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Factors Affecting Enzyme Activity.

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Factors Affecting Enzyme Activity! Reactions proceed because the products have less energy than the substrates. However, most substrates require an input of energy to get the reaction going, (the reaction is not spontaneous). The energy required to initiate the reaction is called the activation energy. When the substrate(s) react, they need to form a complex called the transition state before the reaction actually occurs. This transition state has a higher energy level than either the substrates or the product. Outside the body, high temperatures often supply the energy required for a reaction. This clearly would be hazardous inside the body though! Fortunately we have enzymes that provide an alternative way with a different transition state and lower activation energy. The rate of the reaction without any external means of providing the activation energy continues at a much faster rate with an appropriate enzyme than without it. The maximum rate that any reaction can proceed at will depend, among other things, upon the number of enzyme molecules and therefore the number of active sits available. ...read more.


As the enzyme concentration increases, there are more active sites and the reaction can proceed at a faster rate. Eventually, increasing the enzyme concentration beyond a certain point has no effect because the substrate concentration becomes the limiting factor. 4. Substrate concentration: at a low substrate concentration there are many active sites that are not occupied. This means that the reaction rate is low. When more substrate molecules are added, more enzyme-substrate complexes can be formed. As there are more active sites, and the rate of reaction increases. Eventually, increasing the substrate concentration yet further will have no effect. The active sites will be saturated so no more enzyme-substrate complexes can be formed. Inhibitors Inhibitors slow down the rate of a reaction. Sometimes this is a necessary way of making sure that the reaction does not proceed too fast, at other times, it is undesirable. Reversible inhibitors: Competitive reversible inhibitors: these molecules have a similar structure to the actual substrate and so will bind temporarily with the active site. ...read more.


For example NAD, which transfers hydrogen away from one molecule in a dehydrogenase reaction and takes it to another molecule (see the Respiration QuickLearn). 2. Metal ions - most speed up the formation of the enzyme-substrate complex by altering the charge in the active site e.g. amylase requires chloride ions, catalase requires iron. Examples of the industrial uses of enzymes Perhaps the best known use is that of protease in biological washing powders. This enzyme helps to break down protein stains such as blood at lower washing machine temperatures. This means they save energy and are gentler on clothes. Some people are allergic to biological washing powders but this may be overcome by encapsulating the enzymes in wax from which they are only released during the wash. Another wide spread use of enzymes is that of pectinases in food modification. Pectin is a substance which, is found in cell walls and helps to hold the structure together. Pectinase is the name given to a group of enzymes which, break down pectins. They are therefore used to partially digest fruit and vegetables in baby food and to help extract fruit/vegetable juices. ...read more.

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