Plasma Membrane and Cell Boundary Quiz
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Questions and Answers

Why does a membrane containing unsaturated phospholipids stay fluid at lower temperatures?

  • The double bonds in unsaturated phospholipids increase rigidity.
  • Saturated phospholipids have more kinks that allow for easier movement.
  • The bent structure of the unsaturated fatty acid tails prevents tight packing. (correct)
  • Unsaturated phospholipids have more hydrogen bonds that increase fluidity.

    • How do fish adapt to cold environments with respect to their membrane fluidity?

  • By adjusting the proportion of unsaturated fatty acids in their membranes. (correct)
  • By changing the composition of cholesterol in their membranes.
  • By decreasing the proportion of unsaturated fatty acids in their membranes.
  • By increasing the proportion of saturated fatty acids in their membranes.

    • What role does cholesterol play in maintaining membrane fluidity?

  • Cholesterol expands the range of temperatures for optimal membrane function. (correct)
  • Cholesterol decreases membrane fluidity at all temperatures.
  • Cholesterol at low temperatures increases fluidity by tightening phospholipid packing.
  • Cholesterol at high temperatures reduces fluidity by encouraging tight phospholipid packing.

    • What observation led Larry Frye and Michael Edidin to conclude that membrane proteins move sideways within the plasma membrane?

    <p>The fusion of mouse and human cells.</p> Signup and view all the answers

    What effect does a decrease in temperature have on a membrane rich in saturated fatty acids?

    <p>It increases fluidity by promoting tighter phospholipid packing.</p> Signup and view all the answers

    What is the main function of the plasma membrane?

    <p>Maintaining an appropriate amount of molecules within the cell</p> Signup and view all the answers

    According to the fluid mosaic model, what surrounds the cell?

    <p>Proteins and lipids</p> Signup and view all the answers

    Why is the plasma membrane described as a fluid mosaic model?

    <p>Since it allows free lateral movement of proteins and other substances</p> Signup and view all the answers

    What feature do phospholipids in the plasma membrane have?

    <p>Two fatty acids attached to glycerol and a phosphate group</p> Signup and view all the answers

    How does the plasma membrane act as a selective barrier?

    <p>Regulating the flow of materials in and out of the cell</p> Signup and view all the answers

    Which of the following statements best describes the role of the plasma membrane?

    <p>It is a selective barrier that regulates the flow of materials into and out of the cell.</p> Signup and view all the answers

    What is the main structural component described in the fluid mosaic model of the plasma membrane?

    <p>Phospholipids</p> Signup and view all the answers

    How do proteins contribute to the fluidity of the plasma membrane according to the fluid mosaic model?

    <p>By being embedded in the lipid bilayer and allowing lateral movement.</p> Signup and view all the answers

    What is the significance of the phosphate group in a phospholipid molecule that makes up the plasma membrane?

    <p>It contributes to the fluidity of the membrane.</p> Signup and view all the answers

    Why is it important for the plasma membrane to be described as a semipermeable membrane?

    <p>To highlight its role in allowing selective passage of materials.</p> Signup and view all the answers

    What is the significance of the fatty acid tails of phospholipids in determining membrane fluidity?

    <p>Saturated fatty acids make the membrane dense and rigid at cooler temperatures.</p> Signup and view all the answers

    How does the presence of unsaturated fatty acids impact membrane fluidity at lower temperatures?

    <p>It prevents tight packing, maintaining fluidity when saturated fatty acids would solidify.</p> Signup and view all the answers

    What role does cholesterol play in maintaining membrane fluidity?

    <p>Cholesterol expands the range of temperatures for optimal membrane function.</p> Signup and view all the answers

    How do organisms like fish adapt to cold environments by changing their membrane composition?

    <p>By adjusting the ratio of saturated to unsaturated fatty acids.</p> Signup and view all the answers

    What experimental evidence supports the lateral movement of membrane proteins within the plasma membrane?

    <p>Fusing cells with labeled proteins demonstrated sideways movement.</p> Signup and view all the answers

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