GLOSSARY

Quaternary Protein Structure describes assembly of multiple protein subunits. It applies to multisubunit structures and is not present in every protein.

Sequence, local chain shapes, a chain's three-dimensional arrangement and assembly of subunits are different structural descriptions. Not every protein has multiple subunits. These are not four food types; after digestion, amino acids can build new proteins with different sequences and functions rather than reproduce the original food protein intact.

Many protein functions depend on suitable arrangement and interactions within a chain; the environment and helper proteins can influence folding. Not all proteins have one completely fixed shape throughout. Understanding biological structure does not establish that the same intact structure must be eaten or preserved through digestion to obtain amino acids.

Common protein amino acids use amino and carboxyl groups in the chain backbone, while side chains create differences. Charge depends on the environment and pH; a neutral textbook drawing is not always the dominant bodily form. A chemical-group name alone establishes neither an ergogenic effect nor a supplement's nutritional value.