Diffusion and osmosis
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Questions and Answers

What is the direction of net movement of molecules in osmosis?

  • From a region of low solute concentration to a region of high solute concentration
  • Along a concentration gradient
  • From a region of high solute concentration to a region of low solute concentration (correct)
  • Against a concentration gradient

    • What is the primary reason for the movement of molecules in osmosis?

  • Kinetic energy of random motion (correct)
  • Electrostatic attraction
  • Difference in pressure
  • Difference in temperature

    • What determines the direction of diffusion in osmosis?

  • Temperature difference
  • Relative solute concentrations (correct)
  • Pressure difference
  • Electrostatic charge

    • What is tonicity?

    <p>The relative solute concentrations of two solutions</p> Signup and view all the answers

    What is a hypertonic solution?

    <p>A solution with a high solute concentration</p> Signup and view all the answers

    What happens to the free water concentration when the solute concentration increases?

    <p>It decreases</p> Signup and view all the answers

    What is homeostasis?

    <p>A self-regulatory process by which biological systems tend to maintain stability</p> Signup and view all the answers

    Why is movement regulated in cellular membranes?

    <p>Because cellular membranes are selectively permeable</p> Signup and view all the answers

    What is the purpose of the dialysis bag in the lab?

    <p>To act as a selectively permeable membrane</p> Signup and view all the answers

    Why do NH3 molecules diffuse faster than HCl molecules?

    <p>Because they are lighter</p> Signup and view all the answers

    What is the main function of aquaporins?

    <p>To allow water to pass through the membrane</p> Signup and view all the answers

    How do larger molecules, such as carbohydrates, pass through the membrane?

    <p>By transport proteins via active or passive transport</p> Signup and view all the answers

    What happens when gaseous NH3 and HCl collide?

    <p>They form a white precipitate</p> Signup and view all the answers

    Why do plant cells not burst in a hypotonic solution?

    <p>Because they have a cell wall</p> Signup and view all the answers

    What is the difference between active and passive transport?

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

    What is the function of the cell wall in plant cells?

    <p>To provide structural support</p> Signup and view all the answers

    What is diffusion?

    <p>The movement of molecules with a concentration gradient</p> Signup and view all the answers

    What is osmosis?

    <p>The movement of water through a phospholipid bilayer</p> Signup and view all the answers

    What happens to a protoplast in a hypotonic solution?

    <p>It expands</p> Signup and view all the answers

    Why is it necessary for cells to move materials through plasma membranes?

    <p>To maintain homeostasis</p> Signup and view all the answers

    What is the purpose of the fume cupboard or fume hood?

    <p>To provide a safe environment for gas diffusion</p> Signup and view all the answers

    What is the difference between a plant cell and a protoplast?

    <p>The presence of a cell wall</p> Signup and view all the answers

    What is the characteristic of a hypertonic solution?

    <p>More free water out of the cell than in the cell</p> Signup and view all the answers

    What happens to an animal cell in a hypertonic solution?

    <p>It becomes shriveled or crenated</p> Signup and view all the answers

    What is an example of an isotonic solution?

    <p>Normal saline</p> Signup and view all the answers

    What is the effect of temperature on the rate of diffusion?

    <p>It increases the rate of diffusion</p> Signup and view all the answers

    What is the characteristic of a hypotonic solution?

    <p>More free water in the cell than out of the cell</p> Signup and view all the answers

    What happens to a plant cell in a hypertonic solution?

    <p>It becomes plasmolyzed</p> Signup and view all the answers

    What is the effect of mass of particle on the rate of diffusion?

    <p>It decreases the rate of diffusion</p> Signup and view all the answers

    What is the characteristic of an isotonic solution?

    <p>Equal free water and solutes in and out of the cell</p> Signup and view all the answers

    Study Notes

    Homeostasis and Cell Membranes

    • Homeostasis is a self-regulatory process that maintains stability in biological systems while adjusting to optimal conditions for survival.
    • Cells maintain homeostasis by moving materials through plasma membranes into and out of the cytoplasm.
    • Cellular membranes are selectively permeable, consisting of phospholipid bilayers with embedded proteins.
    • Phospholipid fatty acids are hydrophobic, limiting the movement of water.

    Water and Molecule Transport

    • Water can pass through the membrane by: • Freely by osmosis (small amount) • Selectively by aquaporins (large amount)
    • Molecules can pass through the membrane by: • Most ions moving through protein channels • Larger molecules carried by transport proteins via active or passive transport

    Active and Passive Transport

    • Active transport requires transport proteins, energy output, and moves against a concentration gradient.
    • Passive transport does not require energy and moves along the concentration gradient, including diffusion and osmosis.

    Diffusion and Osmosis

    • Diffusion is the net movement of molecules or atoms down/along a concentration gradient.
    • Osmosis is a type of diffusion that involves the net movement of solvent from a region of low solute concentration to a region of high solute concentration.

    Tonicity

    • Tonicity refers to the relative solute concentrations of two solutions separated by a semipermeable membrane.
    • A solution can be hypertonic, isotonic, or hypotonic.
    • Hypertonic solution: [free water in cell] > [free water out of cell], [solutes in cell] < [solutes out of cell]
    • Isotonic solution: [free water in cell] = [free water out of cell], [solutes in cell] = [solutes out of cell]
    • Hypotonic solution: [free water in cell] < [free water out of cell], [solutes in cell] > [solutes out of cell]

    Effects of Tonicity on Cells

    • In a hypertonic solution, animal cells shrink or become crenated, while plant cells become plasmolyzed.
    • In an isotonic solution, animal cells remain normal, while plant cells become flaccid.
    • In a hypotonic solution, animal cells lyse or burst, while plant cells become normal or turgid.

    Factors Influencing Diffusion

    • The rate of diffusion is influenced by: • Mass of particle: ↑mass of particle = ↓rate of diffusion • Temperature: ↑temperature = ↑rate of diffusion

    Practical Investigation

    • The lab will investigate: • Diffusion of gases • Osmosis (diffusion of molecules through a selectively permeable membrane) • Osmotic behavior in plant cells

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