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ENZYME STUDY GUIDE
Name _________________________
Period ____ DUE Date _________
Energy and Chemical Reactions
Use Ch. 2 Sec. 4 and Enzyme Notes to answer the following questions.
Matching: Answer the questions that follow by matching the correct phrase to the term.
_____
_____
_____
_____
_____
1.
2.
3.
4.
5.
substrate
metabolism
activation energy
energy
products
a.
b.
c.
d.
e.
ability to move or change matter
substance that an enzyme acts on
pushing a boulder
newly formed substances
all chemical reactions in an organism
Multiple Choice: Choose the correct answer for each of the following questions and write it in the margin to the
left of the question number.
6. Enzymes in your body probably work best at
a. 25 degrees Celsius
b. 30 degrees Celsius
c. 37 degrees Celsius
d. 98 degrees Celsius
7. The enzyme that breaks down hydrogen peroxide into water is
a. amylase
b. carbonic anhydrase
c. catalase
d. hydrogenase
8. Enzyme activity is affected by
a. temperature
b. any factor affecting the shape of the enzyme
c. pH
d. all of the above
9. A catalyst
a. provides extra energy for a reaction
b. lowers the activation energy of a reaction
c. eliminates the activation energy of a reaction
d. only allows irreversible reactions to occur
10. Without enzymes, the chemical reactions in your body would
a. happen too fast
b. occur at much the same rate as they do now
c. require a different pH
d. occur to slow to support life processes
11. What occurs when an enzyme and a substrate interact at an active site?
a. activation energy is reduced
b. the products are bound irreversibly
c. the enzyme is changed by the reaction
d. activation energy is increased
Short Answer: Read the passage below and answer the questions that follow. Ch. 2 Sec. 4 may help you.
Active Reading
During a chemical reaction, a substance on which an enzyme acts is called a substrate. Enzymes act
only on specific substrates. For example, the enzyme amylase assists in the breakdown of starch to glucose. In
this reaction, starch is amylase’s substrate.
An enzyme’s shape determines its activity. Typically, an enzyme is a large protein with one or more deep
folds on its surface. These folds form pockets called active sites. An enzyme’s substrate fits into an active site.
Step 1: When an enzyme first attaches to a substrate during a chemical reaction, the enzyme’s shape changes
slightly so that the substrate fits more tightly in the enzyme’s active site.
Step 2: At an active site, an enzyme and a substrate interact in a way that reduces the activation energy of the
reaction, making the substrate more likely to react.
Step 3: The reaction is complete when products have formed. The enzyme is now free to catalyze further
reactions.
12. Define the two key terms contained in this passage.
____________________________ ____________________________ 13. What substance is a substrate of amylase? ______________________
14. What determines an enzyme’s activity? _________________________ ______________________
15. For each Step, 1, 2, and 3, draw a picture representing what is going on at the molecular level. Label the
substrate, enzyme, active site, and products as appropriate for each picture. (use Fig. 15 p. 41 as a
reference)
Step 1:
Step 2:
Step 3:
Energy and Metabolism
Much of the human digestive process takes place in the stomach and small intestine. Glands secrete enzymes that break protein
chains by chemical reactions. Two important digestive enzymes are pepsin and trypsin. The effect of the pH on the activity of these enzymes
can be determined by analyzing the data below. Plot the data from the charts on the graph, then analyze the activity of the two enzymes to
answer the questions.
Use two different colors for your lines. You will need to title the data tables and your graph with appropriate, descriptive titles.
Label the x and y axes correctly, including units (pH does not have a unit). Spread your scale out to cover the entire graph. The pH scale
should go from 0 to 14 as whole numbers only. The percent scale should go from 0 to 100.
Table 1. ______________________________________________
pH
0.9
1.5
3.0
5.0
5.1
Activity of Pepsin (%)
0
65
100
20
0
Table 2. ______________________________________________
pH
4.0
5.0
6.5
7.5
9.0
Activity of Trypsin (%)
0
75
100
90
0
Graph 1. ____________________________________________________________________________
Analysis:
1. At which pH is pepsin most active? ___________
At which pH is trypsin most active? ___________
2. If pepsin and trypsin had to function together, which pH would produce the highest
activity? Explain.
3. What do you think would happen if you took an antacid prior to eating a hamburger?
4. The stomach is a highly acidic environment. Once food leaves the stomach, it enters
the small intestine, where it is neutralized by sodium bicarbonate. Where in the
digestive system do you think pepsin and trypsin are the most active? Explain.
5. What does the graph indicate about the relative acidity of the stomach and the small
intestine?