AP
®
Biology 2021 Scoring Commentary
Question 3
Note: Student samples are quoted verbatim and may contain spelling and grammatical errors.
Overview
This question described an experiment in which mammalian muscle cells were treated with resveratrol dissolved in
dimethyl sulfoxide (DMSO).
In part (a) students were asked to describe the advantage of aerobic respiration over fermentation in the mammalian
muscle cells. Responses were expected to demonstrate an understanding of the ATP yields of fermentation and
aerobic respiration (Learning Objective ENE-1.K in Topic 3.6).
In part (b) students were asked to identify an appropriate negative control. Responses were expected to demonstrate
proficiency in identifying experimental procedures (Science Practice 3.C).
In part (c) students were asked to predict the effect on short-term ATP production if resveratrol-treated cells are
grown in the absence of sugar. Responses were expected to demonstrate an understanding of the process of cellular
respiration (ENE-1.K in Topic 3.6).
In part (d) students were asked to justify the claim that, because resveratrol stimulates the production of the
components of the electron transport chain, treatment with resveratrol will increase oxygen consumption by the
cells. Responses were expected to demonstrate an understanding that oxygen acts as the terminal electron acceptor in
the electron transport chain in mitochondria (ENE-1.K.3 in Topic 3.6).
Sample: 3A
Score: 4
The response earned 1 point in part (a) for describing that aerobic respiration “can produce up to 36 ATP from a
single glucose molecule, while fermentation produces only two ATP.” The response earned 1 point in part (b) for
identifying that the negative control would be a “nutrient-rich solution without resveratol.” The response earned
1 point in part (c) for predicting that ATP production will “decrease.” The response earned 1 point in part (d) for
justifying that “oxygen acts as the final electron acceptor for the electron transport chain and will “require more
oxygen molecules to transfer electrons to.”
Sample: 3B
Score: 3
The response earned 1 point in part (a) for describing that aerobic respiration produces more ATP. The response
earned 1 point in part (b) for identifying the negative control would be to “use a muscle cell without resveratrol
added.” The response earned 1 point in part (c) for predicting that ATP production “would cease. The response did
not earn a point in part (d) for justifying that oxygen is “an electron transporter” rather than the final electron
acceptor in the increased transfer of electrons.
Sample: 3C
Score: 1
The response did not earn a point in part (a) because it does not describe that “more output” is more ATP. The
response did not earn a point in part (b) because it identifies the negative control as “to take away the mammalian
muscle cells that are enriched in glucose” rather than withholding resveratrol. The response earned 1 point in part (c)
for predicting the amount of ATP “will probably decrease.” The response did not earn a point in part (d) because it
does not justify that more electrons are transferred to oxygen as the final electron acceptor.
© 2021 College Board.
Visit College Board on the web: collegeboard.org.