibbs Free Energy: Energy available to do work.
  • Decreases as entropy increases.

Degrees of Freedom and Entropy

• System's entropy is proportional to its degrees of freedom.
  • More degrees of freedom = more entropy.

Illustrations

• Example: Water behind a dam demonstrates potential energy.
• Cats exhibit kinetic and chemical potential energy.
• Entropy demonstrated with objects showing degrees of freedom.

Conclusion

• Metabolism is managing energy states, following thermodynamic laws.
  • Closed systems can't decrease total degrees of freedom when changing state.
• Future studies will explore energy transfers without violating these principles.