1. Energy and Chemical Reactions Biology Chapter 2, Section 4 Dr. Steve W. Altstiel Naples American High School

2. Objectives Evaluate the importance of energy to living things. Relate energy and chemical reactions. Describe the role of enzymes in chemical reactions. Identify the effect of enzymes on food molecules.

3. Energy for Life Processes Energy – the ability to move or change matter. Exists in many forms: –Light energy –Heat –Chemical energy –Mechanical energy –Electrical energy Energy can be stored or released in a chemical reaction.

4. Energy for Life Processes Cont… Chemical Reaction – process during which chemical bonds between atoms are broken and new ones are formed, producing new substance(s). Reactants  Products NaCl  Na + + Cl -

5. Energy in Chemical Reactions Chemical reactions either absorb or release energy when chemical bonds are formed or broken. Metabolism – all the chemical reactions that occur within an organism.

6. Activation Energy Activation energy is the amount of energy needed to start a chemical reaction. –Flame lighting a log. –Spark from spark plug causing gasoline to light.

7. Enzymes Enzymes are substances that increase the speed of a chemical reaction by reducing the activation energy. –Catalyst – enzymes that lower activation energy

8. Enzyme Specificity Substrate – a substance on which an enzyme acts during a chemical reaction. (Page 41) Active Site – deep folds in a large protein (enzyme) which form pockets. –Enzymes work only on a specific substrate, because that particular substrate is the only substance that fits into the active site.

9. Steps of Enzyme Action 1.Substrate attaches to enzyme. Enzyme slightly changes shape for substrate to fit tightly into active site. 2.At the active site, enzyme and substrate interact lowering the activation energy of the reaction, thus causing the substrate to more likely react. 3.Once the products have formed, the reaction is complete. The enzyme can be used again.