Cell Membrane Structure and Function
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Questions and Answers

What is the primary function of the phospholipid bilayer in the cell membrane?

  • To regulate the passage of molecules into and out of the cell. (correct)
  • To produce energy for the cell.
  • To provide structural support for the cell.
  • To store genetic information for the cell.

    • Why is the cell membrane described as a 'fluid mosaic'?

  • Because it is a fluid-like substance.
  • Because it is made up of a variety of different molecules. (correct)
  • Because it is constantly changing shape and composition. (correct)
  • Because it is composed of a mosaic of proteins and lipids. (correct)

    • What does the term 'semipermeable' mean in relation to the cell membrane?

  • The membrane allows only water molecules to pass through.
  • The membrane is completely impermeable to all molecules.
  • The membrane allows all molecules to pass through freely.
  • The membrane allows only certain types of molecules to pass through. (correct)

    • In which direction do molecules tend to move during diffusion?

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

    What is the primary difference between diffusion and osmosis?

    <p>Diffusion involves the movement of solutes across a membrane, while osmosis involves the movement of water molecules across a membrane.</p> Signup and view all the answers

    What happens to a cell placed in a hypertonic solution?

    <p>The cell will shrink and possibly die.</p> Signup and view all the answers

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

    <p>A hypertonic solution has a higher solute concentration than a hypotonic solution.</p> Signup and view all the answers

    What is the role of facilitated diffusion in membrane transport?

    <p>To provide a pathway for molecules to move passively across the membrane with the help of transport proteins.</p> Signup and view all the answers

    What is the main difference between diffusion and facilitated diffusion?

    <p>Diffusion does not require the assistance of membrane proteins, while facilitated diffusion does.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the phospholipid bilayer?

    <p>The lipid tails are hydrophilic.</p> Signup and view all the answers

    What is the primary function of the cell membrane?

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

    What is the term used to describe the arrangement of phospholipid molecules in the cell membrane?

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

    Which part of the phospholipid molecule is hydrophilic?

    <p>The phosphate head</p> Signup and view all the answers

    What does the fluid mosaic model explain about the cell membrane?

    <p>The dynamic nature of the cell membrane with embedded proteins</p> Signup and view all the answers

    What type of movement across the cell membrane does not require energy?

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

    What is the driving force behind the movement of molecules in diffusion?

    <p>Concentration gradient</p> Signup and view all the answers

    What happens to a plant cell placed in a hypotonic solution?

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

    Which of these is NOT a type of passive transport across the cell membrane?

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

    What is the role of proteins in facilitated diffusion?

    <p>To act as channels or carriers to help molecules cross the membrane.</p> Signup and view all the answers

    Study Notes

    Cell Membrane Structure

    • Cell membranes are composed of lipids and proteins.
    • They form a bilayer, with two layers of phospholipids arranged to face each other.
    • Phospholipids have hydrophilic heads (water-loving) and hydrophobic tails (water-fearing).
    • The heads face the watery environment inside and outside the cell.
    • The tails face away from the water and towards each other.

    Fluid Mosaic Model

    • The fluid mosaic model describes the structure of the cell membrane more accurately.
    • The membrane is fluid because the components (phospholipids and proteins) are not fixed in place but can move around.
    • The membrane is a mosaic because of the diverse components embedded within it.
    • The structure includes integral proteins, peripheral proteins, cholesterol, and glycoproteins/glycolipids.
    • The bilayer of phospholipids is the main component.

    Membrane Permeability

    • Cell membranes are semipermeable, meaning that they only allow certain substances to pass through.

    Passive Transport: Diffusion

    • Diffusion is the movement of liquid or gas molecules from an area of high concentration to an area of low concentration across a semipermeable membrane.
    • This is a passive process that does not require energy.

    Passive Transport: Osmosis

    • Osmosis is the diffusion of water across a semipermeable membrane.
    • Water moves from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration).

    Types of Solutions

    • Hypertonic solution: Contains a higher concentration of solutes than the cell. Water moves out of the cell, causing it to shrink (plasmolyze).
    • Hypotonic solution: Contains a lower concentration of solutes than the cell. Water moves into the cell, causing it to swell and potentially burst (lyse).
    • Isotonic solution: Contains the same concentration of solutes as the cell. There is no net movement of water.

    Active Transport

    • Active transport moves molecules against their concentration gradient (low to high).
    • This requires energy in the form of ATP.
    • The sodium-potassium pump is an example of active transport in cells.

    Bulk Transport

    • Bulk transport moves large molecules across the membrane.
    • Exocytosis: Releases large molecules out of the cell.
    • Endocytosis: Takes large molecules into the cell.
    • Types of Endocytosis includes Receptor-Mediated Endocytosis: takes specific molecules into the cell using receptors.

    Facilitated Diffusion

    • Facilitated diffusion moves molecules across the membrane using carrier proteins.
    • This is a passive transport method that doesn't require energy.

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    Related Documents

    Cell Membrane Notes PDF

    Description

    This quiz explores the structure, composition, and function of cell membranes, including the fluid mosaic model and membrane permeability. Test your understanding of key concepts such as phospholipids, passive transport, and diffusion. Ideal for biology students to reinforce their knowledge of cellular structures.

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