Enzymes

1. Enzymes

2. Review • Energy is the ability to do work. • There are several types of energy including kinetic and potential

3. Chemical reaction • Reactants- starting material for a chemical reaction • Products- newly formed substance

4. Exergonic Reactions • Products have less energy than reactants • Energy is given off • Spontaneous • Energy must still be provided to start process- activation energy • As the reaction takes place, the energy given off allows the reaction to continue

5. Activation Energy • Varies for different reactions • Determines the rate of the reaction -The higher the a.e., the more speed required to force the interaction, and the slower the reaction -The lower the a.e., the less speed required to force the interaction, and the faster the reaction

7. Endergonic Reactions • Products have more energy than reactants • Continuous input of energy is required- not the same as activation energy

9. Characteristics of Catalysts • Speed up spontaneous reactions • Do not change the end products • Do not get used up in the reaction • Speed up reactions by lowering the activation energy

10. Bonds • The weaker the bond, the more reactive the molecule is • The stronger the bond, the less likely a chemical reaction will break it = stable

11. Which is Better? • Biological processes such as building cells and digestion require chemical reactions so which would be better? • Weaker bonds break easily for reactions to occur • Strong bonds that are more stable, but also more controllable

12. Enzymes • Enzymes are biological catalysts • They allow spontaneous reactions to occur despite the fact that most of the bonds in Biology are too stable for reactions to occur at a usable rate

13. Kinetic Molecular Theory and Reactions • The KMT states that all molecules move randomly, colliding with each other • In order for a reaction to occur, molecules must collide hard enough to force their electron clouds to interact • Reactions CANNOT occur if molecules are not colliding • Energy must be provided -Exergonic= activation energy -Endergonic= continuous inputs of energy

14. Structures • Substrate- substance on which and enzyme acts during chemical reaction (H2O2) • Active site- groove in the enzyme that has a high affinity for the substrate

15. Substrate/Enzyme Relationship • The active site of the enzyme has a specific shape and distribution of electric charge • The substrate fits into that active site, coordinating in size, shape, and electric charge to the active site (Lock and Key) • Enzymes are very specific • Once the substrate has entered the active site, both substrate and enzyme begin to change shape (induced-fit)

16. Cont. • After both molecules have changed shape together, they continue to interact, bonds can be broken or new ones formed (reactions) as a result of this interaction • After the reaction has taken place, the enzyme reverts back to its original shape kicking the new product out • The enzyme is now ready to interact with new substrate • The reactions that take place during the interactions require less activation energy and thus allow the reactions to occur faster

17. 3 Steps of Enzyme Activity • Substrate enters active site • The enzyme changes shape so A.A. can interact with the substrate • A.A. interaction at active site puts stress on the bonds of the substrate making it easy to react (lowering A.E.)