Chapter 8: Enzymes 8.4 and 8.5

Copyright Pearson Prentice Hall Energy in Reactions Activation Energy Chemists call the energy that is needed to get a reaction started the activation energy.

Copyright Pearson Prentice Hall Enzymes Some chemical reactions that make life possible are too slow or have high activation energies. These chemical reactions are made possible by catalysts.

Copyright Pearson Prentice Hall Enzymes Enzymes speed up chemical reactions that take place in cells.

Copyright Pearson Prentice Hall Enzyme Action The Enzyme-Substrate Complex Enzymes provide a site where reactants can be brought together to react, reducing the energy needed for the reaction. The reactants of enzyme-catalyzed reactions are known as substrates.

Enzymes work by forming enzyme-substrate complex - area known as active site - binding of substrate to active site forms enzyme-substrate complex - after binding to substrate, product is released and enzyme can be reused

Copyright Pearson Prentice Hall Enzyme Action An Enzyme-Catalyzed Reaction

Enzymes are specific (substrate specific to enzyme) - because of the binding at the active site, the substrate is very specific to the enzyme Most enzyme names end in -ase - sucrase is an enzyme that reacts with sucrose - enzyme names such as pepsin and trypsin give no clues as to their function

Copyright Pearson Prentice Hall Enzymes can be affected by any variable that influences a chemical reaction. – pH values – Changes in temperature – Enzyme or substrate concentrations Regulation of Enzyme Activity