1. Daily Quiz
One of the papers that you picked up on the way in is a 1st Nine Weeks Assessment Study Guide.
Get out a blank sheet of paper and begin working on it.
In addition, get out the two pieces of paper from last class (Enzyme D1 Notes and Toothpickase Lab Sheet).

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

3. Enzymes
Objective: Analyze the role of enzymes in organisms and Interpret a graph of the effect of an enzyme on the activation energy in a chemical reaction.
Essential Question: Why are the actions of an enzymes important to us?

4. The things you need to write will be underlined and will be blue.

5. Flow of Energy in Life Life is built on chemical reactions.
Transforming energy from one form to another.
sun

6. Chemical Reactions of Life
These chemical reactions are the processes of life…
BUILDING MOLECULES
SYNTHESIS
BREAKING DOWN MOLECULES
DIGESTION

7. Activation energy
Breaking down large molecules requires an initial input of energy.
Activation Energy
Large Biomolecules are Stable
Must Absorb Energy to Break Bonds
Need a spark to start a fire
energy
cellulose
CO2 + H2O + heat

8. Activation Energy
Activation Energy: the energy required for a reaction to begin.
Like the energy needed to push a ball up a hill; once at the top, the ball will roll down the other side of the hill on its own.

9. Reducing Activation energy
Catalysts
Reduce the amount of energy to start a reaction.
Lower the activation energy.
Make it easier for reactions to start.
Allow the reaction to happen faster.
Why?
reactant
product
uncatalyzed reaction
catalyzed reaction
NEW activation energy

10. What are enzymes? Enzymes are proteins that act as a Catalyst
They work by…
Lowering the activation energy required for a chemical reaction to occur
Speeding up a chemical reaction
Increase the reaction rate
They are needed for almost all processes of life to occur
Digestion, building proteins, the immune system…

11. Enzymes as Catalyst

12. 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
enzyme
substrate
product
active site

13. What else do you notice about their names?
Enzymes are proteins
Each enzyme is the specific helper to a specific reaction
each enzyme needs to be the right shape for the job
enzymes are named for the reaction they help
sucrase breaks down sucrose
proteases breakdown proteins
lipases breakdown lipids
DNA polymerase builds DNA
What else do you notice about their names?

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

15. Enzymes aren’t used up
When enzymes are used in a chemical reaction they 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
enzyme
substrate
product
active site

16. How do enzymes work? If conditions change, enzymes could denature
Enzymes often only work within a narrow range of conditions
Since enzymes are proteins, they depend on being the correct shape to function
If conditions change, enzymes could denature
Denature = unfold or change the shape of the enzyme
enzyme
enzyme
Change in conditions
enzyme

17. 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.
SC.912.L Explain the role of enzymes as catalysts. Identify factors, such as pH and temperature, and their effect on enzyme activity.

18. Temperature
Enzymes work best at a specific temperature: Optimum temperature
greatest number of collisions between enzyme & substrate
human enzymes
35°- 40°C (body temp = 37°C)
Raising temperature (boiling) can cause the protein to denature protein
unfold = lose shape
Change the shape = change the function
Lowering the temperature cause the molecules to move slower
fewer collisions between enzyme & substrate
It still works but at a much slower rate

19. Girl, your so hot you denature my proteins

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

21. pH Enzymes work best at a specific pH range: Optimum pH
Changes in pH can cause enzymes to denature
If you change the shape, you change the function.
most human enzymes = pH 6-8
depends on location in body
pepsin (stomach) = pH 3
trypsin (small intestines) = pH 8

22. pH
What is happening here?

24. Enzyme concentration E E E E E E E E E
The more enzymes that are present = more reactions can take place.
As the number of enzymes  = The reaction rate will 
more enzymes = more collisions with substrate
reaction rate levels off
substrate becomes limiting factor
not all enzyme molecules can find substrate E E E E E E E E E

25. Enzyme concentration
What is happening here?

26. Substrate concentration
As the number of substrate increase = the reaction rate will increase
more substrate = more frequent collisions with enzymes
reaction rate levels off
all enzymes have active site engaged
enzyme is saturated
maximum rate of reaction

27. Substrate concentration
What is happening here?

29. Work Period
When we did Toothpickase, we were looking at how various factors affected enzyme activity.
Now, let’s graph our results and compare it to the notes we took today.

30. The human body maintains a temperature of around 98
The human body maintains a temperature of around 98.6 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.

31. 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.

32. Which of the following conclusions can be drawn from this graph?
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. A

33. 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. C

34. The enzymes will be destroyed by lysosomes.
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. D

35. 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.

36. 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.

37. 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.