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General Biology: Cell Membranes and Lipids

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이 집합의 용어 (20)

  • What is the primary function of the cell membrane?
    The cell membrane regulates exchanges between the cell and its environment, controlling inbound and outbound traffic.
  • Describe the fluid mosaic model of the cell membrane.
    The fluid mosaic model depicts the membrane as a fluid phospholipid bilayer with embedded proteins that move laterally.
  • What are the main components of a phospholipid molecule?
    A phospholipid has a hydrophilic head (choline, phosphate, glycerol) and two hydrophobic fatty acid tails.
  • Why are phospholipids described as amphipathic?
    Phospholipids have both hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.
  • What types of molecules can easily diffuse across the plasma membrane?
    Small, nonpolar molecules like O2, CO2, and small polar molecules like H2O can diffuse easily.
  • Why do large polar molecules have difficulty crossing the membrane?
    Large polar molecules like glucose and ions cannot easily cross due to the hydrophobic core of the membrane.
  • What is osmosis?
    Osmosis is the diffusion of water across a selectively permeable membrane from low to high solute concentration.
  • How does a hypotonic solution affect animal and plant cells?
    Animal cells may lyse (burst), while plant cells become turgid (normal) due to water intake.
  • What is the role of transport proteins in the membrane?
    Transport proteins facilitate the movement of molecules that cannot diffuse freely, via passive or active transport.
  • What distinguishes active transport from passive transport?
    Active transport requires energy (ATP) to move molecules against their concentration gradient; passive transport does not.
  • What is the significance of cholesterol in the plasma membrane?
    Cholesterol modulates membrane fluidity and stability in animal cell membranes.
  • Describe the difference between Gram-positive and Gram-negative bacterial cell walls.
    Gram-positive bacteria have a thick peptidoglycan layer with lipoteichoic acids; Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane with lipopolysaccharides.
  • What is the S-layer in archaeal cells?
    The S-layer is a proteinaceous cell wall layer found in archaea, providing structural support outside the cytoplasmic membrane.
  • What is the function of perforin used by cytotoxic T lymphocytes (CTLs)?
    Perforin forms pores in target cell membranes to enable entry of granzymes, leading to cell death.
  • How do phagocytes use perforin-2 differently from CTLs?
    Phagocytes use perforin-2 to target and kill microbes inside phagosomes, unlike CTLs which target infected or cancerous cells.
  • What is the significance of the phospholipid bilayer thickness and pore size in membrane proteins?
    Membrane proteins have hydrophobic regions matching bilayer thickness; pores allow selective passage of molecules.
  • What is the role of vesicles in membrane transport?
    Vesicles mediate bulk transport via endocytosis (inward) and exocytosis (outward) of large molecules.
  • What is the difference between simple diffusion and facilitated diffusion?
    Simple diffusion occurs directly through the membrane; facilitated diffusion requires transport proteins.
  • How does the plasma membrane contribute to cell signaling?
    Membrane proteins receive signals from outside, triggering intracellular responses and communication.
  • What is the role of glycolipids and glycoproteins in the membrane?
    They contribute to cell recognition, signaling, and membrane stability on the extracellular side.