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Anatomy & Physiology: Cell Structure and Membrane Transport

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이 집합의 용어 (21)

  • What are the three basic parts of a human cell?
    Plasma membrane (flexible outer boundary), cytoplasm (intracellular fluid with organelles), and nucleus (DNA-containing control center).
  • Describe the structure of the plasma membrane.
    A fluid mosaic model with a bilayer of phospholipids, embedded proteins, and cholesterol that controls what enters and leaves the cell.
  • What are the characteristics of phospholipids in the membrane?
    Phosphate heads are polar and hydrophilic, fatty acid tails are nonpolar and hydrophobic, with cholesterol increasing membrane stiffness.
  • What roles do membrane proteins play?
    They function as transport proteins, enzymes, receptors, motor proteins, and in cell-to-cell connections.
  • Differentiate between integral and peripheral membrane proteins.
    Integral proteins span the membrane and include transporters; peripheral proteins are loosely attached and assist enzymes and shape changes.
  • What is selective permeability of the plasma membrane?
    The membrane allows some substances to enter or exit while blocking others, maintaining internal cell environment.
  • Define simple diffusion.
    Movement of nonpolar, lipid-soluble molecules directly through the lipid bilayer from high to low concentration.
  • What is facilitated diffusion?
    Passive transport of hydrophilic molecules across the membrane via carrier or channel proteins down their concentration gradient.
  • Explain carrier-mediated facilitated diffusion.
    Specific large polar molecules bind to transmembrane carriers that change shape to transport them across the membrane.
  • What are channel-mediated facilitated diffusion channels?
    Transmembrane proteins with aqueous cores that allow ions to pass based on size and charge; can be leakage or gated channels.
  • Describe osmosis in the context of the plasma membrane.
    Movement of water through a selectively permeable membrane via aquaporins, from low to high solute concentration.
  • What is tonicity and its effect on red blood cells?
    Tonicity is a solution's ability to change cell shape by altering water volume; isotonic is normal, hypertonic causes shrinking, hypotonic causes swelling.
  • What distinguishes active membrane transport from passive transport?
    Active transport requires ATP to move solutes against their concentration gradient; passive transport does not require energy.
  • Describe the sodium-potassium pump function.
    An ATPase enzyme pumps 3 Na+ out and 2 K+ into the cell, maintaining electrochemical gradients essential for excitable cells.
  • What is secondary active transport?
    Uses energy stored in ion gradients created by primary active transport to move other solutes against their gradients.
  • What is vesicular transport?
    Movement of large substances across membranes inside vesicles, requiring ATP; includes endocytosis, exocytosis, and transcytosis.
  • Explain endocytosis and its types.
    Process of bringing substances into the cell via vesicles; includes phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis.
  • What is phagocytosis?
    Engulfing solid particles by pseudopods forming a phagosome; used by macrophages and some white blood cells.
  • Describe pinocytosis.
    Nonspecific uptake of extracellular fluid and solutes by plasma membrane infolding; main nutrient absorption method in the small intestine.
  • What is receptor-mediated endocytosis?
    Selective uptake of molecules binding to specific membrane receptors, such as hormones and cholesterol complexes.
  • How does exocytosis work?
    Vesicles fuse with the plasma membrane to eject substances like hormones and neurotransmitters, triggered by cell signals.