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Enzyme structure and function

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Enzyme structure and function * Introduction * What is an enzyme? * What does it do? Catalyses reactions * What it is made of? - Enzymes are Proteins > Amino acids > Polypeptide bonds/structure * (Primary/Secondary/Tertiary) * Enzymes and their specific substrates * Active sites > Lock and key theory/Induction Fit > Inhibition * Other factors, which affect rate of reaction (Temperature and pH) > thermostable enzymes found within thermophilic bacteria * Uses of enzymes (Biological/Commercial uses) * Enzyme immobilisation * Conclusion Enzyme Structure and Function Enzymes are biological catalysts. A catalyst being a molecule, which helps speed up the rate, of which a reaction occurs. Just like iron acts as a catalyst during the Haber process, an enzyme speeds up a biological reaction. They are extremely important as an enzyme catalyses virtually every reaction that occurs in the metabolism of an organism. It is important to note that after a reaction, the actual enzyme remains unchanged; with only the substrate changing into the product. Enzymes are globular proteins, which means that their structure is made up of polypeptide chains, each made up of amino acids, which are joined together by peptide bonds (condensation and hydrolysis). Globular is its quaternary structure feature, and unlike fibrous proteins, globular proteins are spherical and highly soluble. ...read more.


This can be resolved by increasing the concentration of the substrate. Competitive inhibitors can be permanent or temporary. Non-Competitive Inhibitors These do not compete for the enzyme active site, instead the attach themselves to another part of the enzyme. By doing so, they disrupt the overall shape of the enzyme causing the active site to deform, and unable to accept any substrates. Non -competitive inhibitors can be irreversible, however Allosteric inhibitors are temporary non-competitive inhibitors. Enzyme inhibition is usually part of the normal biological metabolism to control the rate at which an enzyme works. This works by feedback from a final product, which acts as an inhibitor to the enzyme, which produced it - this is called 'end product inhibition', as the diagram will explain. Sometimes, inhibition occurs when external chemicals enter the body and interferes with the enzyme action. Things like poisons and drugs (alcohol) can seriously affect enzymes - with deadly results. The poison cyanide is an inhibitor, which targets the enzyme cytochrome oxidase, this is responsible for respiration, and so, the body dies from the lack of ATP. To act as a catalyst, the enzyme actually reduces the activation energy required to cause a reaction to happen. Giving the reactant molecules more kinetic energy can further increase this reaction - heating the substances causes the molecules to vibrate faster, thus increasing the chances of colliding with another. ...read more.


Enzymes are highly efficient biological catalysts made up of protein. They are specific towards the substrate that they catalyse, this is done either via the "lock and key" theory, or the "Induced fit hypothesis" The efficiency of enzymes can be described by the turnover over number, which is how much substrate molecules is turned into product in one minute by one molecule of enzyme. The table below summarises some specific turnover rates for some enzymes: Enzyme Turnover Number Carbonic Anhydrase 36,000,000 Catalase 5,600,000 Chymotrypsin 6,000 Lysozyme 60 Enzymes, and their role in biological organisms are affected by their environmental temperature and pH levels. During these extremes, the efficiency of the enzyme is compromised as the enzyme denatures - changing the shape of the active site. Enzymes can also be inhibited - irreversible inhibitors render enzymes permanently inactive and include several very toxic substances such as the cyanide ion and heavy metal ions. Reversible inhibitors can be competitive and non-competitive and play crucial role in regulating enzyme activity. Enzymes also play an important role in industry applications such as food and medicine. For example, an enzyme called acetylcholinestrase is used for operations involving nerves and in the production of something we all know about - alcohol. Rennin is another enzyme involved in the production of cheese, and when things get messy, Protease (protein digesting enzyme) is there in the form of washing up powder to clean things up. ...read more.

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