Proteins Health Article

Definition

Proteins are linear chains of amino acids connected by chemical bonds between the carboxyl group of each amino acid and the amine group of the one following. These bonds are called peptide bonds, and chains of only a few amino acids are referred to as polypeptides rather than proteins.

Description

Proteins are all around us. Much of the body's dry weight is protein; even bones are about one-quarter protein. The animals we eat and the microbes that attack us are likewise largely protein. The leather, wool, and silk clothing that we wear are nearly pure protein. The insulin that keeps diabetics alive and the "clot-busting" enzymes that may save heart attack patients are also proteins. Proteins can even be found working at industrial sites—protein enzymes produce not only the high-fructose corn syrup that sweetens most soft drinks, but also fuel-grade ethanol (alcohol) and other gasoline additives.

Within our bodies and those of other living things, proteins serve many functions. They digest foods and turn them into energy; they move our bodies and move molecules about within our cells; they let some substances pass through cell membranes while keeping others out; they turn light into chemical energy, making both vision and photosynthesis possible; they allow cells to detect and react to hormones and toxins in their surroundings; and, as antibodies, they protect our bodies against foreign invaders. There are simply too many proteins—possibly more than 100,000—to even consider mentioning them all.

Proteins are made up of separate compounds called amino acids. It is these amino acids that our bodies actually need, not the entire protein molecule. Some amino acids are essential—they must be obtained from diet because they cannot be synthesized by humans in adequate amounts. There are nine essential amino acids. Others are nonessential, because they can be made in the body from precursors (components) of other amino acids. There are eleven nonessential amino acids.