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Do cells have one enzyme with lots of functions, or many enzymes, each with just one function? Enzymes. Magical proteins necessary for life. So how do enzymes work? How do they catalyze just one specific biochemical reaction? In a puzzle, only two pieces will fit together properly. Understanding that is one of the main steps in understanding how enzymes work. Enzyme FunctionHow do enzymes speed up biochemical reactions so dramatically? Like all catalysts, enzymes work by lowering the activation energy of chemical reactions. Activation energy is the energy needed to start a chemical reaction. This is illustrated in Figure below. The biochemical reaction shown in the figure requires about three times as much activation energy without the enzyme as it does with the enzyme. An animation of how enzymes work can be seen at http://www.youtube.com/watch?v=CZD5xsOKres (2:02).
The reaction represented by this graph is a combustion reaction involving the reactants glucose (C6H12O6) and oxygen (O2). The products of the reaction are carbon dioxide (CO2) and water (H2O). Energy is also released during the reaction. The enzyme speeds up the reaction by lowering the activation energy needed for the reaction to start. Compare the activation energy with and without the enzyme. Enzymes generally lower activation energy by reducing the energy needed for reactants to come together and react. For example:
The active site is specific for the reactants of the biochemical reaction the enzyme catalyzes. Similar to puzzle pieces fitting together, the active site can only bind certain substrates. This enzyme molecule binds reactant molecules—called substrate—at its active site, forming an enzyme-substrate complex. This brings the reactants together and positions them correctly so the reaction can occur. After the reaction, the products are released from the enzyme’s active site. This frees up the enzyme so it can catalyze additional reactions. The activities of enzymes also depend on the temperature, ionic conditions, and the pH of the surroundings. Some enzymes work best at acidic pHs, while others work best in neutral environments.
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This page titled 1.18: Enzyme Function is shared under a CK-12 license and was authored, remixed, and/or curated by CK-12 Foundation via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. What speeds up reactions by lowering the activation energy?The answer is enzymes. Enzymes in our bodies are catalysts that speed up reactions by helping to lower the activation energy needed to start a reaction. Each enzyme molecule has a special place called the active site where another molecule, called the substrate, fits.
How does an enzyme lower the activation energy of a reaction?Enzymes generally lower activation energy by reducing the energy needed for reactants to come together and react. For example: Enzymes bring reactants together so they don't have to expend energy moving about until they collide at random.
How does an enzyme increase the speed of a reaction?Enzymes are biological catalysts. Catalysts lower the activation energy for reactions. The lower the activation energy for a reaction, the faster the rate. Thus enzymes speed up reactions by lowering activation energy.
When an enzyme decreases the activation energy of a reaction quizlet?Enzymes lower the energy of activation by forming an enzyme-substrate complex allowing products of the enzyme reaction to be formed and released. Enzyme catalysed reactions occur at a particular place on the surface of the large enzyme molecule called the active site (as in heterogeneous catalysts).
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