Lecture Notes on Metabolism

Introduction to Metabolism

• Metabolism: Totality of an organism's chemical reactions.
• Future lectures will cover:
  • Cellular respiration: how cells derive energy from sugars.
  • Photosynthesis: how plants store energy from light.
• Cells as chemical factories:
  • Example: Sodium-Potassium ATPase: pumps ions while expending ATP.
  • Bioluminescence in firefly squids for mating and predator deterrence.
• Metabolism involves extracting stored energy from sugars and fuels.

Pathways in Metabolism

• Catabolic Pathway: Breakdown molecules, releases energy. Example: Cellular respiration.
• Anabolic Pathway: Builds larger molecules, consumes energy. Example: DNA synthesis from nucleotides.

Bioenergetics

• Study of energy flow in living organisms.

Understanding Energy

• Energy: Capacity to cause change.
• Two forms:
  • Kinetic Energy: Energy of movement (e.g., thermal energy, light energy).
  • Potential Energy: Energy due to location or structure (e.g., water behind a dam, chemical bonds).
• Energy transformation: Conversion between kinetic and potential energy.

Thermodynamics

• First Law: Energy can be transferred or transformed but not created or destroyed.
• Second Law: Every energy transfer increases the entropy (disorder) of the universe.
• Entropy: Measure of disorder; spontaneous processes increase entropy.

Gibbs Free Energy

• Defines the portion of a system's energy available to perform work.
• Delta G (ΔG): Change in free energy, predicts spontaneity of a process.
  • Negative ΔG: Spontaneous process.
  • Positive ΔG: Non-spontaneous.
• Equilibrium: Lowest free energy state, no work can be done.

Types of Reactions

• Exergonic Reactions: Release energy (negative ΔG), spontaneous.
• Endergonic Reactions: Absorb energy (positive ΔG), non-spontaneous.

Cells and Energy

• Cells operate as open systems with constant inflow and outflow, preventing equilibrium.
• Types of Cellular Work:
  • Chemical Work: Reactions.
  • Transport Work: Moving substances (e.g., sodium-potassium pump).
  • Mechanical Work: Movement (e.g., muscle contraction).

Energy Coupling and ATP

• ATP (Adenosine Triphosphate): Key molecule in energy transfer.
  • Hydrolysis of ATP releases energy (exergonic).
  • Energy coupling: Uses energy from ATP hydrolysis for work (chemical, transport, mechanical).
• ATP regeneration from ADP using energy from catabolic reactions.

Conclusion

• Overview of metabolism and introduction to bioenergetics principles.
• Future lectures will focus on specific metabolic pathways like cellular respiration and photosynthesis.