Section II of the AP Biology Exam contains six questions, consisting of two long free-response questions and four short free-response questions. You will have a total of 90 minutes to complete all questions. The directions will look something like this (read carefully!).
Directions: Questions 1 and 2 are long free-response questions that should require about 25 minutes each to answer and are worth 8–10 points each. Questions 3 through 6 are short free-response questions that should require about 10 minutes each to answer. Questions 3 through 6 are worth 4 points each.
Read each question carefully and completely. Write your response in the space provided following 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 unless specifically requested.
AP Biology Readers (the people who grade your free-response essays) expect students to interpret data and apply knowledge to new situations in the free-response questions. Some important things to keep in mind when writing your answers to the free-response questions are provided in the following list:
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Answer the question. Do not become distracted or waste time writing about tangential topics that you know more about than what is being asked. Focus your response.
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Think quantitatively. Use data whenever possible to explain your answer. This is especially necessary when the question features a graph, table, or other type of diagram (which many free-response questions now do).
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Be specific. Offer specific detailed examples where appropriate.
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Use vocabulary correctly and often. Hone your understanding of the words provided in the Key Terms lists in this book and the various biological ideas and situations to which they can be applied. This will help you use the correct terminology when writing your responses.
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Remember the Big Ideas. Know the four big ideas covered in the AP Biology course (this page), as they are reflected in many free-response questions. Understanding these ideas and being able to articulate them will help you craft your responses.
Okay, now it’s time for some practice. Take about 25 minutes and try to write a long free-response to the following question. This is an example of Long Question #2.
The regulation of the expression of gene products is crucial to the development of an embryo and the maintenance of homeostasis. The table below illustrates the mRNA levels, total protein levels, and total enzyme activity levels for three different enzymes. These enzymes are encoded by genes A, B, and C after being expressed in both the absence and presence of “Protein X” or “Protein Y.”
a. Describe differences in maintaining homeostasis in unicellular and multicellular organisms.
b. Construct a graph of the Total Enzyme Levels for each of the 3 genes. Be sure to show the results in the presence and absence of Protein X and Protein Y.
c. Analyze the data and describe the influence of Protein X and Protein Y on the gene expression of Enzyme A and Enzyme B. Include at which point in gene expression the regulation likely occurs.
d. Another scientist repeats the experiment with Protein Y and Enzyme C, and adds a known inhibitor to Protein Y to the tube. Predict the effect on mRNA, protein, and total enzyme levels as a result.
To help you grade this sample free response, we’ve put together a checklist that you can use to calculate the number of points that should be assigned to each part of this question. We’ll first explain the important points on the checklist and then give you sample student responses to show you how test reviewers would evaluate them.
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Describe differences in maintaining homeostasis in unicellular and multicellular organisms. (2pts total)
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Describe homeostasis in unicellular organisms
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Describe homeostasis in multicellular organisms
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Construct a graph of the Total Enzyme Levels for each of the 3 genes. Be sure to show the results in the presence and absence of Protein X and Protein Y. (4pts total)
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Proper data selection/data placement
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Proper axes
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Proper error bars
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Proper labels
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Analyze the data and describe the influence of Protein X and Protein Y on the gene expression of Enzyme A and Enzyme B. Include at which point in gene expression the regulation likely occurs. (2pts total)
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Expression of Enzyme A appears to be stimulated by Protein X and is unaffected by Protein Y. The mRNA, protein, and enzyme activity increased with Protein X, so the regulation must be pre-transcriptional.
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The expression of Enzyme B appears to be inhibited by Protein X (mRNA, protein, and enzyme activity reduced) so this seems like pre-transcriptional inhibition. The expression of Enzyme B appears to be stimulated by Protein Y. The mRNA and Protein Levels are the same, but the Enzyme Level is increased. This implies post-translational activation.
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Another scientist repeats the experiment with Protein Y and Enzyme C, and adds a known inhibitor to Protein Y to the tube. Predict the effect on mRNA, protein, and total enzyme levels as a result. (2pts total)
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The mRNA and protein levels would be unchanged. The Total Enzyme Activity Levels would likely increase to near 18,000.
The following response would earn full points.
a) Homeostasis is important in all living things. In unicellular things, temperature must be maintained and osmotic pressure must be controlled and pH must be regulated at a cellular level. These same things are important in multicellular things. In addition, a multicellular thing like a plant or an animal has to coordinate their cells to work together. Individual cells must have homeostasis, but the overall living thing must have it too. With more complex systems comes more things to regulate like blood pressure and heart rate.
b)
c) Gene A expression has no change with the addition of Protein Y, but it has increased transcription, protein, and enzyme activity with the addition of Protein X. It is likely that Protein X is an enhancer of transcription of gene A. Perhaps it binds directly to the promoter region of gene A and assists RNA polymerase to bind. It might also remove a repressor of transcription or work together with other transcription factors. The increase in mRNA would lead to increased protein and increased enzyme activity down the road.
Gene B has a decrease in mRNA, protein, and enzyme activity with Protein X. It has increased total activity with Protein Y. It is likely that Protein X is a repressor of transcription for gene B. It might bind to the promoter of gene B or to another transcription factor to prevent RNA polymerase binding or prevent transcription from occurring in another way. Since the enzyme activity increases with Protein Y, but the mRNA and the protein levels did not change, this means that the enzyme activity was somehow enhanced on the same amount of enzyme that was present without Protein Y. Protein Y might be an enzyme activator of Enzyme B. It might bind to Enzyme B directly or maybe the protein phosphorylates it or cleaves it to make the enzyme active.
d) It looks like Enzyme C is unaffected by Protein Y at the mRNA and protein levels, but it looks like the enzyme activity is turned off. With an inhibitor of Protein Y the enzyme level would likely return to the untreated level of arond 18,000. The mRNA and the protein would not change with the inhibitor of protein Y.
The most important advice for this section of the test is practice, practice, practice! No matter how well you think you know the material, it’s important to practice formulating your thoughts on paper.
You can also access free-response questions from recent exams on the College Board website at apstudent.collegeboard.org/apcourse/ap-biology/exam-practice.
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The free-response section features six questions, two of which require long responses. You will have 90 minutes to complete the entire section.
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Each question is worth a certain number of points. The long-response questions are worth 8–10 points, and the short-response questions are worth 4 points each.
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Your responses must be written in paragraph form; outlines are not acceptable. Diagrams can be used to supplement your writing but will not receive credit on their own (unless otherwise specified).
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Remember to keep your response focused and use specific data and examples (where applicable) to justify your answers.
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Familiarize yourself with the Key Terms in this book as well as the Big Ideas for the AP Biology course. Understanding these will help you write clear, focused, and accurate responses.
Respond to the following questions:
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Which topics from this chapter do you feel you have mastered?
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Which content topics from this chapter do you feel you need to study more before you can effectively compose a free response?
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Was there any content that you need to ask your teacher or another person about?
