Practice Exam C
This is the third of six practice exams. These exam questions have been taken from
actual past BIS105 exams. The numbers in parentheses indicate the points for these
questions (out of 100 points for the whole exam). Thus these questions represented
approximately 1/6 the value of the exam. IF this is a reasonable estimate of the difficulty
of these questions, you should be able to answer them in 18/100 * 50 = 9 minutes
1. In a particular enzyme-catalyzed reaction, Vmax = 0.2 mol/sec and Km = 5 mM.
Assume the enzyme shows standard Michaelis-Menten kinetics.
a) (5) What is the rate of the reaction when [S] = 10 mM?
v = Vmax[S]/(Km + [S])
v = 0.2 x 10/(5 + 10) = 0.133
b) (5) Draw a Michaelis-Menten plot of the reaction kinetics, labeling the axes and
giving values for the two points where you know V.
mol/sec
0.2
0.133
0.1
0
5
10
2. The following data were obtained for an enzyme in the absence of an inhibitor and in
the presence of an inhibitor.
[S]
V(set 1)
V(set 2)
(mM)
(µmol/sec)
(µmol/sec)
1
8.6
24
2
16
40
4
28
58
10
42
70
(8) Draw a Lineweaver-Burke plot of the reaction kinetics, labeling the axes and giving
values for the two points where each line crosses the axes.
0.12
1/V
0
1/[S]
(mM)
1
0.5
0.25
0.1
1/[S]
1/V(set 1)
(µmol/sec)
0.12
0.062
0.036
0.024
1
1/V(set 2)
(µmol/sec)
0.042
0.025
0.017
0.014
1/v = Km/Vmax (1/[S]) + 1/Vmax
Using Excel (or other graphing program),
slope
Yint
xint
Km/Vmax
1/Vmax
-1/Km
0.108
0.010
0.097
0.032
0.010
0.309
Practice Exam D
This is the fourth of six practice exams. These exam questions have been taken from
actual past BIS105 exams. The numbers in parentheses indicate the points for these
questions (out of 100 points for the whole exam). Thus these questions represented
approximately 1/5 the value of the exam. IF this is a reasonable estimate of the difficulty
of these questions, you should be able to answer them in 20/100 * 50 = 10 minutes
1. The three structures below represent disaccharides.
gal- ß 1,4-glu
glu- α 1,2-fruc
lactose
sucrose
a) (4) Which of the three is a (are) reducing sugar(s)? Explain.
A: free pyranose 1 carbon
b) (3) Which of the three contain(s) glucose? Explain.
A, B, and C
c) (3) Which of the three contain(s) a ketose? Explain.
B: fructose is a ketose at the 2 carbon
glu- α 1,1-glu
trehalose
2. (5+5) The following enzymes catalyze reactions that have ΔG < 0. Diagram two of
the reactions, showing the chemical structures of primary substrates and products (but not
the coenzymes), and explain why the ΔG is negative.
a) glucokinase
glucose + ATP --> glucose-6-P + ADP
b) phosphofructokinase
fructose-6-P + ATP --> fructose-1,6-bisP + ADP
c) phosphoglycerate kinase
1,3-bisphosphoglycerate + ADP --> 3-phosphoglycerate + ATP
d) pyruvate kinase
PEP + ADP --> pyruvate + ATP
Diagrams of the reactions can be found in either textbook.
In every case, ΔG is negative from breaking less stable bonds and forming more stable
bonds