Worksheet 6
Enzymes
25 points
Name:
Section:
Date Turned in:
Introduction:
1. (2 pts) What role, if any, does the “active site” play in “enzyme specificity”?
2. (2 pts) Why do we need to reach enzyme saturation to measure the maximum
velocity?
Materials and Methods:
3. (2.5 pts) If a mixture of tyrosinase and L-DOPA was occurring at its Vmax, and
you added 3 more drops of substrate, do you think the overall reaction velocity
would increase, decrease, or stay the same? Assume the reaction has unlimited
substrate. Explain your reasoning.
4. (2.5 pts) If the L-DOPA happened to be colored and the dopachrome was clear,
could you measure the decrease in substrate concentration over time and get to a
similar reaction velocity? Why or why not?
5. (2 pts) If the L-DOPA was the same color as Dopachrome, how would that
change the methods of this experiment?
Results:
5. (5 pts) Using Prism, construct a substrate concentration v. reaction velocity
curve based on our class data. Draw one or two arrows showing the Vmax and Km
on the graph in their approximate locations! Make sure the axes are properly
labeled. Provide a descriptive figure legend that includes the quantitative values
for Vmax and Km!
note: contact your instructor if Prism has “ambiguous” on the results page
or you find a ~ symbol before the Vmax or Km
6. (2 pts) Which of the following Km values indicates the most efficient enzyme?
Explain your answer.
a. Km = 0.15 M
c. Km = 150 mM
5
b. Km = 1.5 x 10 nM
d. Km = 15 M
Discussion:
7. (2 pts) What effect did the inhibitor PTU (phenylthiourea) have on the reaction
velocity of tyrosinase? Explain WHY it had this effect.
8. (2 pts) Using your data and the concept of “structure is related to function”,
explain the velocity results as the temperature changed from very low to very high.
9a. (3 pts) Follow the link to the review article.
http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6976.2007.00094.x/pdf
Read the Introduction only.
The peptidoglycan cell wall is constructed, in part, by an enzyme called
transpeptidase. The antibiotic ampicillin is an inhibitor of transpeptidase. As you
will read, enzyme inhibition can lead to cell lysis.
a. What is cell lysis and why does it result in the inability of bacteria to
reproduce?
b. Why would inhibition only be effective “during cell growth”?
c. Why are human cells unaffected by this antibiotic?