A chemical reaction is the forming and breaking apart of chemical bonds that hold atoms, molecules and chains of molecules together. In organisms, such as human beings, these chemical reactions can take place inside of the body and are necessary for the organisms to live. As chemical bonds break, they release energy, which is then used to sustain bodily functions.
Combustion and Cellular Metabolism
Metabolic reactions are chemical reactions that occur within the body to release useable energy. An example of a metabolic process is cellular metabolism. During cellular metabolism, the molecule glucose combines with oxygen and reacts to form carbon dioxide and water, as well as ATP, which is a form of energy that the body can use for its functions. The carbon dioxide is expelled through exhalation and the water is absorbed into the bloodstream. This is an example of a combustion reaction.
Entropy is defined as a degree of chaos or disorder. It can also refer to a degree of randomness. Because organized and ordered structures, like cells, naturally become disordered as time passes, chemical reactions occur to restabilize the cells. When a reaction occurs and heat is released, heat adds to entropy because it is random energy. Thus, a reaction such as the combining of molecules A and B will form products C and D and the products will be less entropic than the molecules used to form them because they have released heat.
Synthesis and Decompostion
A synthesis reaction within the body occurs when simple molecules join together to form a much more complicated molecule. An example of this sort of reaction is when iron and sulfur combine to make iron sulfide. Decomposition is a reaction that occurs when a complex molecular structure within the body is broken down to produce two simpler molecules or atoms. An example of this is when water is broken down to form hydrogen and oxygen.
Single and Double Displacement
Single displacement is a chemical reaction that occurs when elements or molecules switch places and thus form new compounds. The rearrangement of the molecules means that no element is lost, only matched differently. An example is when magnesium and the hydrogen in water trade places to form the compounds magnesium hydroxide and hydrogen. Double displacement is when two elements or molecules switch places instead of one.