Topics selected to be covered include thermodynamics: Definition of system and surroundings, Energy, work and heat. The First Law of Thermodynamics, Hess’s law, enthalpy of reactions. Spontaneous changes: Entropy / Free Energy. The second law of thermodynamics, free energy changes and equilibrium constants will be discussed.  The principles of thermodynamics and their application to the energetics of the cell will also be discussed. There will be a review of the structure of mitochondrion and chloroplast and their relationship to the redox complexes of their respective electron transport system. The review will also include the link between ATP synthesis and sources of energy establishment of proton gradients, the concept of high energy compounds, the redox systems, and energetics of coupled reactions. ATP utilisation for the performance of cellular work, active membrane transport, activation for metabolism, and muscle contraction will be examined.