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🧬AP Biology
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🧬AP Biology

FRQ 3 – Scientific Investigation (Short)
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Unit 1: Chemistry of Life
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Each FRQ type tests specific skills taught in particular units. Here's why certain units appear for each question type:

This mapping reflects College Board's exam structure - each FRQ type tests specific skills that are taught in particular units.

Practice FRQ 1 of 131/13

3. Phospholipids are the primary structural component of cell membranes. The fluidity of the membrane is critical for the function of membrane-bound proteins and the transport of molecules. Organisms such as bacteria can alter the chemical composition of their membrane lipids in response to changing environmental conditions to maintain homeostasis.

Scientists conducted an experiment to investigate how temperature affects the fatty acid composition of the plasma membrane in a specific strain of bacteria. They grew bacterial cultures in nutrient broth at three different temperatures: 10°C, 20°C, and 30°C. All other conditions, including pH, light intensity, and dissolved oxygen levels, were kept constant. After 48 hours, the scientists harvested the bacteria and analyzed the phospholipid tails to determine the percentage of unsaturated fatty acids in the cell membranes.

A.

Describe the difference in carbon-to-carbon bonding between a saturated fatty acid and an unsaturated fatty acid.

B.

Justify why the scientists maintained all conditions other than temperature—including pH, light intensity, and dissolved oxygen levels—as constants throughout the experiment.

C.

State the null hypothesis for the experiment regarding the effect of temperature on the composition of the plasma membrane.

D.

The scientists claim that the percentage of unsaturated fatty acids will be highest in the bacteria grown at 10°C. Based on the chemical properties of lipids, justify the scientists' claim.

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Free Response Question Practice

This practice environment simulates the AP AP Biology Free Response Questions section. Here are some guidelines:

  • Read each question carefully before responding. Pay attention to command verbs like "identify," "explain," "analyze," or "evaluate."
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Tip: Answer all parts of each question. Partial credit is often available, so even if you are unsure, provide what you know.