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Explain why the structure and function of proteins is essential to living organisms.

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Explain why the structure and function of proteins is essential to living organisms. Proteins, along with carbohydrates, lipids and nucleic acid make up all life on earth, and without any one of these macromolecules, life on earth would not be able to continue. Proteins consist of amino acids joined together via peptide bonds to form polypeptides. There are 20 natural amino acids without which proteins couldn't exist. COOH | H-C-R | NH2 Above is the general structure of an amino acid, the R represents the variable group, which varies with each amino acid, and affects the properties and behaviour of each amino acid. To form a protein the amino acid must bond with at least one other amino acid, forming a peptide bond. As shown in the diagram Amino acids bond to form proteins which can bond with other amino acids or other proteins to form new proteins, therefore there is an infinite number of proteins which can be formed, each one having its own structure and function within living organisms. (1) (2) (3) There are four levels of construction within proteins and which level the protein is at determines the structure and function of that particular protein. The four levels are: Primary, Secondary, Tertiary and Quaternary. ...read more.


The new 3D shape, which is roughly spherical, is caused by projecting variable groups running down the polypeptide backbone interfering with the alpha helix and beta pleating arrangements of secondary structure proteins and forming bonds, such as hydrogen, ionic and di-sulphide bonds, with each other. This causes the molecule to twist and form into a 3D roughly spherical arrangement. Quaternary structure is when more than one polypeptide chain bond to form a large protein molecule. Quaternary proteins make up the majority of metabolically active proteins. Such as haemoglobin, found in the blood and used to carry chemicals, i.e. oxygen, round the body. Tertiary and Quaternary structure proteins tend to be globular proteins, and have a metabolic function, such as: Hormones, antibodies, and enzymes. Enzymes are present in all living organisms and are described as biological catalysts as they speed up chemical reactions (i.e. the bonding or splitting of molecules) with living organisms. These are essential to all life as without enzymes simple reactions such as digestion and respiration would be so slow that most if not all life would die off. (8) (9) Enzymes are stereo specific, and so only catalyse one specific substrate. This is explained using the lock and key theory, where the enzyme molecule temporarily bonds to the substrate, via certain atoms on the protein which are placed in the exact place to bond to the substrate; these are known as active sites. ...read more.


Each hormone is specific to certain receptor sites around the body, be it near hair follicles or on the lining of the heart, this is due to the structure of the protein only 'fitting' that particular site, similar to the lock and key theory. It is possible to de-nature all globular proteins because they are susceptible to heat, pressure and acidity. If the temperature rises excessively or the globular protein is put under immense pressure kinetic energy within the molecule will increase causing vibrations within the molecule to increase also. Eventually the hydrogen bonds holding protein in its 3D shape break irrevocably causing the molecule to 'unfold' and lose its shape. Also excess acidity causes the hydrogen bonds to break and has the same effect as excess heat. This is known as de-naturation of the protein. When this happens the proteins can no longer perform their functions because they no longer have the structure to do so; the key no longer fits the lock. This further proves a direct link between structure and function in that when the structure is proved even minutely, the protein can no longer carry out its metabolic function. Matt Wilkinson Matt Wilkinson 1 Biology Richard Pim ...read more.

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