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Catalysts and Catalysis

What are enzymes and what are they made of?


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October 25, 2008 3:29PM

Enzymes are biological catalysts. This means they break down substances without being changed themselves. This is why they can be used over and over again. Enzymes are made from amino acids joined together by different bonds, one of the type of bonds being hydrogen bonds. As enzymes have hydrogen bonds it means they are sensitive to pH and temperature. A temperature too low will mean that the molecules (substrate) which should fit to an area on the enzyme called the active site cannot do so as hydrogen bonds are stronger in colder conditions. (Enzymes change slightly as the substrate fits on to it) This would mean that the enzyme is less able to change shape slightly because the stronger hydrogen bonds make the enzyme less flexible. Temperatures which are too high for the enzyme (if they exceed the perfect temperature, called the optimum temperature, of the enzyme) denature the enzymes, meaning that they are unable to catalyse chemical reactions, this is due to the high temperature causing the hydrogen bonds which bond the amino acids together to beak, causing the enzymes active site to change shape, meaning that the substrate can no longer fit into the active site meaning that the rate of reaction of the chemical reaction is lower. There is a point when the hydrogen bonds, once broken, are no longer able to re-bond, meaning the enzyme could never "re-nature". This is very bad if the chemical reaction is necessary. If the pH which the enzyme is exposed to is not its optimum the rate of reaction will be slower as the pH changes the molecular shape of the enzyme, and can have an effect on the intermolecular forces of the Hydrogen bonds (it can weaken or strengthen them)