U1L8 - Bioenergetics

Bioenergetics Overview

• Energy Definition: Energy required to do work.

• Types of Energy:

  • Potential Energy: Energy stored in bonds; if released, can do work (e.g., chemical potential energy).

  • Kinetic Energy: Energy of movement.

• Energy Conversion:

  • Potential energy can convert into chemical or kinetic energy.

• Energy Sources:

  • Most energy on Earth comes from the sun.

• Cellular Energy:

  • Glucose stores significant energy (2831 kJ/mol).

  • Cellular work uses much less energy (~30 kJ/mol).

  • Cellular respiration breaks glucose to transfer energy into more manageable forms.

Thermodynamic Laws

• First Law: Energy cannot be created/destroyed, only converted.

• Second Law: Energy use leads to increased entropy (disorder); energy becomes less available after work is done.

Metabolism and Reactions

• Metabolism: Encompasses all reactions for sustaining life.

• Types of Metabolic Reactions:

  • Catabolism: Breakdown of molecules, releasing energy.

  • Anabolism: Synthesis of larger molecules, requiring energy.

• Bond and Free Energy:

  • Bond Energy: Energy to form/break chemical bonds.

  • Free Energy: Energy available to do chemical work.

Gibbs Free Energy

• Endergonic Reactions:

  • Non-spontaneous (G > 0).

  • Energy absorbed.

• Exergonic Reactions:

  • Spontaneous (G < 0).

  • Energy released.

• Examples:

  • Water does not spontaneously break down into hydrogen and oxygen due to positive free energy.

  • Reverse reaction (2H2 + O2 → 2H2O) releases free energy (-468 kJ/mol) and is spontaneous.