Chemical Reactions and Enzymes

Chemical Reactions A chemical reaction is a process that changes one set of chemicals into another. Causes chemical bonds to be rearranged. Example: 2H2 + O2  H2O Hydrogen gas and oxygen gas is changed into water. 2Na + Cl2 2NaCl Sodium and chlorine gas are changed into table salt

Parts of a Chemical Reaction Reactants: The elements or compounds that enter a chemical reaction. Found on the left side of the reaction arrow. 2H2 + O2  H2O 2Na + Cl2 2NaCl

Parts of a Chemical Reaction Products: The elements or compounds produced by a chemical reaction. Found on the right side of the reaction arrow 2H2 + O2  H2O 2Na + Cl2 2NaCl

Energy Changes Energy changes occur in every chemical reaction. Reactions that release energy occur spontaneously. Reactions that absorb energy require a source of energy to occur.

Energy-Absorbing Reaction The products have more energy than the reactants. Requires external energy to begin the reaction. Activation energy is the energy needed to start the reaction.

Energy-Releasing Reaction The reactants have more energy than the product. This reaction will happen on its own.

Catalysts A catalyst is a substance that speeds up the reaction rate without being changed during the process. Work by lowering the activation energy. Enzymes are proteins that act as biological catalysts.

Enzyme-Substrate Complex Enzymes act as a “clamp” that holds chemicals in the correct position to react faster. One of the reactants enters the protein enzyme and is held in place. The other reactant reacts with the chemical being held. The product is released.

Regulation of Enzyme Activity Enzymes are affected by pH and temperature. Changing the pH or the temperature can slow down or disable enzymes.