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2014 AP Biology Exam, question 1
Read each question carefully and completely. Write your response in the space provided for each
question. Only material written in the space provided will be scored. Answers must be written out in
paragraph form. Outlines, bulleted lists, or diagrams alone are not acceptable.
1. Catechol, a natural substance found in plants, reacts with oxygen to produce benzoquinone and water, as represented by the chemical equation above. The reaction is catalyzed in plants by the enzyme polyphenol oxidase. Accumulation of benzoquinone in plant tissue results in the gradual appearance of a brown color.
A student observes that lemon juice slows the browning of apple slices. The student claims that
lemon juice slows the browning process by altering the activity of polyphenol oxidase. To test the
claim, the student distributes equal amounts of a dilute catechol solution to 6 identical test tubes.
The pH of each solution was adjusted as shown in the table, and the initial absorbance was
recorded. Equal amounts of polyphenol oxidase were added to each reaction tube. After 10 minutes
at room temperature the absorbance of 389 nm light (A389) was measured for each sample.
Solutions containing greater concentrations of benzoquinone absorb more light. The changes in A389
are shown in the table below.
POLYPHENOL OXIDASE ACTIVITY
Test Tube pH Change in A389 After
Incubation with Enzyme
A 1.0 0.06
B 3.0 0.09
C 5.0 0.23
D 7.0 0.83
E 9.0 0.32
F 11.0 0.10
(a) On the axes provided, construct an appropriately labeled bar graph to analyze the effect of pH on polyphenol oxidase activity.
(b) Based on the experimental results, estimate the optimal pH of the enzyme. Explain your estimate by connecting the experimental results to the structure and function of proteins.
(c) Propose an appropriate control treatment for the experiment, and describe how the control treatment would increase the validity of the results.
Genetic engineering can be used to disrupt specific genes in the genome of an organism. Predict how
the browning of apple slices would be affected in a strain of apples that was genetically engineered to
lack functional copies of the gene encoding polyphenol oxidase. Justify your response.
PAGE FOR ANSWERING QUESTION 1
1. Cells transport substances across their membranes. Choose THREE of the following four types of cellular transport.
Osmosis Active Transport Facilitated diffusion Endocytosis/exocytosis
For each of the three transport types you choose
a. describe the transport process and explain how the organization of cell membranes functions in the movement of specific molecules across the membrane.
2. Membranes are important structural features of cells. Describe the role of membranes in the synthesis of ATP in either cellular respiration or photosynthesis.
2014 AP Exam, Question 7
According to the chemiosmotic model proposed by Peter Mitchell in 1961, an electrochemical gradient is linked to the synthesis of ATP in mitochondria. Construct an explanation of the chemiosmotic model by doing each of the following.
(d) Make a claim about the role of the inner mitochondrial membrane in ATP synthesis.
(e) Present ONE piece of evidence that supports the role you proposed in part (a).
(f) Provide reasoning to explain how the evidence you presented in part (b) supports the claim you made in part (a).