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Created with Fabric.js 1.4.5 Enzymes Enzymes are proteins, produced by organisms, that speed up chemical reactions. They are known as biological catalysts. How Enzymes Work Many chemical reactions take place in organisms. These reactions happen to slowly to keep organisms alive unless they are speeded up by enzymes. Most enzymes work inside cells and others work outside of cells Catalysts A catalyst speeds up a chemical reaction and remains unchanged at the end of the reaction. The 5 important properties of enzymes 1. They are all proteins. 2. Each enzyme catalyses one reaction. 3.They can be used again and again. 4.They are influenced by temperature. 5.They are influenced by pH. Effect of temperature on enzymes The activity of enzymes is influenced by temperature. The temperature at which the maximum rate of reaction occurs is called the optimum temperature. This is the best temperature for the enzyme. Enzymes and pH Enzymes are influenced by the pH of their surroundings. Many enzymes work best in neutral conditions, but some prefer acidic and some alkaline conditions. The shape of the active site can be altered by changes in pH. The bonds that hold the enzyme molecule in shape are broken by changes in pH. Enzymes and pH(cont.) When the rate of reaction is zero the shape of the active site has changed and the substrate mole- cules no longer fit. At these values of pH enzymes are denatured... Model Lock and Key Enzymes work on substances called substrates. The reaction takes place on a part of the surface of the enzyme called the active site. Only a substrate molecule with a shape that fits into the active site will take part in the reaction catalysed by this enzyme. Other substrates have the wrong shape to fit in and will not be involved in the reaction. This way of describing how enzymes work is known as the 'lock and key' model. The sustrate(the key)must have a shape that fits exactly into the active site(the key hole) of the enzyme(the lock).
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