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Enzymes/Enzymes are globular proteins. This means that they are made up of

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What are Enzymes? Enzymes are globular proteins. This means that they are made up of: Carbon Hydrogen Nitrogen Which make up an amino acid. Amino acids join by peptide bonds (water is a by-product) forming dipeptides. Several dipeptides joined in a chain is called a polypeptide. More than one bonded polypeptide chains fold into a complex 3D shape, the sequence of amino acids determines the primary structure of the protein. Hydrogen bonding across this chain forms the proteins secondary structure. Further folding creates the tertiary structure of the globular protein this can be by hydrogen or disulphide bonding. The bonding of two or more polypeptide chains creates a protein with quaternary structure. The specific shape of globular proteins allows them to function as enzymes. As the enzyme has an active site which is specifically shaped to fit its substrate and form enzyme substrate complexes. What do Enzymes do? Enzymes are biological catalysts. This means that they are highly specific to a reaction and control the rate at which it occurs at in the cell. ...read more.


This is often described as the lock and key mechanism. As the enzyme acts as the lock and the substrate acts as the key. A newer theory is the Induced Fit Hypothesis. The enzymes active site is similarly shaped to fit the shape of the substrate, however when the substrate and the enzyme are close together and bind, the active site of the enzyme changes shape and becomes fully complimentary to the substrates shape. Enzymes are Sensitive... The rate at which an enzyme-controlled reaction will proceed at is effected by outside conditions. Enzymes work at an optimum temperature. At higher temperatures the molecules have greater kinetic energy so more collisions occur so the rate of reaction is higher. However at very high temperatures enzymes are denatured. This is when the tertiary structure of the enzyme (as it is a protein) is lost by hydrogen bonds being broken. So the enzyme looses its specific shape and therefore its active site. ...read more.


Enzyme controlled reactions can be prevented by inhibition. Competitive inhibitors prevent enzyme-substrate complexes forming. The inhibitor competes with the substrate to fit in the active site of the enzyme. So less enzyme-substrate complexes form and the rate of reaction is decreased. This can be overcome by increasing the amount / concentration of substrate. Non-competitive inhibitors act by binding to the enzyme at an area away from its active site, however the specific shape of the active site is changed. Therefore it is no longer specific to the substrate, so enzyme - substrate complexes do not form and the rate of reaction is decreased. Uses of Enzymes Enzymes are used in living organisms to control anabolic and catabolic reactions. E.g. Starch + Amalyase = 2Maltose Enzymes are used in food technology to avoid spoilage in processed foods. Enzymes that are acid tolerant are added to animal feed grains to make them more digestible. Diagnostic enzymes are used as biosensors, for example Clinistix to detect glucose in urine. Or, breathalyser to detect ethanol (alcohol). Ethanol and glucose act as substrates for enzymes on the biosensors. ...read more.

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