igure 5. 4 The arginine molecule in a zwitterion stable structure 2. Energy Conservation In any chemical reaction as in all physical processes, total energy must be conserved Reactions in which the summation of the strengths of all the chemical bonds in the reactants exceeds the sum of the bond strengths in the products are termed endothermic. For such reactions, energy must to provided to the reacting molecules to allow the reaction to occur Exothermic reactions are those for which the bonds in the products exceed in strength those of the reactants For exothermic reactions, no net energy input is needed to allow the reaction to take place. Instead, excess energy is generated and liberated when such reactions take place. In the former(endothermic)case, the energy needed by the reaction usually comes from the kinetic energy of the reacting molecules or molecules that surround them. That is thermal energy from the environment provides the needed energy. Analogously, for exothermic reactions, the excess energy produced as the reaction proceeds is usually11 2.546 1.740 1.705 Figure 5.4 The arginine molecule in a zwitterion stable structure. 2. Energy Conservation In any chemical reaction as in all physical processes, total energy must be conserved. Reactions in which the summation of the strengths of all the chemical bonds in the reactants exceeds the sum of the bond strengths in the products are termed endothermic. For such reactions, energy must to provided to the reacting molecules to allow the reaction to occur. Exothermic reactions are those for which the bonds in the products exceed in strength those of the reactants. For exothermic reactions, no net energy input is needed to allow the reaction to take place. Instead, excess energy is generated and liberated when such reactions take place. In the former (endothermic) case, the energy needed by the reaction usually comes from the kinetic energy of the reacting molecules or molecules that surround them. That is, thermal energy from the environment provides the needed energy. Analogously, for exothermic reactions, the excess energy produced as the reaction proceeds is usually