AP Biology Scoring Guide

Unit 4 Progress Check: FRQ

1. Read each question carefully. Write your response in the space provided for each part of each question.
Answers must be written out in paragraph form. Outlines, bulleted lists, or diagrams alone are not
acceptable and will not be scored.

Growth hormone and insulin are protein hormones that regulate carbohydrate metabolism by
hepatocytes (liver cells) through the activation of intracellular signaling pathways. Researchers
investigated whether the two hormones trigger the same or different intracellular signaling pathways in
hepatocytes. The researchers added either growth hormone or insulin to parallel cultures of hepatocytes.
At several time points after the hormone addition, they purified total intracellular protein from the cells
and quantified the level of the phosphorylated forms of two proteins involved in two different signaling
pathways (Figure 1, and ).

Figure 1. The level of phosphorylated signaling proteins STAT5 (A) and protein kinase B (B) in cells
cultured in the presence of growth hormone or insulin

(a) Describe the first interaction that triggers signaling to begin in a target cell.

Please respond on separate paper, following directions from your teacher.

(b) Identify a dependent variable in the experimental design. Identify a negative control for the effects
of hormone addition. Identify a likely reason why the researchers continued their experiment for 240
minutes.

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 AP Biology Scoring Guide

Unit 4 Progress Check: FRQ

Please respond on separate paper, following directions from your teacher.

(c) Describe the hormone and signaling protein combination that produced the greatest and most
prolonged response. For the phosphorylated STAT5 response that reached 100 percent at 10 minutes in
Figure , calculate the rate of decrease (percent decrease per minute) in the detected level of
phosphorylated STAT5 from 10 to 30 minutes.

Please respond on separate paper, following directions from your teacher.

(d) The researchers claim that the similar regulation of carbohydrate metabolism by hepatocytes when
the cells are treated with growth hormone or insulin results from the activation of different signaling
pathways. Use the data from the researchers’ experiment to support their claim.

Please respond on separate paper, following directions from your teacher.

Part A

Select a point value to view scoring criteria, solutions, and/or examples and to score the response.

0 1

The response indicates that a ligand/chemical messenger, in this instance a hormone, binds to a receptor protein in a
target cell.

Part B (i)

Select a point value to view scoring criteria, solutions, and/or examples and to score the response

0 1

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 AP Biology Scoring Guide

Unit 4 Progress Check: FRQ

The response indicates that a dependent variable is the level of phosphorylated signaling protein OR the level of
phosphorylated STAT5 OR the level of phosphorylated protein kinase B.

Part B (ii)

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0 1

The response indicates that a negative control for the effects of hormone addition is the zero time point when
hormone is added or adding no hormone or a denatured hormone to an identical culture and taking samples at the
same time points

Part B (iii)

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0 1

The response indicates that the response to the hormone might take some time to start OR that the researchers
might have wanted to see how long a response to the hormone lasted.

Part C (i)

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0 1

The response indicates that addition of insulin caused a high level of phosphorylated protein kinase B (about 80

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beyond your school’s participation in the program is prohibited.
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 AP Biology Scoring Guide

Unit 4 Progress Check: FRQ

percent of maximum) right to the end of the experiment at 240 minutes.

Part C (ii)

Select a point value to view scoring criteria, solutions, and/or examples and to score the response.

0 1

The response indicates that the rate of decrease is between 3 and 3.5 percent per minute. .
per minute.

Part D

Select a point value to view scoring criteria, solutions, and/or examples and to score the response.

0 1

The response indicates that the data show that different signaling proteins are phosphorylated by the two different
hormones, which supports the researchers’ claim.

2. Read each question carefully. Write your response in the space provided for each part of each question.
Answers must be written out in paragraph form. Outlines, bulleted lists, or diagrams alone are not
acceptable and will not be scored.

Scientists used cells called fibroblasts to study factors that cause nondividing cells in the stage of
the cell cycle to reenter the cell cycle and undergo mitosis. In a laboratory, fibroblasts typically grow
and divide when they are cultured in a growth medium that contains 10% serum (the liquid part of
blood that remains after blood clots). If fibroblasts are cultured for 48 hours in the absence of serum
(serum-starvation), they stop dividing and enter the stage of the cell cycle.

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 AP Biology Scoring Guide

Unit 4 Progress Check: FRQ

The scientists divided serum-starved fibroblasts into groups to which they added no serum, 10% serum,
or 0.1% serum. Each of the groups with 0.1% serum was also treated to block the production of only
one or combinations of four proteins ( , , , and ) that are inhibitors of cyclin-dependent
kinases. The scientists grew the fibroblasts for 48 hours and then measured the amount of
replication taking place to determine whether the cells had reentered the cell cycle. The scientists
compared each group of cells to the group cultured with 10% serum and plotted the data (Figure 1).

Figure 1. replication by treated fibroblasts relative to replication by fibroblasts cultured

(a) Based on the data for the groups of cells cultured with 0.1% serum (groups 3 to 7), identify which
of the four proteins tested do(does) not appear to play a role in blocking cell cycle entry by fibroblasts.

Please respond on separate paper, following directions from your teacher.

(b) Based on the data for the groups of cells cultured with 0.1% serum (groups 3 to 7), identify the
groups(s) most likely to include cells undergoing mitosis.

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 AP Biology Scoring Guide

Unit 4 Progress Check: FRQ

Please respond on separate paper, following directions from your teacher.

(c) Neurons (nerve cells) of the central nervous system (brain and spinal cord) are in of the cell
cycle and generally do not divide in response to an injury. The scientists predict that they can use the
data from this experiment to help them treat individuals who suffer from spinal cord injuries. Provide
reasoning to support the scientists’ prediction.

Please respond on separate paper, following directions from your teacher.

(d) Interactions between cyclins and cyclin-dependent kinases control the cell cycle. Explain how the
presence or absence of inhibitors of cyclin-dependent kinases might play a role in normal cells
becoming cancer cells.

Please respond on separate paper, following directions from your teacher.

Part A

Select a point value to view scoring criteria, solutions, and/or examples and to score the response.

0 1

The response indicates that group 3 in which p16 is blocked does not appear to play a role in blocking cell cycle
entry.

Part B

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0 1

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 AP Biology Scoring Guide

Unit 4 Progress Check: FRQ

The response indicates that cells undergoing mitosis are most likely to be found in group 7 OR in groups 4, 5, 6,
and 7.

Part C

Select a point value to view scoring criteria, solutions, and/or examples and to score the response.

0 1

The response indicates that because blocking some of the cyclin-dependent kinase inhibitors in this experiment
made fibroblasts divide, the scientists might also successfully block different cyclin-dependent kinase inhibitors in
neurons of the spinal cord to make the neurons reenter the cell cycle and divide.

Part D

Select a point value to view scoring criteria, solutions, and/or examples and to score the response.

0 1

The response indicates that the lack of the appropriate cyclin-dependent kinase inhibitors might let cyclins and
cyclin-dependent kinases continue to form active complexes that will result in almost continuous cell cycling with
replication and cell division.

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participation in the program is prohibited.
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