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.
- R groups of a few of the amino acids that make up the active site catalyzed the conversation of substrate to product, and the product departs from the active site. Enzymes use a variety of mechanism that lower activation energy and speed up a reaction. 1. First, in reactions involving two or more reactants, the active site provides a template on which the substrate can come together in the proper orientation for a reaction to occur between them.