Factors Affecting Chemical Reactions: Temperature, Concentration, Pressure, Enzymes

1. Review with your table partner: What are four factors that increase the rate of a chemical reaction? (Fill your answers in on the next slide.) Burning is an example of a chemical reaction. • Why does kindling burn better than a large log? • Why is it harder to start a fire at a higher elevation? Why do these factors all have this effect on the rate of a chemical reaction? What do they have in common?

2. Chemical Reactions 4 factors that increase the rate of a non-enzyme catalyzed chemical reaction: • _______________of Reactants • _______________ of Reactants • _______________ • _______________

3. What do all of these factors have in common? They all increase the ______________ between the reactants. Higher temperature increases the _______________________________________________________________________

4. Review with your table partner: Discuss the terms inverse relationship and direct relationship (use resources if needed). Does the rate of a chemical reaction vary directly or inversely with the factors we discussed? What would the shape of each graph be (with rate of reaction on the vertical axis and the other factor on the horizontal axis?

5. Effect of temperature, concentration and pressure on the rate of a non-enzyme catalyzed reaction: ____________ relationship; ____________________________________________ Rate of Reaction Temperature or Concentration or Pressure

6. Activation Energy The amount of energy required to start a chemical reaction. Even reactions that give off energy may require a large amount of energy to begin. Example: The activation energy of paper burning is ___________________________

7. Discuss with your table partner: Which of the graphs below show a reaction that requires energy? Which of the graphs below show a reaction that releases energy? Be able to explain your answers. Why is there a higher level of energy during the transition phase?

8. Exothermic Reaction: A reaction that __________ energy. (Exo= _____) The graph below shows a exothermic reaction because the products have ________ energy than the reactants.

9. Endothermic reaction: A reaction that requires an ______________ of energy. (Endo= _____) The graph below shows a endothermic reaction because the products have ________ energy than the reactants.

10. Enzymes An enzyme is a protein that catalyzes a specific chemical reaction, by ____________________________________________ .

11. By lowering the activation energy, enzymes allow reactions to occur at body temperature that would otherwise require much higher temperatures. Example: The breakdown of sugar into carbon dioxide and water.

12. Enzymes The enzyme is not changed in the reaction and can catalyze the same reaction ________________. A substrate is a ___________ in an enzyme catalyzed reaction. (Example: starch is the substrate of the enzyme amylase) http://student.ccbcmd.edu/~gkaiser/biotutorials/proteins/enzsub.html

13. Active Site of an Enzyme The active site of an enzyme is the space that the substrate(s) bind to in order for the enzyme to catalyze the chemical reaction. Each enzyme catalyzes a ________chemical reaction.

14. Enzyme Shape The shape of the enzyme is critical for its function. If conditions cause an enzyme to lose its shape it will not be able to catalyze the reaction. The unfolding of an enzyme is called denaturation.

15. Discuss with your table partner: Below is a graph showing the typical effect of temperature on an enzyme-catalyzed reaction. With your table partner, describe the effect of temperature on the rate of enzyme activity and then try to determine why temperature has this effect. On the following slide, fill in the boxes with the reason why.

16. Key Concept Review

17. Effect of pH on Enzyme Activity If an enzyme becomes denatured due to changes in pH, it will not be able to catalyze the reaction, and the rate of reaction drops off sharply. Different enzymes have __________________ , which vary depending on the pH of their normal environment. Pepsin is found in the acidic stomach. Amylase is found in neutral conditions of the mouth Trypsin is found in alkaline conditions of the small intestine.

18. Applying the Concepts Some bacteria are extremophiles that can survive at very high temperatures, such as the hot springs in Yellowstone. Predict how their enzymes compare. ____________________________________________________________________________________________________________________________________________________________________________________

19. Discuss with your table partner: Study the graph comparing the rate of a reaction compared to the substrate concentration. Explain why there is initially an increased rate of reaction as the substrate concentration increases. Explain why the rate of reaction reaches a plateau for higher substrate concentrations.

20. Effect of substrate concentration on an enzyme –catalzyed reaction Initially, as the substrate concentration increases the reaction rate also increases due to __________________________________________________. However, this effect levels out when ____________ _________________________________________ .