2019 ap bio frq answers

3 min read 27-02-2025

2019 AP Biology Free Response Questions: Answers and Explanations

The 2019 AP Biology exam presented students with challenging free-response questions (FRQs) that tested their understanding of core biological concepts. This article provides answers and detailed explanations for each FRQ, helping you understand the reasoning behind the scoring and improve your preparation for future AP Biology exams. Remember that scoring rubrics can vary slightly from year to year, so this analysis focuses on the underlying biological principles.

Question 1: Enzyme Activity

This question focused on enzyme activity and its regulation. Students were presented with data on enzyme activity under different conditions and asked to analyze the results.

Part A: Describe the effect of temperature on enzyme activity. Explain the underlying mechanism responsible for this effect.

Answer: Increasing temperature initially increases enzyme activity due to increased kinetic energy leading to more frequent enzyme-substrate collisions. However, beyond an optimal temperature, activity decreases sharply because high temperatures denature the enzyme, altering its three-dimensional structure and active site, rendering it non-functional.

Part B: Predict the effect of a competitive inhibitor on the enzyme’s activity. Explain your prediction.

Answer: A competitive inhibitor would decrease the enzyme's activity. Competitive inhibitors bind to the enzyme's active site, competing with the substrate. This reduces the number of substrate molecules that can bind, thereby lowering the reaction rate. Increasing substrate concentration can overcome this inhibition.

Part C: Explain how allosteric regulation can affect enzyme activity.

Answer: Allosteric regulation involves the binding of a molecule (allosteric modulator) to a site other than the active site, causing a conformational change in the enzyme. This change can either increase (activation) or decrease (inhibition) enzyme activity. This is a non-competitive form of regulation.

Question 2: Cell Communication

This FRQ explored cell communication mechanisms, focusing on signal transduction pathways.

Part A: Describe the role of receptor proteins in cell communication.

Answer: Receptor proteins are transmembrane proteins that bind to specific signaling molecules (ligands), triggering a cascade of intracellular events. Different receptors bind to different ligands, allowing cells to respond specifically to particular signals in their environment.

Part B: Explain how a signal transduction pathway can amplify a signal.

Answer: Signal amplification occurs when a single ligand binding event leads to the activation of many downstream molecules. This often involves enzyme cascades, where each activated enzyme activates multiple molecules in the next step, resulting in a geometric increase in the signal.

Part C: Describe the role of second messengers in signal transduction.

Answer: Second messengers are small intracellular molecules (like cAMP or calcium ions) that relay signals from the cell surface to intracellular targets. They amplify the signal and often activate protein kinases, leading to changes in cellular activity.

Question 3: Photosynthesis and Cellular Respiration

This question tested the understanding of photosynthesis and cellular respiration and their interconnectedness.

Part A: Compare and contrast photosynthesis and cellular respiration in terms of energy transformation.

Answer: Photosynthesis converts light energy into chemical energy in the form of glucose. Cellular respiration breaks down glucose, releasing chemical energy in the form of ATP. Both processes involve redox reactions, but photosynthesis reduces CO2 to glucose, while respiration oxidizes glucose to CO2.

Part B: Explain the role of ATP in both processes.

Answer: In photosynthesis, ATP is produced during the light-dependent reactions and used to power the synthesis of glucose in the Calvin cycle. In cellular respiration, ATP is the primary energy currency, generated through oxidative phosphorylation and used to power various cellular processes.

Part C: Describe how the products of one process are the reactants of the other.

Answer: The products of photosynthesis (glucose and oxygen) are the reactants of cellular respiration. The products of cellular respiration (carbon dioxide and water) are the reactants of photosynthesis. This illustrates the cyclical nature of energy flow in ecosystems.

Question 4: Genetics and Evolution

(Note: The specifics of Question 4 will vary depending on the specific question presented in 2019.) This section generally focused on principles of inheritance, gene expression, and evolutionary mechanisms. The exact content will require referring to the original 2019 exam.

General Approach: To answer questions in this section, students should demonstrate understanding of Mendelian genetics, non-Mendelian inheritance patterns (e.g., incomplete dominance, codominance, multiple alleles), gene regulation (transcription and translation), mutations, natural selection, genetic drift, and speciation.

Question 5 and 6: Experimental Design and Data Analysis

These questions often involve analyzing experimental data and designing experiments to test hypotheses. The approach to answering these questions requires a solid understanding of experimental design principles, including control groups, independent and dependent variables, and statistical analysis.

This article provides a framework. To fully understand the answers and scoring, refer to the official 2019 AP Biology exam and scoring guidelines. Remember to practice with past FRQs to improve your understanding and exam-taking skills.