Proteins are the most complex and functionally diverse molecules of living organisms, consisting of long chains of amino acids, these acids link in various ways to form many different proteins. Proteins differ from carbohydrates and fats given that they contain nitrogen in addition to carbon, hydrogen and oxygen. The monomers of proteins are twenty naturally-occurring amino acids, the polymer is the polypeptide chain created by the amino acids bonding together. A typical protein involves one or more polypeptide chains which fold into a unique functional protein. Each amino acid has a NH2 amino group and a COOH carboxyl group as shown:
Amino acids bond together to form proteins in much the same way that monosaccharide sugars unite to form polysaccharides, by the process of condensation, the bond that holds them together is called the peptide bond. As shown below:
Primary, secondary, tertiary and quaternary structures are terms used in describing the structure of proteins. Primary structure is the chain of amino acids of which the polypeptides are comprised. S Secondary structure is the basic form the chain of amino acids takes on, of which there are two forms: α – helix and β – pleated sheet which can be seen in the diagram. α – helix: is a spiral structure like a spring, there are many hydrogen bonds which make it strong in addition to being flexible. β – pleated sheet: is made up of side by side chains connected by hydrogen bonds making it very stable.
The tertiary structure is the 3-D shape of the protein and the way the helically coiled chains and pleated sheets are folded together. Ionic bonds between positively and negatively charged side chains help give the protein a stable shape. If a protein consists of several polypeptide chains the way they arrange themselves is quaternary structure, each protein created has a precise and specific shape.
There are two groups proteins fall into:...
Bibliography: Biology A-level: Biological Molecules and Enzymes, (2000), Available: <http://www.s-cool.co.uk/alevel/biology/biological-molecules-and-enzymes/proteins.html>, [Accessed 25/10/10].
Proteins, (2002), Available at: <http://www.contexo.info/DNA_Basics/Protein_Structure.htm> [Accessed 25/10/10].
Roberts, MBV (1986), Biology a functional approach, 4th ed. Surrey, Nelson. p72-79.
<www.cornellbiochem.wikispaces.com>, image, [Accessed 25/10/10]
<www.uvmbiology1.blogspot.com>, image, [Accessed 25/10/10]
<www.biology.lsu.edu>, image, [Accessed 25/10/10]
<w3.hwdsb.on.ca>, image, [Accessed 25/10/10]
<kvhs.nbed.nb.ca>, image, [Accessed 25/10/10]
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