Peptides aren't technically identical to proteins, but the words are used more or less interchangeably in common parlance. You need proteins in your diet and in your body for a variety of reasons. In the diet, they serve as a source of building blocks and energy, whereas in the body, they perform a variety of functions.
Peptides and Proteins
Peptides are large molecules made up of long chains of smaller building blocks called amino acids. While peptides can be any length -- some are as short as just a few amino acids long, whereas others contain hundreds of amino acids -- they're all made up of different combinations of 20 naturally occurring amino acids. The difference between a peptide and a protein is that a protein has been folded into a three-dimensional structure, but in common parlance you'll generally hear "peptide" and "protein" used to mean the same thing.
Benefits of Structural Peptides
In your body, you depend upon peptides as major structural components of cells and extracellular tissue. In fact, your cells consist largely of protein. Structural proteins connect cells to one another and form a stable matrix for body tissues and organs. For instance, your skin has elasticity and durability because of the structural protein collagen. Another structural protein, called keratin, forms your hair and fingernails, explains Dr. Lauralee Sherwood in her book "Human Physiology." There are also many structural proteins inside cells.
Benefits of Functional Proteins
In addition to serving structural roles, peptides have many different functions in the body. Cells have receptors on their surfaces that allow them to communicate with one another and to respond to molecules in their environment, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry." These receptors are peptide-based. Some communication molecules, like the hormone insulin, are also peptides. Peptides form large portions of cellular machinery, such as the ribosomes that help express a cell's genetic information.
Peptides in the Diet
You need peptides in the diet for several reasons. First, when you consume protein, you digest the peptides into their constituent amino acids, which you then absorb into the bloodstream. The amino acids serve as building blocks for the cells to use in making their own peptides. Your cells can also burn amino acids for energy -- they contain the same amount of energy per gram as such carbohydrates as starch and sugar.
References
- "Biochemistry"; Reginald Garrett, Ph.D., and Charles Grisham, Ph.D.; 2007
- "Biochemistry"; Mary Campbell, Ph.D., and Shawn Farrell, Ph.D.; 2005
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