Lecture Notes: Metabolism and Energy in Cells

Overview of Metabolism

• Definition: Metabolism - all chemical reactions in an organism.
• Function: Transforms matter and energy, adhering to thermodynamics laws.
• Pathways:
  • Catabolic Pathways: Release energy by breaking down complex compounds (e.g., cellular respiration).
  • Anabolic Pathways: Consume energy to build complex molecules from simpler ones (e.g., synthesis of proteins).

Bioenergetics

• Definition: Study of energy flow through living organisms.
• Energy Forms:
  • Kinetic Energy: Related to motion, e.g., thermal energy.
  • Potential Energy: Due to location/structure, e.g., chemical energy.
• Energy Conversion: Energy can be transformed from one form to another; subject to thermodynamic laws.

Thermodynamics

• First Law: Energy can be transferred/transformed, but not created/destroyed (Conservation of Energy).
• Second Law: Energy transfers increase universe's entropy; some energy lost as heat.

Free Energy and Spontaneity

• Free Energy: Capacity to do work, tendency to move to a more stable state.
• Delta G (ΔG): Change in free energy;
  • ΔG < 0 indicates a spontaneous reaction.
• Equilibrium:
  • Systems do work only when moving towards equilibrium.
  • Spontaneous changes decrease free energy and increase stability.

Reaction Types

• Exergonic Reactions: Release free energy, spontaneous.
• Endergonic Reactions: Absorb free energy, non-spontaneous.
• Equilibrium in Cells:
  • Living cells are open systems, not at equilibrium.
  • Metabolism constantly drives reactions away from equilibrium to sustain life.

Energy Transformation in Cells

• Cells maintain non-equilibrium states to perform work continuously.
• Analogy: Open hydroelectric systems model cellular processes better than closed systems.

Conclusion

• Metabolism in cells involves a controlled series of reactions, crucial for energy management and cellular function.
• Further exploration of catabolic pathways and their role in energy release will continue in the next chapter.