Chemical Reactions and Enzymes 2.4 Everything that happens in an organism is based on chemical reactions.

What is a chemical reaction? Process that changes one set of chemicals into another. Mass and energy are conserved during a reaction Law of Conservation of Matter-atoms cannot be created or destroyed

Parts of a reaction CO2 + H2O ------------- H2CO3 Reactants=what “enters” the chemical reaction Listed BEFORE the arrow Products=what is produced in the reaction Listed AFTER the arrow CO2 + H2O ------------- H2CO3

Energy in Reactions Release of energy—often occur on their own (seen as heat, light, sound) exothermic Absorption of energy---need a source of energy to occur endothermic Activation Energy---energy needed to get a reaction started

2.5 Enzymes Catalyst=substance that speeds up the rate of a chemical reaction by decreasing activation energy Enzyme=proteins that act as biological catalysts….they speed up the cell’s reaction lowers activation energy very specific: one enzyme works on one reaction

How Enzymes Work Provide a place where substrates (the reactants) are brought together to react (active site) The substrates and active site fit together like a key in a lock (called the enzyme- substrate complex) Stay together until the reaction is complete, then products are released

Enzymes… Work best at certain pH levels Have an optimum temperature Changing the best temperature or pH can cause the enzyme to be denatured- meaning the shape of the enzyme changes and it will no longer work.

Addition of the enzyme lowers the activation energy in the reaction

REMEMBER: enzymes are easiest to recognize by their names in a chemical equation. Generally they will end in -ASE!!