2021 AP Exam Administration Sample Student Responses - AP Biology: Free-Response Question 3

2021

AP

®

Biology

Sample Student Responses

and Scoring Commentary

Inside:

Free Response Question 3

•• Scoring Guideline

•• Student Samples

•• Scoring Commentary

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AP® Biology 2021 Scoring Guidelines

Question 3: Scientific Investigation 4 points

Researchers hypothesize that the plant compound resveratrol improves mitochondrial function. To test this

hypothesis, researchers dissolve resveratrol in dimethyl sulfoxide (DMSO). The solution readily passes through

cell membranes. They add the resveratrol solution to mammalian muscle cells growing in a nutrient-rich

solution (culture medium) that contains glucose. They measure ATP production at several time points after the

addition of the resveratrol solution and find an increase in ATP production by the muscle cells.

(a)

Describe the primary advantage for a mammalian muscle cell in using aerobic respiration

over fermentation.

• More ATP (per gluco

se molecule) is produced by aerobic respiration.

1 point

(b)

Identify an appropriate negative control for this experiment that would allow the

researchers to conclude that ATP is produced in response to the resveratrol treatment.

Accept one of the following:

• The researchers must run the experiment without adding resveratrol.

• The researchers must treat the cells with DMSO alone.

1 point

(c)

Predict the effect on short-term ATP production when resveratrol-treated mammalian

muscle cells are grown in a culture medium that lacks glucose or other sugars.

Accept one of the following:

• No ATP production

• Reduced ATP production

1 po

int

(d)

The researchers find that resveratrol stimulates the production of components of the

elect

ron transport chain. The researchers claim that treatment with resveratrol will also

increase oxygen consumption by the cells if glucose is not limiting. Justify the claim.

• More electrons can be transferred so that more oxygen is required as the final electron

accept

or.

1 point

Total for question 3 4 points

Q3 Sample A 1 of 1

Q3 Sample B 1 of 1

Q3 Sample C 1 of 1

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.

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