We have heard much about protein during the last few years - how benefits accrue when we shift our diets away from too high a percentage of carbohydrates and fats. Yet, despite a deluge of popular books attempting to explain the science behind a high-protein diet, little light has been shed, and much confusion remains.
The human body contains at least 50,000 different kinds of proteins, each one serving a specific biological function. Among the different categories of proteins are enzymes, hormones, antibodies, transporters, and structural, supporting, and contractile proteins. They are the principal constituents of the protoplasm of all cells and are involved in virtually every vital process.
Proteins are large, highly complex organic molecules consisting of one or more polymeric chains of amino acids. There are twenty different kinds of amino acids commonly found in human proteins (over a hundred are known, however), and in each protein they exist in a unique, genetically determined sequence, typically several hundred units in length. The amino acid chains twist and fold upon themselves in a characteristic manner that determines the molecule's exact size and shape - and it is the size and shape, as well as the chemical properties of the constituent amino acids, that determine the protein's function and biological activity.
When we eat plant or animal proteins, digestive juices in our stomach and small intestine break them down, initially to smaller amino acid chains called peptides or polypeptides, and ultimately to individual amino acids. These small molecules can pass through the gut into the bloodstream and are carried to all our cells, where they are reassembled into human proteins under the direction of life's master molecule, DNA.
All proteins are not alike, especially with regard to their energy value. Owing to their different molecular shapes and compositions, different proteins are digested at different rates, and they produce different "brews" of amino acids to deliver to the body's cells for protein synthesis and other vital functions. Thus, certain nutrient proteins can provide more energy, faster appetite satisfaction, and heightened mental activity.
This page created September 4,
2002 and last updated
November 05, 2007
Web hosting by The Duncans
FastCounter by bCentral