Isotonic, Hypotonic, and Hypertonic Solutions
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Questions and Answers

What is the primary function of the hydrophilic regions of proteins in the membrane?

  • To expose themselves to water (correct)
  • To flip-flop transversely across the membrane
  • To facilitate lateral movement of proteins
  • To interact with the hydrophobic tails of phospholipids

    • Which of the following is NOT a function of the cell membrane?

  • Regulating cell growth (correct)
  • Maintaining ion concentrations of various substances
  • Controlling incoming and outgoing substances
  • Protecting the cell

    • What is the average frequency of a phospholipid molecule flip-flopping across the membrane?

  • Once per month (correct)
  • Once per year
  • Once per minute
  • Once per second

    • What is the term for the ability of the cell membrane to allow certain molecules to pass through while keeping others out?

    <p>Selective permeability</p> Signup and view all the answers

    What is the main component of the cell membrane that helps to maintain its fluidity?

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

    What is the primary function of the plasma membrane?

    <p>To separate the living cell from its surroundings</p> Signup and view all the answers

    What is the term for the movement of proteins and lipids within the membrane?

    <p>Lateral movement</p> Signup and view all the answers

    What is the major role of the cell membrane in maintaining homeostasis?

    <p>All of the above</p> Signup and view all the answers

    What is the term used to describe the ability of the plasma membrane to allow some substances to cross it more easily than others?

    <p>Selective permeability</p> Signup and view all the answers

    What is the most abundant lipid in the plasma membrane?

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

    What is the model that describes the structure of the cell membrane?

    <p>Fluid Mosaic Model</p> Signup and view all the answers

    What is the term used to describe the structure of phospholipids?

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

    What is the name of the model that describes the plasma membrane as a fluid structure with a mosaic of proteins embedded in it?

    <p>Fluid mosaic model</p> Signup and view all the answers

    Who proposed the sandwich model of the plasma membrane?

    <p>Hugh Davson and James Danielli</p> Signup and view all the answers

    What is the main criticism of the sandwich model of the plasma membrane?

    <p>It does not account for the placement of membrane proteins</p> Signup and view all the answers

    In a hypotonic solution, what is the concentration of solutes compared to inside the cell?

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

    What is the function of the integral proteins in the plasma membrane?

    <p>To regulate the movement of substances into and out of the cell</p> Signup and view all the answers

    What happens to a cell in a hypotonic solution?

    <p>It swells and bursts open</p> Signup and view all the answers

    What is the direction of water movement in a hypertonic solution?

    <p>From inside the cell to the solution</p> Signup and view all the answers

    What is the result of a cell in an isotonic solution?

    <p>It stays the same</p> Signup and view all the answers

    What is the main reason for water movement in osmosis?

    <p>Solute concentration difference</p> Signup and view all the answers

    What is the term for the bursting of a cell due to excessive water uptake?

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

    What happens to the cell membrane in a hypertonic solution?

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

    What is the main difference between a hypotonic and a hypertonic solution?

    <p>Solute concentration</p> Signup and view all the answers

    What is the primary characteristic of passive transport?

    <p>It does not use energy from the cell.</p> Signup and view all the answers

    What is the net direction of solute movement in diffusion through a membrane?

    <p>From an area of high concentration to an area of low concentration.</p> Signup and view all the answers

    What is the purpose of proteins in facilitated diffusion?

    <p>To carry polar molecules or ions across the membrane.</p> Signup and view all the answers

    What is the state of the molecules in a system at equilibrium?

    <p>They are evenly spaced, but still moving randomly.</p> Signup and view all the answers

    What is the primary difference between simple diffusion and facilitated diffusion?

    <p>The use of proteins to facilitate molecule movement.</p> Signup and view all the answers

    What is the result of diffusion continuing until all molecules are evenly spaced?

    <p>The molecules will continue to move, but will be evenly spaced.</p> Signup and view all the answers

    What is the characteristic of molecules that allows them to move from an area of high concentration to an area of low concentration?

    <p>Their kinetic energy.</p> Signup and view all the answers

    What is the term for the movement of molecules from an area of high concentration to an area of low concentration?

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

    What is the primary driving force for osmosis?

    <p>The concentration gradient of water across a membrane</p> Signup and view all the answers

    In a hypotonic solution, what happens to the cell?

    <p>The cell will swell due to water gain</p> Signup and view all the answers

    What is the term for a solution that has the same concentration of solutes as the cell?

    <p>Isotonic solution</p> Signup and view all the answers

    What happens to the cell in a hypertonic solution?

    <p>The cell will shrink due to water loss</p> Signup and view all the answers

    What is the role of solutes in osmosis?

    <p>Solutes attract water molecules, causing them to move towards areas of high solute concentration</p> Signup and view all the answers

    What is the term for the movement of water across a selectively permeable membrane?

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

    What is the result of a cell in an isotonic solution?

    <p>The cell will remain the same size</p> Signup and view all the answers

    What is the term for the state of equal water movement in both directions across a membrane?

    <p>Dynamic equilibrium</p> Signup and view all the answers

    Study Notes

    Cell Equilibrium and Osmosis

    • In a state of equilibrium, water flows in both directions across the cell membrane, and solute and water concentrations are equal inside and outside the cell.
    • Hypotonic solution: has a lower concentration of solutes and a higher concentration of water than inside the cell, resulting in water moving into the cell, causing it to swell and potentially burst (cytolysis).
    • Hypertonic solution: has a higher concentration of solutes and a lower concentration of water than inside the cell, resulting in water moving out of the cell, causing it to shrink (plasmolysis).

    Cell Membrane Structure and Function

    • The plasma membrane is a selective barrier between the cell and its surroundings, controlling the movement of substances in and out of the cell.
    • Phospholipids are the most abundant lipid in the plasma membrane, and are amphipathic molecules with hydrophobic and hydrophilic regions.
    • The fluid mosaic model describes the plasma membrane as a fluid structure with embedded proteins, allowing for selective permeability.

    Functions of Membranes

    • Protect the cell
    • Control the movement of substances in and out of the cell
    • Maintain ion concentrations and homeostasis
    • Selectively permeable, allowing some molecules to pass through while keeping others out

    Phospholipid Bilayer and Fluidity

    • Phospholipids in the plasma membrane can move laterally within the bilayer
    • Rarely do molecules flip-flop transversely across the membrane
    • The fluidity of the membrane allows for the lateral movement of lipids and proteins

    Transport Across Membranes

    Passive Transport

    • Diffusion: the random movement of particles from an area of high concentration to an area of low concentration
    • Osmosis: the diffusion of water across a selectively permeable membrane, moving from high to low water concentration
    • Facilitated diffusion: the use of proteins to carry polar molecules or ions across the membrane

    Active Transport

    • Requires energy from the cell
    • Examples include protein pumps, endocytosis, and exocytosis

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    Description

    This quiz covers the concept of equilibrium in cells, and the movement of water in and out of cells in different solutions. It includes isotonic, hypotonic, and hypertonic solutions.

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