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.
Enzymes are said to be substrate specific. A substrate is a molecule that temporarily binds with the. enzyme at an area on the enzyme called the active site. Each enzyme catalyzes one specific reaction. because there is only one type of substrate molecule with the exact shape that will fit in the enzymeâs. active site.