1. Energy Chemical Reactions and Enzymes

2. Energy the ability to move or change matter found in many forms
can be converted from one form into another

3. Chemical Reactions
process that changes one set of chemicals into another
always involves changes in the chemical bonds that join the atoms in the compounds

4. Chemical Reactions H2CO3 H2O CO2 reactants
elements or compounds that enter into a chemical reaction 
products
elements or compounds produced by the chemical reaction
H2CO3
H2O
CO2 +
carbon dioxide plus water forms carbonic acid

5. Energy in Reactions
Some chemical reactions release energy and others absorb energy.
Energy changes are an important factor in determining whether a reaction will occur
C → A + B + Energy
A + B + Energy → C

6. Energy in Reactions Label each of the following reactions as either:
Energy-Releasing Reaction or
Energy-Absorbing Reaction
(from Holt Biology, pg. 39)

7. Energy in Reactions

8. Energy in Reactions

9. Energy in Reactions activation energy
energy needed to start a chemical reaction
ex: spark plug in an engine
Energy-Absorbing Reaction
Energy-Releasing Reaction
Products
Activation energy
Activation
energy
Reactants

10. Enzymes substances that increase the speed of chemical reactions
most enzymes are proteins
do not get used up in a chemical reaction

11. Enzymes work only within a certain set of conditions
enzymes are biological catalysts
catalysts
substances that reduce the activation energy of a chemical reaction

12. Enzymes & Activation Energy
Reaction pathway
without enzyme
Activation energy
Activation
energy
with enzyme
Reactants
Products

13. Enzyme Specificity
substrate – substance on which an enzyme acts during a chemical reaction
substrate = reactants
enzymes act only on specific substrates

14. Enzyme Specificity Example:
catalase – enzyme that breaks down hydrogen peroxide
Why is catalase written above the arrow and not included in the reaction?
hydrogen peroxide +
water
oxygen
catalase

15. Enzyme Specificity
active sites – the site on an enzyme that attaches to a substrate
enzymes are specific because only its substrate fits into its active site

16. Enzyme Characteristics
How Enzymes Work
McGraw - Hill
Hydrolysis of sucrose
McGraw - Hill