Chemistry and Physics Laws Governing Reactions:
When examining metabolism and metabolic processes there are two distinct laws that govern reactions that must be remembered at all times. These laws govern the movement of atoms and materials within reactions and the energy flow through the cell (or tissues) during the metabolic processes of the cell. Further, these will explain why some molecules will be considered as being a product of a reaction versus a byproduct of the reaction. Likewise, these laws help explain how the body’s heat is produced through combining the energy loss from the reactions (chemical or mechanical) of the body necessary to maintain homeostasis.
The first comes to us from chemical reactions that stipulate mass of products must come from the mass of the reactants and that all mass from reactants must go to something in the products. This is the law of conservation of mass. In which it is stated that mass can never be created nor destroyed, it will only change the molecular form of that mass. Secondarily, the amount of individual elements at the start of any reaction must equal the amount of that individual element at the end reaction. From this idea, any molecule that can be generated from a reaction that is not itself a product from the reactants is therefore a byproduct of the reaction. A phenomenon that will be examined in the energetic pathways related to regeneration of adenosine triphosphate (ATP) within pathways of glycolysis, the Krebs’ (citric acid) cycle, or the electron transport chain.
The next set of laws dictates the means by which energy can be used by the cells within the metabolic processes. These are the laws of thermodynamics. In which we must remember two principal statements that come from the first law and the third law. Where, it is key to remember that energy can never be created nor destroyed. Energy can only be converted from one form (i.e. chemical potential) to another form (i.e. mechanical kinematic) allowing work to be performed. Secondly, this conversion of energy between forms is never complete (i.e. 100%) in the transfer. Meaning that in normal states the end result will have less total energy within it after conversion than prior to the conversion. Most of the loss of energy for the body is through the generation of heat (thermogenesis) that is then lost the tissues and fluids surrounding the cells that are metabolically active. The proportion of energy loss during the transfer within the metabolic pathways dictates the efficiency of the pathway.