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Anatomy & Physiology: Membrane Transport and Neurons

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Termini in questo insieme (20)

  • What is the basic structure of the plasma membrane according to the fluid mosaic model?
    A phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails inward, embedded with integral and peripheral proteins, cholesterol, glycocalyx, and anchored by the cytoskeleton.
  • What are integral membrane proteins and their functions?
    Proteins that span the plasma membrane with hydrophilic and hydrophobic regions; they function as channels, carriers, enzymes, receptors, and in cell adhesion.
  • What is the glycocalyx and its role?
    A carbohydrate-rich 'sugar coating' on the outer plasma membrane surface that helps cells recognize each other and changes in cancer cells.
  • Name the three types of plasma membrane junctions and their functions.
    Tight junctions prevent molecule passage between cells; desmosomes anchor cells to resist mechanical stress; gap junctions allow cytoplasmic molecule passage for communication.
  • What is diffusion and what factors influence its rate?
    The movement of molecules from high to low concentration; influenced by concentration gradient slope, molecule size, and temperature.
  • What types of molecules can pass by simple diffusion through the plasma membrane?
    Nonpolar, lipid-soluble molecules like O2, CO2, fats, urea, and alcohol.
  • Describe facilitated diffusion.
    Passive transport of water-soluble molecules via specific carrier proteins or channels without ATP, moving down their concentration gradient.
  • What is osmosis and its importance in cells?
    Unassisted diffusion of water across a semipermeable membrane from high to low water concentration, crucial for fluid homeostasis.
  • Define osmolarity and tonicity and how they differ.
    Osmolarity is total solute particle concentration; tonicity is a solution's effect on cell shape by altering water content, depending on nonpenetrating solutes.
  • What happens to red blood cells in isotonic, hypertonic, and hypotonic solutions?
    Isotonic: no change; hypertonic: cells shrink (crenate); hypotonic: cells swell and may lyse (burst).
  • Why does active transport require ATP?
    Because substances are either too large, lipid-insoluble, or moving against their concentration gradients.
  • Describe the Na+/K+ ATPase pump and its function.
    An antiport pump that moves 3 Na+ ions out and 2 K+ ions into the cell against their gradients, maintaining essential ion concentrations and cell responsiveness.
  • What is the difference between primary and secondary active transport?
    Primary uses ATP directly (e.g., Na+/K+ pump); secondary uses energy from ion gradients created by primary transport to move other substances.
  • What are exocytosis and endocytosis?
    Exocytosis is vesicle fusion with the plasma membrane to release substances outside the cell; endocytosis is vesicle formation to bring substances into the cell.
  • Name and describe three types of endocytosis.
    Phagocytosis: engulfing large particles; pinocytosis: uptake of fluid and dissolved substances; receptor-mediated endocytosis: selective uptake of specific molecules.
  • What are the three functional regions of a neuron?
    Receptive region (dendrites), conducting region (axon), and secretory region (axon terminals).
  • What is the role of dendrites in neurons?
    Short, branched extensions that receive signals and conduct graded potentials toward the cell body.
  • Describe the axon and its importance.
    A long process arising from the axon hillock that conducts action potentials away from the cell body; conduction speed increases with diameter.
  • What is retrograde and anterograde transport in axons?
    Anterograde moves organelles and neurotransmitters from cell body to axon terminals; retrograde moves materials back for degradation or recycling.
  • How do viruses like rabies reach neuron cell bodies?
    By retrograde transport along the axon from the site of infection to the neuron cell body.