1. Chemical Reactions Name 4 factors that increase the rate of a
non-enzyme catalyzed chemical reaction.
Temperature
Concentration of Reactants
Surface Area of Reactants
Pressure

2. What do all of these factors have in common?
They all increase the rate of collisions between the reactants.
Higher temperature increases the rate of collisions because the molecules are moving faster.

3. Chemical reaction animation:

4. Effect of temperature, concentration and pressure on the rate of a non-enzyme catalyzed reaction: Direct relationship; increased rate of reaction when increased.
Rate of Reaction
Temperature
or Concentration
or pressure

5. 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 451 degrees Fahrenheit

6. Exothermic Reaction: A reaction that gives off energy.
(Exo= out)
The graph below shows a exothermic reaction because the products have less energy than the reactants.

7. Endothermic reaction: A reaction that requires an overall input of energy. (Endo= In)
The graph below shows a endothermic reaction because the products have more energy than the reactants.

8. Enzymes
An enzyme is a protein that catalyzes a specific chemical reaction, by lowering the activation energy.

9. 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.

10. Enzymes
The enzyme is not changed in the reaction and can catalyze the same reaction repeatedly.
A substrate is a reactant in an enzyme catalyzed reaction. (Example: starch is the substrate of the enzyme amylase)

11. 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 specific chemical reaction.

12. Effect of substrate concentration on an enzyme –catalzyed reaction
Initially, as the substrate concentration increases the reaction rate also increases (due to increased collisions between the substrate and enzyme).
However, this effect levels out when all the enzymes’ active sites are full.

13. Effect of Temperature on an Enzyme-Catalyzed Reaction
Higher temperatures initially increases the rate of reaction.
However, higher temperatures can cause the enzyme to become denatured (unfold from its correct shape) and the rate of reaction drops sharply.

14. Key Concept Review
Rate of reaction drops if high temperature causes the enzyme to denature (lose its shape) and not be able to catalyze the reaction.
Initially, increased rate with increased temperature due to faster collisions between the substrate(s) and the enzyme .

15. 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 different optimal pH’s, 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.

16. 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.
Their enzymes
do not denature at
temperatures that
would denature
human enzymes,
and can therefore
catalyze reactions
in much hotter
conditions.