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Overview of Metabolism

Overview of Metabolism

  • Metabolism encompasses all chemical reactions in an organism.

  • Understanding energy is key to understanding metabolism.

Key Concepts

  • Laws of Thermodynamics: 1st law (energy cannot be created/destroyed) and 2nd law (energy transfer increases entropy).

  • Energy Types: Kinetic vs. potential; free energy (usable) vs. other forms of energy.

  • Reactions: Some are spontaneous (occur without energy input), some favorable but non-spontaneous.

  • Energy Coupling: Catabolic reactions provide energy to drive anabolic reactions via ATP storage.

Energy Descriptions and Types

  • Kinetic Energy: Energy of movement, increases with temperature.

  • Potential Energy: Stored energy; includes gravitational and chemical potential energy.

Thermodynamics Laws

  • 1st Law: Energy can be transformed but not created or destroyed.

  • 2nd Law: Energy transfers increase entropy, which limits usable energy.

Reaction Spontaneity

  • Isolated systems require spontaneous reactions since no energy can enter.

  • Total energy in a system remains constant during reactions.

  • Entropy increases within isolated systems, reducing usable energy.

Biological Systems vs. Isolated Systems

  • Biological systems are open; they exchange energy and matter.

  • Living organisms maintain low entropy by increasing surrounding entropy.

Gibbs Free Energy

  • Total energy in a system: H = G + (T)(S) where H = total energy (enthalpy), G = free energy, T = temperature, S = entropy.

  • Changes in free energy during reactions: \Delta H = \Delta G + (T)(\Delta S).

Reaction Types

  • Exergonic Reactions: Gibbs free energy decreases; these are spontaneous (negative \Delta G).

  • Endergonic Reactions: Gibbs free energy increases; non-spontaneous (positive \Delta G).

Metabolic Pathways

  • Metabolic pathways convert substrates to products through enzyme-catalyzed steps.

  • Anabolic pathways require energy, are endergonic, and are not spontaneous.

  • Catabolic pathways release energy, are exergonic, and are spontaneous.

Energy Coupling and ATP

  • ATP is crucial for energy coupling: it transfers energy from catabolic reactions to anabolic processes.

  • Phosphorylation of molecules increases their free energy, enabling non-spontaneous reactions.