You might see the word alloy described as a mixture of metals, but that's a little bit misleading because some alloys contain only one metal and it's mixed in with other substances that are nonmetals (cast iron, for example, is an alloy made of just one metal, iron, mixed with one nonmetal, carbon).
Energy substrates in the human body are either carbohydrates, fat or proteins. Protein degradation yields amino acid residues which can be converted to carbohydrates and used in energy production. Carbohydrates (sugars) and amino acids from proteins give approximately 4 kcal/gram dry weight when burned in the body.
NAD+ is also a substrate for several important biochemical reactions-histone/protein deacetylation by the Sir2 family of enzymes, ADP-ribosylation of proteins (for example those catalyzed by the PARPs), and formation of cyclic ADP-ribose (important for calcium signaling).