1. Bell Ringer #1
The human body maintains a temperature of around degrees at all times. Enzymes are involved in almost every chemical reaction in the body. Which of the following describes the connection between these two statements?
A. Enzymes function best at a specific temperature.
B. The body needs to be warm to prevent hypothermia.
C. The body is kept relatively warm to prevent too much enzyme action.
D. There is no connection between the two statements.

2. Bell Ringer #2
A student is investigating how reaction rate changes over a range of enzyme concentrations. The student uses excess reactants. Which of the following best represents the relationship between enzyme concentration and reaction rate? C. A. B. D.

3. Interactive Journal Entry “Enzymes SC.912.L.18.11”
Left Side
Right Side
Guided Notes (Note: when copying reduce size to 67% to fit in composition books; students can staple/tape it in landscape format)

4. Enzymes
SC.912.L Explain the role of enzymes as catalysts. Identify factors, such as pH and temperature, and their effect on enzyme activity.

5. Flow of energy through life
Life is built on chemical reactions

6. Nothing works without enzymes!
How important are enzymes?
all chemical reactions in living organisms require enzymes to work
building molecules
synthesis enzymes
breaking down molecules
digestive enzymes
enzymes are proteins
Review – What is the monomer of a protein? +
enzyme +
enzyme
We can’t live without enzymes!

7. How do Enzymes Work? Enzymes are Catalyst Speed up a chemical reaction
Lower the activation energy required for a chemical reaction to occur.

8. Enzymes aren’t used up Enzymes are not changed by the reaction
used only temporarily
re-used again for the same reaction with other molecules
very little enzyme needed to help in many reactions
product
substrate
enzyme
active site

9. It’s shape that matters!
Lock & Key model
shape of protein allows enzyme & substrate to fit
specific enzyme for each specific reaction

10. 1 2 3

11. Enzyme vocabulary Enzyme Substrate Products Active site
helper protein molecule
Catalyst
Substrate
molecule that enzymes work on
Products
what the enzyme helps produce from the reaction
Active site
part of enzyme that substrate molecule fits into

12. Factors Affecting Enzymes
Temperature pH
Enzyme concentration
Substrate concentration
Living with oxygen is dangerous. We rely on oxygen to power our cells, but oxygen is a reactive molecule that can cause serious problems if not carefully controlled. One of the dangers of oxygen is that it is easily converted into other reactive compounds. Inside our cells, electrons are continually shuttled from site to site by carrier molecules, such as carriers derived from riboflavin and niacin. If oxygen runs into one of these carrier molecules, the electron may be accidentally transferred to it. This converts oxygen into dangerous compounds such as superoxide radicals and hydrogen peroxide, which can attack the delicate sulfur atoms and metal ions in proteins. To make things even worse, free iron ions in the cell occasionally convert hydrogen peroxide into hydroxyl radicals. These deadly molecules attack and mutate DNA. Fortunately, cells make a variety of antioxidant enzymes to fight the dangerous side-effects of life with oxygen. Two important players are superoxide dismutase, which converts superoxide radicals into hydrogen peroxide, and catalase, which converts hydrogen peroxide into water and oxygen gas. The importance of these enzymes is demonstrated by their prevalence, ranging from about 0.1% of the protein in an E. coli cell to upwards of a quarter of the protein in susceptible cell types. These many catalase molecules patrol the cell, counteracting the steady production of hydrogen peroxide and keeping it at a safe level. Catalases are some of the most efficient enzymes found in cells. Each catalase molecule can decompose millions of hydrogen peroxide molecules every second. The cow catalase shown here and our own catalases use an iron ion to assist in this speedy reaction. The enzyme is composed of four identical subunits, each with its own active site buried deep inside. The iron ion, shown in green, is gripped at the center of a disk-shaped heme group. Catalases, since they must fight against reactive molecules, are also unusually stable enzymes. Notice how the four chains interweave, locking the entire complex into the proper shape.
catalase
SC.912.L Explain the role of enzymes as catalysts. Identify factors, such as pH and temperature, and their effect on enzyme activity.

13. Temperature Effect on rates of enzyme activity Optimum temperature
greatest number of collisions between enzyme & substrate
human enzymes
35°- 40°C (body temp = 37°C)
Raise temperature (boiling)
denature protein = unfold = lose shape
Lower temperature T°
molecules move slower
fewer collisions between enzyme & substrate

14. Temperature What is happening here? human enzymes reaction rate
37°
reaction rate
temperature

15. pH Effect on rates of enzyme activity
changes in pH changes protein shape
most human enzymes = pH 6-8
depends on where in body
pepsin (stomach) = pH 3
trypsin (small intestines) = pH 8

16. pH
What is happening here?

17. Enzyme concentration Effect on rates of enzyme activity
as  enzyme =  reaction rate
more enzymes = more frequently collide with substrate
reaction rate levels off
substrate becomes limiting factor
not all enzyme molecules can find substrate

18. What is happening here?
Enzyme concentration

19. Substrate concentration
Effect on rates of enzyme activity
as  substrate =  reaction rate
more substrate = more frequently collide with enzymes
reaction rate levels off
all enzymes have active site engaged
enzyme is saturated
maximum rate of reaction

20. Substrate concentration
What is happening here?

21. Bell Ringer #1 Re-Try
The human body maintains a temperature of around degrees at all times. Enzymes are involved in almost every chemical reaction in the body. Which of the following describes the connection between these two statements?
A. Enzymes function best at a specific temperature.
B. The body needs to be warm to prevent hypothermia.
C. The body is kept relatively warm to prevent too much enzyme action.
D. There is no connection between the two statements.

22. Bell Ringer #2
A student is investigating how reaction rate changes over a range of enzyme concentrations. The student uses excess reactants. Which of the following best represents the relationship between enzyme concentration and reaction rate? C. A. B. D.

23. We do:

24. You Do Questions
The following questions can be projected when an instructor reaches the “You Do” or an instructor can use the handout.

25. 1. The graph below shows how the activity of an enzyme changes over a range of pH values.
Which of the following conclusions can be drawn from this graph?
The optimum pH of the enzyme is 6.6.
The optimum pH of the enzyme is 5.8
The enzyme’s activity continually increases as pH increases from 5.0 to 9.0
The enzyme’s activity is greater around pH of 8.0 than around pH of 5.0.

26. 2. Many of the proteins in the human body are enzymes that catalyze chemical reactions. What is the relationship between enzymes and activation energy?
When an enzyme catalyzes a reaction, it increases the activation energy of the reaction
When an enzyme catalyzes a reaction, it increases the activation energy of the product.
When an enzyme catalyzes a reaction, it decreases the activation energy of the reaction.
When an enzyme catalyzes a reaction, it does not affect the activation energy of the reaction.

27. 3. Some bacteria live in hot springs
3. Some bacteria live in hot springs. Their cells contain enzymes that function best at temperatures of 70 °C or higher. At the temperature of 50 °C, how will the enzymes in these bacterial cells most likely be affected?
The enzymes will be destroyed by lysosomes.
The enzymes will lose their bond structure and fall apart.
The enzymes will require less energy to function than at 70 °C.
The enzymes will not increase the rate of reactions as much as they would at 70 °C.

28. 1. The graph below shows how the activity of an enzyme changes over a range of pH values.
Which of the following conclusions can be drawn from this graph?
The optimum pH of the enzyme is 6.6.
The optimum pH of the enzyme is 5.8
The enzyme’s activity continually increases as pH increases from 5.0 to 9.0
The enzyme’s activity is greater around pH of 8.0 than around pH of 5.0.

29. 2. Many of the proteins in the human body are enzymes that catalyze chemical reactions. What is the relationship between enzymes and activation energy?
When an enzyme catalyzes a reaction, it increases the activation energy of the reaction
When an enzyme catalyzes a reaction, it increases the activation energy of the product.
When an enzyme catalyzes a reaction, it decreases the activation energy of the reaction.
When an enzyme catalyzes a reaction, it does not affect the activation energy of the reaction.

30. 3. Some bacteria live in hot springs
3. Some bacteria live in hot springs. Their cells contain enzymes that function best at temperatures of 70 °C or higher. At the temperature of 50 °C, how will the enzymes in these bacterial cells most likely be affected?
The enzymes will be destroyed by lysosomes.
The enzymes will lose their bond structure and fall apart.
The enzymes will require less energy to function than at 70 °C.
The enzymes will not increase the rate of reactions as much as they would at 70 °C.