2012 USABO Semifinal Exam Answers
1.
2.
3.
4.
5.
6.
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41.
D
E
B
B
C
A
D
C
D
E
E
A
C
B
D
B
B
E
C
E
D
C
B
E
C
A
C
E
D
B
E
D
A
E
A
D
D
B
D
C
D
42.
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55.
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81.
82.
C
A
C
A
A
A
C
E
D
B
A
E
C
B
E
B
C
D
D
C
D
A
A
B
A
D
E
C
A
E
D
ACDE
E
AE
AD
E
AC
AB
D
B
C
83. A
84. AC
85. C
86. B
87. A
88. B
89. A
90. A
91. A
92. C
93. D
94. B
95. C
96. ACD
97. B
98. C
99. B
100. ACD
101. A
102. D
103. A
104. CE
105. DE
106. C
107. C
108. B
109. E
110. D
111. E
112. D
113. A
114. D
115. A
116. B
117. B
118. B
119. E
120. D
PART C
Student Name____________________________ Student ID#___________________
Part C should be returned in its entirety with each student’s scantron. Place all
answers to Part C, Questions 1 and 2, on these two pages. Additional sheets of paper
may be used, if necessary. Be sure that each page has the Student’s Name and the
Student’s ID#. Please staple all pages together.
2012 USABO Semifinal Part C
1. The diagram shows an apparatus made by a student to investigate the effect of
temperature on the activity of ethanol fermentation of yeast. The conical flask
contains 2.5 g yeast suspended in 2% sucrose solution. The meniscus moves
down the glass tube (5 mL micropipette) during fermentation.
The data shown below were collected at regular time intervals to assess the amount of
suspension (mL) pushed in the glass tube due to CO2 accumulation
Time (min)
1
2
3
4
5
4oC
0
0
0.1
0.2
0.3
10oC
0.2
1.0
1.9
3.1
4.0
20oC
0.4
1.3
2.2
3.3
NO
RESULT
35oC
0.7
1.2
2.8
4.4
NO
RESULT
55oC
0
0.1
0.2
0.3
0.4
1
A. Estimate the average rate of CO2 production (mL CO2/min) for the yeast
suspension at 20oC using the values obtained in the period between 2 and
4 minutes.
1 ml/min
B. Estimate the specific rate of CO2 generation [millimoles CO2/(min∙g)] at
20oC.
0.017 – 0.018 mmoles CO2/min∙g
C. What would be the specific rate of ethanol accumulation [millimoles
CH3CH2OH/(min∙g)], if the fermentation reaction follows the equation
C6H12O6  2C2H5OH + 2CO2?
0.017 – 0.018 mmoles CH3OH /min∙g
Partial points should be given if the student identifies that the answer to B and C
will be the same, even if they don’t get the numbers right (or calculate any
numbers at all).
2. Complete the following table about hormones.
Hormone
Endocrine Gland
Chemical Class
Progesterone
Ovaries
Steroid
Thyroid-stimulating
Anterior pituitary
Glycoprotein
hormone
gland
Luteinizing hormone Anterior pituitary
Glycoprotein
Follicle-stimulating
hormone
Calcitonin
Prolactin
Antidiuretic
hormone
Anterior pituitary
gland
Thyroid gland
Anterior pituitary
gland
Posterior pituitary
gland
Glycoprotein
Peptide
Protein
Peptide
Regulated By
FSH and LH
Hypothalamic
hormones
Hypothalamic
hormones
Hypothalamic
hormones
Blood calcium level
Hypothalamic
hormones
Water/salt balance
We hope to see you as a Finalist!!
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