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Anatomy & Physiology: Cell Structure and Membrane Transport

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Terms in this set (20)

  • What are the three basic parts of a human cell?
    Plasma membrane: flexible outer boundary, Cytoplasm: intracellular fluid with organelles, Nucleus: DNA-containing control center.
  • Describe the structure of the plasma membrane.
    A fluid mosaic model with a bilayer of phospholipids and embedded proteins, including cholesterol for stiffness.
  • What are the characteristics of phospholipids in the membrane?
    Phosphate heads are polar and hydrophilic, fatty acid tails are nonpolar and hydrophobic.
  • What roles do membrane proteins play?
    They function as transport proteins, enzymes, receptors, and cell-to-cell connectors.
  • What is selective permeability of the plasma membrane?
    Allows nutrients in, wastes out, and prevents unwanted substances from entering due to its hydrophobic core.
  • What is simple diffusion?
    Movement of nonpolar, lipid-soluble substances directly through the lipid bilayer down their concentration gradient.
  • What is facilitated diffusion?
    Passive transport of hydrophobic molecules via carrier or channel proteins down their concentration gradient.
  • How do carrier proteins work in facilitated diffusion?
    They bind specific molecules, change shape, and transport them across the membrane.
  • What are channel proteins and their types?
    Transmembrane proteins with aqueous cores; types include leakage channels (always open) and gated channels (controlled opening).
  • What is osmosis?
    Diffusion of water through a selectively permeable membrane via lipid bilayer or aquaporins.
  • Define tonicity and its effects on red blood cells.
    Isotonic: normal shape, Hypertonic: cell shrinks (crenation), Hypotonic: cell swells and may burst (lysis).
  • What distinguishes active membrane transport from passive transport?
    Active transport requires ATP energy to move solutes against their concentration gradient.
  • What is the function of the sodium-potassium pump?
    Pumps 3 Na+ out and 2 K+ in, 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.
  • What is vesicular transport?
    Movement of large substances across membranes inside vesicles, requiring ATP.
  • Name the three types of vesicular transport.
    Transcytosis, Endocytosis (phagocytosis, pinocytosis, receptor-mediated), and Exocytosis.
  • Describe phagocytosis.
    Cell engulfs solid particles using pseudopods to form a phagosome, used by macrophages.
  • Describe pinocytosis.
    Nonspecific uptake of extracellular fluid and solutes by plasma membrane infolding.
  • What is receptor-mediated endocytosis?
    Selective uptake of molecules binding to specific membrane receptors.
  • How does exocytosis work?
    Secretory vesicles fuse with the plasma membrane to eject substances like hormones and neurotransmitters.