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Proteins are the macromolecules of life. Discovered in 1838, proteins are recognized as a large number of superior organic compounds that make up living organisms and are essential to their functioning. The term protein comes from the Greek word “proteies” or “primary”. Proteins have many different properties and function in a variety of ways.

They can function as a building material, in teeth, bones and muscles, and they can serve as enzymes, hormones, and neurotransmitters. Its functions are the most diverse of any family.

Whether found in humans, animals, plants or in single-celled bacteria, proteins are made of units of 20 different amino acids. Proteins consist of macromolecules called polypeptides, made from monomers called amino acids. Proteins have hundreds, thousands, or sometimes even millions of these amino acids. These amino acids are made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Some proteins consist of only single polypeptides. In most cases it involves two or more combined polypeptides, sometimes with other small organic molecules or metal ions.

The most basic level of protein structure, called the primary structure, is the linear sequence of amino acids. Different sequences of the acids along a chain, however, affect the structure of a protein molecule in different ways. Protein’s secondary structure often contains long stretched out chains of amino acids called strands that line up together to make sheets. These are called beta strands and the sheets are called beta-pleated sheets. A protein may contain either or both alpha helices and beta pleated sheets. Alpha helices and beta pleated sheets are joined by less clear structures often grouped together under the name of coil. Some small proteins may be made of coil.

Shape is also important. Proteins are coiled and twisted, giving it a unique shape. The shape depends on the sequence of the amino acids, which can be hydrophilic or hydrophobic. Those that are hydrophilic want contact with water and will be twisted to maximize contact. Those that are hydrophobic are twisted in such a way to minimize contact. Changing one amino acid in the polypeptide sequence can destroy this shape and make the protein function improperly if not at all.

A very important function that proteins can serve are to act as catalysts. Enzymes are organic catalysts ma...

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... cells their shape and as well as parts of the linkages that stick cells together into tissues and organs. So, the sequence of amino acids in all proteins is genetically determined by the sequence of nucleotides in cellular DNA.

So basically Proteins are basic constituents in all living organisms. They are complex molecules composed of amino acid and necessary for the chemical processes that occur in living organisms. Proteins are sometimes referred to as macromolecular polypeptides because they are very large molecules and because the amino acids of which they are composed are joined by peptide bonds. The vast majority of the proteins found in living organisms are composed of only 20 different kinds of amino acids, repeated many times and strung together in a particular order. Each type of protein has its own unique sequence of amino acids. Also each protein makes every living organism different.


1. Proteins, Lexicon Universal Encyclopedia, 1989 Volume 15, pg.576.



4. “Proteins”. SceinceDaily.þ2000 þ

5. “Proteins”. Britannica Online 2000 þ
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