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How does the Primary Structure of a Protein dictate its overall Structure and Function?

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How does the Primary Structure of a Protein dictate its overall Structure and Function? Proteins are extremely important biological compounds. They are the biggest molecules in cells, with over 50% present in one cell, compared to only 20% RNA and 3% DNA. Proteins decipher the information which is encoded in genes and work to successfully carry the resultant instructions out. The real marvel is that there is no limit to the number of proteins; they are determined by amino acids and in the structure of amino acids, there is an R-group which determines the type of the amino acid. This R-group has 20 different varieties which can all attach themselves to the amino acids. Then these amino acids can be attracted and bonded to other amino acids with different R-groups. As is becoming increasingly evident, it can be seen that the number of possible combinations is almost infinite. The ways proteins are actually formed are as follows: One amino acid joins to another amino acid which joins to another amino acid and so on until there is a chain of amino acids, which is known as a polypeptide. The name comes from 'poly' meaning 'many' and 'peptide' which is the name of the bonds between each of the amino acids. This peptide bond is formed, as can be seen on the diagram, between the amine group (NH2) ...read more.


They are weak attractions between the non-polar side groups. The structure of a tertiary protein is also affected by the hydrophobic attractions or exclusions; if an atom is hydrophobic, it will face inwards and away from any water-based environment. After all of these bonds and interactions have had an effect, the polypeptide chain looks like this: Finally, the quaternary structure of a protein makes the polypeptide chain in to a 'proper' protein. This involves usually more than one polypeptide chain joining together, along with prosthetic (non-protein) groups to make an overall protein molecule. The way these polypeptides are joined together is similar to the tertiary structure except that instead of the bonds being formed with amino acids of the same polypeptide chain, they are formed with other chains. An example of a prosthetic group is iron, in haemoglobin which is very important in determining its structure and therefore its function. Another example of a prosthetic group is glucose in the protein miraculin. This is named as such because of its ability to make any sour or bitter substance taste sweet. There are two main categories of proteins in this section: fibrous and globular proteins. Fibrous proteins normally have structural functions as they are formed by long, parallel chains which are linked by cross-bridges. An example of this is collagen, used in tendons and keratin, used in hair. ...read more.


This makes sure that the cells remain stable and as the fibrils act like strong covalent bonds, the structure is held together powerfully. Collagen is only a polymer; it is actually made up by lots of molecules called tropocollagen. They are approximately 300 nm in length and 1.5nm in diameter. They are formed from three polypeptide strands called alpha polypeptides. As collagen contains millions of strands of tropocollagen and they are all covalently bonded, you begin to get the idea of its strength. Indeed, a single collagen fibre of 1mm diameter has the ability to support a mass of 10kg if not more before it finally breaks. This is why it is so useful in the human body; a massive amount of exertion is needed before it breaks and causes damage. In conclusion, it can be seen that the primary structure is essential in determining the structure and function of a protein. If the amino acids did not bond in the exact required order, then the protein would fail to work correctly and hence all of the other structures would also fail. Therefore, it is imperative that the primary structure is correct for the rest of the protein to work, even though it is comparatively very simple. Furthermore, it can also be seen that although some proteins do not have secondary or quaternary structures, they must have a primary structure, further highlighting its importance for proteins. ?? ?? ?? ?? Osama Hamid L2 ~2400 Words ...read more.

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