Bioenergetics concepts

What you will learn

• Define system, environment, energy, entropy, and enthalpy in the cellular context.
• Use ΔH, ΔS, ΔG, and Keq to predict reaction spontaneity, direction, and reversibility.
• Explain the additivity of ΔG and coupling an endergonic reaction to an exergonic reaction.
• Relate redox potential, electron transfer, and free-energy change.
• Identify high-hydrolysis-potential bonds and the central role of ATP.
• Recognise the main energy-production pathways of energy metabolism.

Course outline

1. The cell as an energy system

   Connect matter inputs, metabolic reactions, and the forms of energy that a cell can use.

   8 min

2. Defining a system and recognizing energy

   Define the system under study, its exchanges with the environment, and the main forms of energy.

   12 min

3. First law: internal energy, enthalpy, and Hess's law

   Track heat and work exchanges while keeping the conservation of energy in view.

   15 min

4. Second law: entropy and dissipation

   Understand why part of the energy becomes unavailable for useful work during a spontaneous transformation.

   10 min

5. Gibbs free energy and reaction direction

   Isolate the energy available for work and predict the thermodynamic direction of a reaction.

   12 min

6. Standard state, actual energy, and equilibrium constant

   Move from the standard reference to cellular concentrations and relate ΔG°′ to Keq.

   18 min

7. ΔG additivity and reaction coupling

   Pair a favorable reaction with an unfavorable one to make a metabolic step possible.

   13 min

8. Redox: donor, acceptor, and redox couples

   Break a redox reaction into two half-reactions and follow the electron transfer.

   12 min

9. Redox potential, free energy, and the Nernst equation

   Compare the electron affinity of couples and relate redox potential to ΔG under actual conditions.

   18 min

10. Energy-rich compounds and ATP

    Relate high-energy hydrolysis bonds to ATP's role in cellular coupling.

    17 min