Biology Chapter 7 Flashcards
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Questions and Answers

Which of the following statements about a typical plasma membrane is correct?

  • The two sides of the plasma membrane have different lipid and protein composition. (correct)
  • The plasma membrane is entirely composed of carbohydrates.
  • The two sides of the membrane have the same lipid and protein composition.
  • All membrane functions are the same on both sides.

    • Which of the following best describes the structure of a biological membrane?

  • Two layers of phospholipids with proteins either crossing the layers or on the surface of the layers. (correct)
  • A single layer of phospholipids.
  • A rigid protein layer.
  • A carbohydrate-based membrane.

    • The permeability of a biological membrane to a specific polar solute may depend on which of the following?

  • Temperature.
  • The presence of covalent bonds.
  • The surface area of the membrane.
  • The types of transport proteins in the membrane. (correct)

    • Which of the following is least likely to be important in holding the components of a biological membrane together?

    <p>Covalent interactions between the phospholipid and protein components of the membrane.</p> Signup and view all the answers

    What makes the structure of the plasma membrane selectively permeable?

    <p>The hydrophobic nature of the lipid bilayer.</p> Signup and view all the answers

    Which of these cannot rapidly pass directly through the phospholipids of the plasma membrane?

    <p>Ions and hydrophilic molecules</p> Signup and view all the answers

    What is referred to as selective permeability in a plasma membrane?

    <p>The ability to pass some solutes while blocking others.</p> Signup and view all the answers

    What will occur to a red blood cell placed in a 3.21% (m/v) NaCl solution?

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

    Which factor does not affect membrane permeability?

    <p>The polarity of membrane phospholipids.</p> Signup and view all the answers

    How can a lipid be distinguished from a sugar?

    <p>Lipids are mostly nonpolar, whereas sugars are polar.</p> Signup and view all the answers

    Osmosis is a type of diffusion.

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

    What property of dishwashing liquid makes it useful to wash grease from pans?

    <p>Amphipathic nature.</p> Signup and view all the answers

    Which of the following particles could diffuse easily through a cell membrane?

    <p>Oxygen (O2)</p> Signup and view all the answers

    The water-soluble portion of a phospholipid is the polar head.

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

    If a red blood cell bursts in a salt solution, what is the tonicity of the solution?

    <p>Hypotonic.</p> Signup and view all the answers

    Which statement about osmosis is correct?

    <p>The presence of aquaporins should speed up the process of osmosis.</p> Signup and view all the answers

    In facilitated diffusion, what is the role of the transport protein?

    <p>Transport proteins provide a hydrophilic route for the solute to cross the membrane.</p> Signup and view all the answers

    What cycle does active transport by the sodium-potassium pump follow?

    <p>Three Na+ ions bind, are phosphorylated, and three Na+ are released outside.</p> Signup and view all the answers

    Which of the following statements correctly describes the driving forces for diffusion of Na+ and K+ ions?

    <p>Na+ diffusion is facilitated by the Na+ concentration gradient.</p> Signup and view all the answers

    What is the mechanism of glucose uptake in animal cells?

    <p>Cotransport with Na+ ions.</p> Signup and view all the answers

    What distinguishes facilitated diffusion from simple diffusion?

    <p>Membrane proteins help move molecules across the membrane.</p> Signup and view all the answers

    Which transporter does not use passive transport?

    <p>Sodium-Potassium Pump</p> Signup and view all the answers

    Active transport does not require energy.

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

    What is the role of transporter proteins in glucose movement across a membrane?

    <p>Transporters assist in the movement of glucose from higher to lower concentration.</p> Signup and view all the answers

    What is typically true about the net movement of an ion across a membrane by passive diffusion?

    <p>Ions tend to move towards regions of unlike charge.</p> Signup and view all the answers

    During active transport via the sodium-potassium pump, ATP hydrolysis pumps three sodium ions into the cell.

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

    What type of transport is used to move lactose into the cell when its concentration is higher inside?

    <p>Active transport.</p> Signup and view all the answers

    How can the cell increase phosphate concentration in the cytosol when it is lower outside?

    <p>Active transport.</p> Signup and view all the answers

    What is the mechanism of glucose movement against a concentration gradient?

    <p>Cotransport with Na+ ions.</p> Signup and view all the answers

    How do active and passive transport differ?

    <p>Active transport requires energy whereas passive does not.</p> Signup and view all the answers

    What happens during endocytosis?

    <p>Substances are taken into the cell by folding in of the plasma membrane.</p> Signup and view all the answers

    Which movement is due to osmosis when a plant cell is placed in concentrated salt water?

    <p>Water moves out of the cell.</p> Signup and view all the answers

    What affects the rate of osmotic movement of water?

    <p>Differences in solute concentrations.</p> Signup and view all the answers

    What occurs when solutions reach osmotic equilibrium?

    <p>There is no net movement of water across the membrane.</p> Signup and view all the answers

    Study Notes

    Plasma Membrane Structure and Composition

    • Plasma membranes have distinct lipid and protein compositions on either side, facilitating different functions for the cytoplasmic and exterior surfaces.
    • Composed of two layers of phospholipids with proteins embedded or attached to the bilayer, providing structural complexity and functionality.

    Membrane Permeability

    • Membrane permeability for polar solutes depends on the presence of specific transport proteins, as the lipid bilayer is generally impermeable to polar or charged substances.
    • Small nonpolar molecules, e.g., O2 and CO2, can diffuse directly through the bilayer, while ions and larger polar molecules require transport proteins.
    • Water molecules can pass through the membrane slowly but efficiently via aquaporins, specialized transport proteins.

    Tonicity and Effects on Cells

    • Crenation occurs when a red blood cell shrinks in a hypertonic solution (e.g., 3.21% NaCl), while hemolysis is the bursting of a cell in a hypotonic solution (e.g., distilled water).
    • Solutions classified as isotonic to red blood cells (e.g., 0.9% NaCl) maintain cell shape.

    Mechanisms of Transport

    • Simple diffusion is the process by which small, nonpolar molecules pass through the membrane without assistance.
    • Facilitated diffusion employs transport proteins to help molecules cross, while active transport requires ATP to move substances against their concentration gradient.
    • The sodium-potassium pump is crucial for maintaining Na+ low within cells and K+ high, pumping three Na+ out for every two K+ in.

    Energetics of Transport

    • Active transport mechanisms use energy (e.g., from ATP hydrolysis) to move substances against their electrochemical gradient, including the cotransport of glucose with sodium ions.
    • Osmosis, the diffusion of water, can occur even when solutes cannot cross the membrane, with water moving toward higher solute concentration until equilibrium is reached.

    Special Transport Mechanisms

    • Endocytosis and exocytosis involve vesicles that transport substances without them crossing the membrane directly.
    • Micelles formed by detergents illustrate how amphipathic molecules can encapsulate grease and eliminate it through washing.

    Concentration Gradients and Transport

    • An electrochemical gradient influences ion movement, with Na+ favoring entry and K+ favoring exit, but inhibited by charge differences.
    • The rate of osmotic movement is affected by temperature, pressure, and the concentration gradient of solutes across a selectively permeable membrane.

    Osmotic Equilibrium

    • At osmotic equilibrium, water molecules remain in dynamic equilibrium, with continuous movement but no net directional flow across the membrane.

    Key Transport Proteins

    • Specific transporters such as GLUT-1 facilitate glucose diffusion, exemplifying facilitated diffusion, while the sodium-potassium pump exemplifies active transport requiring ATP.

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    Test your knowledge of the concepts in Chapter 7 of Mastering Biology with these flashcards. Focus on the structure and functions of biological membranes, including the differences in lipid and protein composition. Perfect for reinforcing your understanding of plasma membranes!

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