Cytoskeleton and Its Components
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Cytoskeleton and Its Components

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Questions and Answers

What is the primary function of cholesterol molecules in the cell membrane?

  • Catalyze production of enzymes
  • Maintain membrane fluidity (correct)
  • Form hydrogen bonds with water
  • Facilitate passive transport

    • Which term describes the movement of water across a selectively permeable membrane?

  • Active transport
  • Endocytosis
  • Facilitated diffusion
  • Osmosis (correct)

    • What type of transport moves molecules against their concentration gradient?

  • Active transport (correct)
  • Facilitated diffusion
  • Diffusion
  • Passive transport

    • Which of the following correctly describes passive transport?

    <p>Moves substances from high to low concentration</p> Signup and view all the answers

    What is the role of glycoproteins in the cell membrane?

    <p>Identify cell type</p> Signup and view all the answers

    Which of the following is NOT a method of molecule movement into cells?

    <p>Diffusion through solid barriers</p> Signup and view all the answers

    Which of these statements is true regarding diffusion?

    <p>It results in the equalization of concentrations.</p> Signup and view all the answers

    What drives passive transport mechanisms?

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

    What are the main components of the cytoskeleton?

    <p>Microfilaments, Microtubules, Intermediate filaments</p> Signup and view all the answers

    Which function is NOT attributed to the cytoskeleton?

    <p>Energy production</p> Signup and view all the answers

    Which characteristic distinguishes intermediate filaments from microfilaments and microtubules?

    <p>Size range between microfilaments and microtubules</p> Signup and view all the answers

    What type of filament is primarily involved in muscle contractions?

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

    Which function is associated with microtubules?

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

    Which structural component forms the main barrier of the cell membrane?

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

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

    <p>Synthesizing proteins</p> Signup and view all the answers

    What type of movement do cilia facilitate?

    <p>Wave-like motion</p> Signup and view all the answers

    What is the primary function of active transport?

    <p>To move substances against their concentration gradient using energy</p> Signup and view all the answers

    Which type of endocytosis specifically involves the engulfing of large particles?

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

    What role do protein pumps play in cellular processes?

    <p>They require energy to move substances across membranes</p> Signup and view all the answers

    What occurs during exocytosis?

    <p>The cell releases large molecules by discharging material</p> Signup and view all the answers

    Which of the following statements about receptor-mediated endocytosis is accurate?

    <p>It involves the specific uptake of molecules via receptors</p> Signup and view all the answers

    What distinguishes facilitated diffusion from simple diffusion?

    <p>Facilitated diffusion requires carrier proteins.</p> Signup and view all the answers

    Which of the following best describes osmosis?

    <p>The movement of water through a permeable membrane to a higher concentration of solutes.</p> Signup and view all the answers

    What requirement does facilitated diffusion have that simple diffusion does not?

    <p>Carrier proteins</p> Signup and view all the answers

    What happens to a cell in a hypotonic solution?

    <p>The cell swells and may burst due to excess water intake.</p> Signup and view all the answers

    What primarily drives the process of diffusion?

    <p>The need for balance in solute concentrations.</p> Signup and view all the answers

    How does a hypertonic solution affect a cell?

    <p>Water exits the cell, causing it to shrink.</p> Signup and view all the answers

    What type of molecules typically undergo facilitated diffusion?

    <p>Larger polar molecules</p> Signup and view all the answers

    Which of the following statements about facilitated diffusion is false?

    <p>It is an active transport mechanism.</p> Signup and view all the answers

    What occurs when a cell is placed in an isotonic solution?

    <p>No net movement of water occurs.</p> Signup and view all the answers

    What happens to a cell in a hypotonic solution?

    <p>Water diffuses into the cell, potentially causing it to swell.</p> Signup and view all the answers

    In which type of solution does water diffuse out of the cell?

    <p>Hypertonic solution.</p> Signup and view all the answers

    What is required for active transport to occur?

    <p>Chemical energy from ATP.</p> Signup and view all the answers

    What is the main characteristic of a hypertonic solution?

    <p>High concentration of solutes relative to another solution.</p> Signup and view all the answers

    Which solution will cause a cell to burst due to excess water intake?

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

    What does active transport create in the cell membrane?

    <p>A charge gradient.</p> Signup and view all the answers

    When a cell is in an isotonic environment, what happens to its volume?

    <p>It remains constant.</p> Signup and view all the answers

    Study Notes

    Cytoskeleton

    • A microscopic network of protein filaments and tubules in the cytoplasm
    • Consists of three main types of filaments, which are elongated chains of protein:
      • Microfilaments
      • Microtubules
      • Intermediate Filaments
    • Supports the cell, gives the cell its shape, and facilitates movement
    • Plays important roles in molecule transport and cell division

    Microfilaments

    • Primarily composed of the protein actin
    • Involved in multiple cellular processes, including:
      • Cytokinesis (cytoplasm division)
      • Cell motility
      • Cytoplasmic streaming
      • Muscle contractions
      • Maintenance of cell shape

    Microtubules

    • Involved in a variety of important cellular processes, including:
      • Chromosome division during cell division
      • Transporting molecules within the cell
      • Maintenance of cell shape
      • Cell motility

    Cilia and Flagella

    • Flagella are "tails" that propel a cell forward
    • Cilia are cellular appendages that allow the cell to move

    Intermediate Filaments

    • Intermediate in size between microfilaments and microtubules (8-10 nm)
    • Composed of various proteins like keratin, vimentin, desmin, and lamin
    • Play a crucial role in maintaining cell shape
    • Provide structural support by bearing tension

    Cell Membrane

    • Also known as the plasma membrane
    • Encloses the cell and its organelles
    • Phospholipids form the basic structure of the cell membrane, creating a lipid bilayer with embedded proteins
    • Involved in five key functions:
      • Protects the cell by acting as a barrier
      • Regulates transport of substances into and out of the cell
      • Receives chemical messengers from other cells
      • Acts as a receptor
      • Cell mobility, secretions, and absorptions of substances

    Structure of the Cell Membrane

    • Contains various components that aid in its function:
      • Channels or transporters: move molecules in one direction
      • Receptors: recognize specific chemicals
      • Cholesterol molecules: keeps the membrane fluid consistent
      • Enzymes: catalyze production of substances
      • Glycoproteins: identify cell type

    Phospholipids in the Cell Membrane

    • Have a hydrophilic (head) and hydrophobic (tail)
    • Hydrophilic head has affinity for water
    • Hydrophobic tail repels water
    • This interaction of phospholipids with water is crucial for life

    Movement Across the Plasma Membrane

    • Some molecules can move across the cell membrane without assistance:
      • Water, Carbon dioxide, Ammonia, Oxygen
    • Other molecules need different transport mechanisms:

    Methods of Molecule Movement into Cells

    • Passive transport: moves chemicals from high to low concentration (does not require energy)
    • Active transport: moves chemicals from low to high concentration (requires energy, uses protein pumps)
    • Endocytosis: movement of large materials into cells
    • Exocytosis: movement of large materials out of the cells

    Passive Transport

    • Moves chemicals down their concentration gradient
    • Three types of passive transport:
      • Diffusion
      • Facilitated Diffusion
      • Osmosis

    Diffusion

    • Movement of molecules from high concentration to low concentration to equalize concentration
    • Requires no energy
    • Driven by the existing concentration gradient

    Facilitated Diffusion

    • Passive transport of molecules or ions through specific transmembrane integral proteins
    • Does not require energy but needs carrier proteins
    • Moves molecules from high to low concentration

    Osmosis

    • Movement of water across a semipermeable membrane
    • Water moves from a dilute solution to a concentrated solution
    • Important for water movement in and out of cells

    Osmosis vs Diffusion

    • Osmosis is the movement of solvent particles (water molecules)
    • Diffusion is the movement of particles (like oxygen)

    Hypotonic, Hypertonic, and Isotonic Solutions

    • Hypotonic: lower solute concentration than the cell, water moves into the cell, causing it to swell
    • Hypertonic: higher solute concentration than the cell, water moves out of the cell, causing it to shrink
    • Isotonic: equal solute concentration inside and outside the cell, water moves in and out at the same rate, equilibrium

    Active Transport

    • Moves chemicals against their concentration gradient
    • Requires energy to move chemicals from low to high
    • Creates a charge gradient across the cell membrane
    • Requires protein pumps to move chemicals

    Endocytosis

    • Movement of large materials into cells
    • Three types of endocytosis:
      • Bulk-phase (non-specific)
      • Receptor-mediated (specific)
      • Receptor-mediated endocytosis uses phagocytosis and pinocytosis processes

    Receptor-Mediated Endocytosis

    • How cells take in specific molecules by binding to receptors on the cell surface

    Phagocytosis

    • "Cell eating"
    • Engulfing large particles or organisms by the cell

    Pinocytosis

    • "Cell drinking"
    • Engulfing dissolved materials by the cell

    Exocytosis

    • The reverse of endocytosis
    • Cell discharges materials
    • Vesicle containing the material moves to cell surface
    • Membrane of vesicle fuses with cell membrane
    • Materials are expelled outside the cell.

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