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AP®BiologyCollege BoardExam QuestionsUnit 4: Cell Communication & Cell CycleCell Communication

Cell Communication (College Board AP® Biology)

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Cell Communication

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Cell Communication

1
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Bobtail squid form a symbiotic relationship with the marine bacterium Vibrio fischeri, which helps the squid avoid predation through bioluminescence. The bacteria only produce light when their colony reaches a certain size through a process called quorum sensing. Which of the following best describes how V. fischeri coordinates this light-producing response?

  • Individual bacteria directly transfer DNA to each other through conjugation tubes.

  • Bacteria use local regulators which bind to receptors on nearby cells and stimulate specific signal transduction pathways.

  • The squid's light organ releases hormones that stimulate the bacteria to produce light.

  • Bacteria communicate through plasmodesmata to coordinate light production.

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2
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The pancreas contains specialized structures called islets of Langerhans that play a crucial role in glucose homeostasis. Figure 1 shows the changes in the blood of an individual after consumption of a meal. Which of the following best explains the relationship between blood glucose concentration and insulin concentration after the point that the meal is eaten?

Graph showing blood glucose and insulin concentrations over time after a meal. Solid line for glucose peaks, dashed line for insulin follows closely.
Figure 1. Graph showing how blood glucose and blood insulin concentrations change over time after consuming a meal.
Graph showing blood glucose and insulin levels over time. Solid line rises then falls post-meal; dashed line follows a similar pattern. Key included.

  • Blood glucose concentration increases as insulin production is increased.

  • High glucose stimulates the release of insulin from alpha cells in the islets of Langerhans.

  • High glucose stimulates the release of insulin from beta cells in the islets of Langerhans.

  • A negative feedback response is triggered by the increase of insulin in the blood.

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3
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During childbirth, the hormone oxytocin plays a vital role in stimulating uterine contractions. Which of the following best describes how oxytocin facilitates labor through positive feedback?

  • Oxytocin inhibits uterine contractions to prevent premature delivery

  • Stretch receptors inhibit oxytocin release as contractions increase

  • Oxytocin triggers contractions, which stimulate more oxytocin release, leading to stronger contractions

  • The process involves negative feedback to maintain constant contraction strength

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41 mark

Epinephrine is an important hormone that helps regulate glucose levels in the blood through the mechanism shown in Figure 2. A stable blood pH is important for maximising efficiency of this signal transduction pathway.

Diagram showing epinephrine binding to a cell membrane receptor, activating adenyl cyclase, converting ATP to cAMP, and promoting glycogen breakdown.
Figure 2. The second messenger model of cAMP being activated by the presence of epinephrine.

With reference to Figure 2, which option provides an accurate explanation for the effect of acidic pH on glucose levels?

  • H+ ions bind to epinephrine preventing it from binding to the receptor molecule and therefore increasing glucose levels in the blood.

  • Glucose levels rise as epinephrine binds more easily to membrane receptors, activating the second messenger model.

  • Membrane proteins become denatured therefore preventing the binding of epinephrine and reducing the blood glucose concentration.

  • Epinephrine binds to alternative protein molecules resulting in insulin release which leads to decreased blood glucose levels.

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5
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Epinephrine is a hormone which contributes to glucose regulation using the second messenger model. Which of the following options best explains the benefit of the model shown in Figure 3?

Diagram of epinephrine binding to cell membrane receptor, activating adenyl cyclase, converting ATP to cAMP, leading to protein kinase activation, affecting glycogen.
Figure 3. The second messenger model of cAMP being activated by the presence of epinephrine.

  • Each molecule of hormone (epinephrine) can produce many molecules of cAMP which in turn activate large numbers of enzymes.

  • The second messenger model provides a specific signal transduction pathway for the synthesis of glycogen from glucose in liver cells.

  • The second messenger model is controlled by positive feedback.

  • The signal transduction pathway produces one molecule of glucose per epinephrine molecule that binds to the receptor.

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