ENERGY & CHEMICAL REACTIONS I. Energy – is the ability to move or change matter - it is stored or released by chemical reactions - it exists in many forms; ex: light, heat, chemical energy, mechanical energy, and electrical energy

- energy powers the chemical reactions that occur in cells Chemical reactions are summarized by chemical equations, which are written in the following form: Reactants Products (starting material) (newly formed substances) ex: NaCl Na+ + Cl- H2O

II. Energy in Chemical Reactions In chemical reactions, energy is either absorbed or released as chemical bonds are broken or new ones are formed. Energy Releasing vs. Energy Absorbing Exergonic Endergonic

Activation Energy Energy is needed to start a chemical reaction. The energy needed to start a chemical reaction is called the activation energy. It is simply a chemical “push” that starts a chemical reaction.

Biochemical reactions – chemical reaction that occur in cells - they occur quickly and at relatively low temperatures because of the action of many enzymes enzymes – are substances that increase the speed of chemical reactions - most enzymes are proteins - they are catalysts, substances that reduce the activation energy of a chemical reaction

Enzymes Lower Activation Energy

III. Enzyme Specificity substrate – a substance on which an enzyme acts during a chemical reaction ex: 2H2O2 2H2O + O2 substrate starch glucose active site – a site on the enzyme that is specific for a certain catalase amylase

ENZYME Breaks Down Lipase Fats & oils Amylase Starch Maltase Maltose Protease Protein Catalase Hydrogen peroxide Carbohydrase Carbohydrates Lactase Lactose

Factors that affect enzyme activity: 1. temperature 2. pH level 3. enzyme & substrate concentration Enzyme-Substrate Complex