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Cell Membrane Structure and Transport Mechanisms

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Termini in questo insieme (20)

  • What is the Fluid Mosaic Model of the cell membrane?
    The membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a bilayer of amphipathic phospholipids.
  • What are the main components of the cell membrane?
    Mainly amphipathic phospholipids forming a bilayer, with embedded proteins, cholesterol, and carbohydrates.
  • What does amphipathic mean in the context of phospholipids?
    Having both hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.
  • Why is membrane fluidity important?
    It allows lipids and proteins to move sideways, enabling membrane flexibility, protein function, and cell signaling.
  • What types of proteins are found in the membrane mosaic?
    Integral (including transmembrane) proteins and peripheral proteins.
  • What functions do membrane proteins perform?
    Transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to cytoskeleton and extracellular matrix.
  • What is selective permeability of the plasma membrane?
    The membrane controls the exchange of substances, allowing some molecules to cross more easily than others.
  • Which molecules cross the membrane easily without transport proteins?
    Hydrophobic (nonpolar) molecules like CO2 and O2.
  • How do hydrophilic (polar) molecules cross the membrane?
    They generally require specific transport proteins such as channels or carriers.
  • What is diffusion in passive transport?
    The movement of substances down their concentration gradient from high to low concentration without energy use.
  • What is osmosis?
    The diffusion of water across a selectively permeable membrane from low to high solute concentration.
  • Define isotonic, hypotonic, and hypertonic solutions relative to a cell.
    Isotonic: solute concentration equal inside and outside; Hypotonic: lower solute outside, water enters cell; Hypertonic: higher solute outside, water leaves cell.
  • What happens to animal cells in hypotonic solutions?
    Water enters the cell, causing it to swell and possibly lyse.
  • How do plant cells respond to hypotonic solutions?
    They swell until the cell wall exerts turgor pressure, preventing bursting.
  • What is facilitated diffusion?
    Passive transport of molecules across the membrane via specific channel or carrier proteins.
  • How do channel proteins function?
    They form hydrophilic channels that allow specific molecules or ions to pass through the membrane.
  • How do carrier proteins function in facilitated diffusion?
    They change shape to transport specific solutes across the membrane.
  • What is active transport?
    The movement of molecules against their concentration gradient using energy, often ATP.
  • Give an example of active transport in cells.
    The sodium-potassium pump, which pumps sodium out and potassium into the cell using ATP.
  • What is cotransport?
    A transport mechanism where a membrane protein couples the downhill diffusion of one solute to the uphill transport of another.