AP®BiologyCollege BoardExam QuestionsUnit 3: Cellular EnergeticsCellular Energy & Fitness

Cellular Energy & Fitness (College Board AP® Biology)

Exam Questions

5 mins5 questions
1
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The laws of thermodynamics are fundamental principles that govern the transfer of energy, including energy within living systems. A scientist is studying energy flow in an aquatic ecosystem. Which of the following best applies the second law of thermodynamics to this biological system?

  • Living organisms in the ecosystem are always transferring energy to their surroundings, increasing the overall entropy of the universe.

  • Energy within the ecosystem cannot be created or destroyed.

  • The total energy of the ecosystem remains constant, even if converted between forms.

  • Living organisms in the ecosystem need energy to fuel metabolism, meaning that they decrease the entropy of the universe.

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2
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All organisms require a constant input of energy. Cells obtain energy through chemical means, such as feeding or photosynthesis. Which of the following best explains why organisms need a constant input of energy?

  • To allow transfer of energy to the environment.

  • To create energy during metabolic reactions.

  • To maintain order, and power chemical processes inside cells.

  • To enable cells to decouple energy-requiring processes from energy-releasing processes.

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3
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Every metabolic process inside cells involves a change in free energy, known as incrementG (delta G), e.g. for the formation of sucrose from glucose and fructose incrementG = +27, while for the breakdown of ATP into ADP and Pi incrementG = -30. Which of the following reactions might be coupled together within a cell?

  • incrementG = +15 and incrementG = +25

  • incrementG = -15 and incrementG = -25

  • incrementG = -15 and incrementG = -5

  • incrementG = -25 and = incrementG +22

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4
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Hemoglobin in red blood cells binds to oxygen in the lungs and transports it to tissues for aerobic respiration. Hemoglobin comes in different forms, e.g. hemoglobin F, hemoglobin S and hemoglobin A. Which of the following best explains why different types of hemoglobin can be found in living organisms?

  • All types of hemoglobin can bind to oxygen most effectively at the oxygen concentrations present in the lungs.

  • Haemoglobin variant HbS causes sickle-cell disease, in which red blood cells take on a different shape.

  • Hemoglobin variation means that blood can carry oxygen effectively in a range of environmental conditions.

  • Hemoglobins are soluble in the blood plasma, allowing oxygen to be transported efficiently.

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5
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Research has shown that cells grown at 22 °C and at 32 °C differ in their membrane composition. Membranes of cells grown at 32 °C have been shown to contain phospholipids with fewer unsaturated fatty acids and more saturated fatty acids than those of cells of the same type grown at 22 °C. Which of the following is a valid claim that can be made from this observation?

  • Cells that have membranes with higher saturated fatty acid content have a survival advantage.

  • Cells that have membranes with higher unsaturated fatty acid content have a survival advantage.

  • The fatty acid composition of cell membranes can change in response to environmental stimuli.

  • Increasing the temperature causes unsaturated fatty acids to become saturated.

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