Cell Membranes and Transport Mechanisms
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Questions and Answers

What is diffusion?

  • The process of molecules moving from an area of high concentration to an area of low concentration. (correct)
  • The movement of water across a selectively permeable membrane.
  • The facilitated movement of glucose molecules through protein channels.
  • The transport of molecules against their concentration gradient using energy.

    • Which factor does NOT influence the rate of diffusion?

  • Temperature
  • Molecule size
  • Presence of water (correct)
  • Concentration gradient

    • How does osmosis relate to osmolality?

  • Higher osmolality in a solution leads to more water moving out of cells. (correct)
  • Osmosis is solely driven by the presence of permeable solutes.
  • Osmosis occurs when solute concentrations are equal.
  • Osmosis does not depend on the concentration of solutes in a solution.

    • What distinguishes primary active transport from secondary active transport?

    <p>Primary active transport requires ATP directly to transport molecules.</p> Signup and view all the answers

    What role does the lipid bilayer play in the cell membrane?

    <p>It serves as a barrier that regulates the passage of substances.</p> Signup and view all the answers

    Which type of transport requires energy to move substances against their concentration gradient?

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

    What distinguishes primary active transport from secondary active transport?

    <p>It directly uses ATP to move ions.</p> Signup and view all the answers

    Which of the following processes is NOT a form of passive transport?

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

    Endocytosis is best described as which of the following?

    <p>The process where cells engulf materials from their external environment.</p> Signup and view all the answers

    Which method of transport would most likely be used by cells when absorbing large particles?

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

    Study Notes

    Cell Membranes

    • Composed of a lipid bilayer, proteins, and carbohydrates.
    • Selectively permeable: Allows some molecules to pass through while blocking others.

    Simple Diffusion

    • Movement of molecules from an area of high concentration to an area of low concentration.
    • Does not require energy.
    • Influenced by:
      • Concentration gradient: Larger gradient, faster diffusion.
      • Temperature: Higher temperature, faster diffusion.
      • Molecular size: Smaller molecules, faster diffusion.
      • Membrane permeability: More permeable membrane, faster diffusion.

    Facilitated Diffusion

    • Movement of molecules across a membrane with the help of protein carriers or channels.
    • Does not require energy.
    • Specific for certain molecules.

    Osmosis

    • Diffusion of water across a selectively permeable membrane from a region of high water concentration to a region of low water concentration.
    • Driven by the difference in water potential between the two regions.
    • Influenced by:
      • Concentration of solutes: Higher solute concentration, lower water potential.
      • Temperature: Higher temperature, faster osmosis.

    Osmolality

    • Measure of the solute concentration of a solution.
    • Determines the movement of water across a membrane.

    Active Transport

    • Movement of molecules across a membrane against their concentration gradient.
    • Requires energy.
    • Primary active transport: Directly uses ATP (energy) to transport molecules.
    • Secondary active transport: Uses the energy stored in the electrochemical gradient of one molecule to transport another molecule.
    • Endocytosis and exocytosis: Forms of active transport where the cell engulfs or releases large molecules using membrane-bound vesicles.

    Electrochemical Gradient

    • Combination of electrical and chemical gradients for an ion.
    • Influences the movement of ions across a membrane.
    • Potential difference across a membrane alters the rate of diffusion.

    Significance of Transport Mechanisms

    • Diffusion: Essential for gas exchange in the lungs, nutrient uptake in the intestines, and waste removal in the kidneys.
    • Facilitated diffusion: Facilitates the rapid uptake of glucose into cells, allows for the transport of ions across membranes.
    • Active transport: Maintains the concentration gradients of essential ions like sodium and potassium, allowing muscle contraction and nerve impulse transmission.
    • Osmosis: Plays a vital role in maintaining cell volume and shape, regulating blood pressure, and filtering waste products in the kidneys.

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    Transport Across Cell Membrane PDF

    Description

    This quiz covers the structure and function of cell membranes, including lipid bilayers, proteins, and carbohydrates. It explores processes such as simple diffusion, facilitated diffusion, and osmosis, detailing how substances move across cell membranes. Test your understanding of these vital biological concepts.

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