Energy interconversion

Figure 1 is an early representation of these three regimes with their distinctive physical and chemical phenomena (3). In this early picture, energy interconversion was considered as a form of isomerization—"energy isomerization"—leading to an expression of the excitation in a form more or less independent of the type of energy input. Vibrational excitation, especially of the lower frequency modes corresponding to intermolecular motion, was considered as the basis for desorption. Activation of surface phonons expresses these ideas in different currency. 

Second-law thermodynamic analyses have been shown to be of considerable value when applied to systems where an efficient energy interconversion is important. Using the chemical energy transport systems as examples, the use of exergy ratios as a measure of thermodynamic quality has been shown to give Important Insights Into the efficiency or inefficiency inherent in any conversion of one energy form to another. 

As mentioned above, polymorphism may also arise for compounds formed by isomers whose structures are related by low-energy interconversion pathways, e.g. cluster carbonyls with different distributions of bridging and terminal ligands, or substituted metallo-arenes and metallo-cyclopentadienyl complexes [60]. In such cases, the structural isomers correspond to different energetic minima along the interconversion pathway and the cohesion of the respective crystals may stabilize the less thermodynamically stable isomers. Crystals of structural isomers may (or may not) interconvert via a phase transition. 

Guimaraes-Motta H, Sande-Lemos MP, Mrid LD. 1984. Energy interconversion in sarcoplasmic reticulum vesicles in the presence of Ca2+ and SC+ gradients. J Biol Chem 259(14) 8699-8705. 

Bering, C. L. Energy Interconversions in Photosynthesis. J. Chem. Ed. 62, 659-664 (1985). [A discussion of basic concepts of photosynthesis, concentrating on the light reactions and photosystems.]... 

List examples of energy conversions by proton gradients and appreciate their central roles in free-energy interconversions. 

As discussed later, the influence of conformational isomerism, which involves the low energy interconversion of stereoisomers, on lipophilicity depends on the formation of internal H bonds, hydrophilic and hydrophobic folding, and proximity effects between polar and nonpolar groups. 

There are two aspects of bioenergetics that we want to emphasize at the end of this article. These are the dependence of life on photosynthesis and the diversity of energy interconversions in living systems. 

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