**2. Why a catalytic system is important for prebiotic chemistry?**

Before reviewing the state-of-art of mineral-catalyzed organic synthesis, larger questions here are: (1) Why catalysis is required for chemical evolution? (2) At which evolutionary period did catalysis begin to play an important role? The emergence of first life and the subsequent evolution from prokaryotes to eukaryotes all require wellregulated chemical conversion for efficient energy harvesting, sustainable supply of building blocks, and maintaining intracellular homeostasis. Eukaryotes developed more complex energy harvesting organelles that rely on respiration electron transfer chain and photosynthesis to metabolize with a higher transformation efficiency of energy and mass [32] (**Figure 2**). This is essential for maintaining their high cellular complexity in terms of both structure and functionality by balancing the enthalpy and entropy [36]. Notably, the enzymes responsible for these chemical conversions are catalytic, namely, the enzyme catalysts do not change chemically after one cycle or turnover of reaction, although enzymes indeed need replacement after the

### **Figure 2.**

*The scenario of co-evolved catalytic system and life. During the continuous evolution from geochemistry to biochemistry, and the evolution of eukaryotes from prokaryotes, the gradually evolving catalytic systems serve as the physicochemical and energetic basis for promoting an increased energy transduction efficiency and reaction activity for supporting the higher complexity of (proto-)metabolism or (cellular) structures. Schemes of prokaryotic and eukaryotic cellular structures are adapted from Ref. [33]. Schemes for the electron transfer chains in photosynthesis and respiration are adapted from Ref. [34] and Ref. [35], respectively.*

### *Minerals as Prebiotic Catalysts for Chemical Evolution towards the Origin of Life DOI: http://dx.doi.org/10.5772/intechopen.102389*

expiration of their lifetime. This catalytic feature is essential for boosting the reaction kinetics, saving energy for re-synthesizing enzymes, adapting to different substrate conditions, reversibly promoting both the two directions of the reaction, and so on [37]. As a comparison, in a non-catalytic, stoichiometric reaction, the active species that reacts with the geochemical substrates to target organics end up with a change in their chemical structures in an irreversible manner. After the complete consumption of the active species, the reaction can no longer proceed. From a top-down point of view, the prebiotic chemistry probably needs to evolve towards a catalytic, sustainable type of reaction network, to solve the problem of the shortage of supply of the building blocks/precursors, promote the reaction kinetics, and finally become self-independent when being encapsulated in a protocell. However, it should be noted that, at the initial stage of prebiotic synthesis, both catalytic and stoichiometric reactions are important for the synthesis of organic molecules to accumulate these organic precursors for subsequent conversion. As will be shown later, a large portion of prebiotic syntheses to date have been focusing on a stochiometric type reaction, therefore, relying on active agents. However, for some reason, the term "catalyst" has been used occasionally and misleading. In the following session, special care will be paid to differentiate the "catalytic" and "stoichiometric" types of reaction.
