Chapter 5: The Plasma Membrane Functions Quiz
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Questions and Answers

What is the main function of the plasma membrane?

  • Enclosing the cell and defining its boundaries (correct)
  • Maintaining the characteristic differences between organelles and cytosol
  • Creating a barrier that is permeable to most water-soluble molecules
  • Determining the size and shape of the cell

    • What is the common general structure of biological membranes?

  • A continuous single layer of lipid molecules
  • A thin film of lipid and protein molecules held together mainly by non-covalent interactions (correct)
  • A rigid and non-dynamic structure with fixed molecules
  • A double layer of lipid and protein molecules held together by covalent interactions

    • What distinguishes the functions of cytomembranes in eukaryotic cells?

  • They determine the size and shape of the cell
  • They are impermeable to most water-soluble molecules
  • They maintain the characteristic differences between the contents of each organelle and the cytosol (correct)
  • They enclose the cell and define its boundaries

    • What is a key characteristic of cell membranes?

    <p>They are dynamic, fluid structures, with most molecules able to move about in the plane of the membrane</p> Signup and view all the answers

    Which type of molecules do lipid layers serve as a barrier to?

    <p>Most water-soluble molecules</p> Signup and view all the answers

    What is a function of biological membranes?

    <p>Maintaining essential differences between the cytosol and the extracellular environment</p> Signup and view all the answers

    What is the function of protein molecules that span the lipid bilayer in the membrane?

    <p>Transporting specific molecules across the membrane</p> Signup and view all the answers

    What is the mean thickness of the plasma membrane as defined by the electron microscope (EM)?

    <p>8.5nm</p> Signup and view all the answers

    What covers the outer side of the plasma membrane in animal eukaryotic cells?

    <p>Cell-coat or glycocalyx</p> Signup and view all the answers

    What is the chemical composition of a plasma membrane isolated and purified from red blood cells (RBC)?

    <p>42% proteins, 50% lipids, 8% carbohydrates</p> Signup and view all the answers

    What are the main components of the membrane lipids found in the plasma membrane?

    <p>Phospholipids, sterols, and glycolipids</p> Signup and view all the answers

    Which molecule forms the framework (bilayer) of the membrane and is the most numerous of the membrane lipids?

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

    What are the main phospholipids observed in the plasma membrane of mammals?

    <p>Phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, sphingomyelin</p> Signup and view all the answers

    In terms of chemical composition, how do cytomembranes differ from plasma membranes?

    <p>Contain more protein, less lipids, and no cell-coat</p> Signup and view all the answers

    What are amphiphilic molecules in the context of membrane lipids?

    <p>'Water-loving' or polar headgroup molecules</p> Signup and view all the answers

    What characterizes phospholipids and sterols found in the plasma membrane?

    <p>'Water-loving' or polar headgroup and 'water-fearing' or non-polar tail</p> Signup and view all the answers

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